Note: Descriptions are shown in the official language in which they were submitted.
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Heater pattern including heaters powered by wind-electricity for in situ
thermal
processing of a subsurface hydrocarbon-containing formation
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a continuation-in-part of PCT/US13/38089 filed on April
24, 2013. This application
claims priority to US 61/729,628 filed on November 25, 2012.
FIELD OF THE INVENTION
The present invention relates to methods and systems of heating a subsurface
formation, for
example, in order to produce hydrocarbon fluids therefrom.
DESCRIPTION OF RELATED ART
Hydrocarbons obtained from subterranean formations are often used as energy
resources, as
feedstocks, and as consumer products. Concerns over depletion of available
hydrocarbon resources and
concerns over declining overall quality of produced hydrocarbons have led to
development of processes
for more efficient recovery, processing and/or use of available hydrocarbon
resources. In situ processes
may be used to remove hydrocarbon materials from subterranean formations that
were previously
inaccessible and/or too expensive to extract using available methods. Chemical
and/or physical
properties of hydrocarbon material in a subterranean formation may need to be
changed to allow
hydrocarbon material to be more easily removed from the subterranean formation
and/or increase the
value of the hydrocarbon material. The chemical and physical changes may
include in situ reactions that
produce removable fluids, composition changes, solubility changes, density
changes, phase changes,
and/or viscosity changes of the hydrocarbon material in the formation.
Large deposits of heavy hydrocarbons (heavy oil and/or tar) contained in
relatively permeable
formations (for example in tar sands) are found in North America, South
America, Africa, and Asia. Tar
can be surface-mined and upgraded to lighter hydrocarbons such as crude oil,
naphtha, kerosene, and/or
gas oil. Surface milling processes may further separate the bitumen from sand.
The separated bitumen
may be converted to light hydrocarbons using conventional refinery methods.
Mining and upgrading tar
sand is usually substantially more expensive than producing lighter
hydrocarbons from conventional oil
reservoirs.
Retorting processes for oil shale may be generally divided into two major
types: aboveground
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(surface) and underground (in situ). Aboveground retorting of oil shale
typically involves mining and
construction of metal vessels capable of withstanding high temperatures. The
quality of oil produced
from such retorting may typically be poor, thereby requiring costly upgrading.
Aboveground retorting
may also adversely affect environmental and water resources due to mining,
transporting, processing,
and/or disposing of the retorted material. Many U.S. patents have been issued
relating to aboveground
retorting of oil shale. Currently available aboveground retorting processes
include, for example, direct,
indirect, and/or combination heating methods.
In situ retorting typically involves retorting oil shale without removing the
oil shale from the
ground by mining. Modified in situ processes typically require some mining to
develop underground
retort chambers. An example of a "modified" in situ process includes a method
developed by Occidental
Petroleum that involves mining approximately 20% of the oil shale in a
formation, explosively
rubblizing the remainder of the oil shale to fill up the mined out area, and
combusting the oil shale by
gravity stable combustion in which combustion is initiated from the top of the
retort. Other examples of
"modified" in situ processes include the "Rubble In Situ Extraction" ("RISE")
method developed by the
Lawrence Livermore Laboratory ("LLL") and radio-frequency methods developed by
ITT Research
Institute ("IITRI") and LLL, which involve tunneling and mining drifts to
install an array of
radio-frequency antennas in an oil shale formation.
Obtaining permeability in an oil shale formation between injection and
production wells tends to
be difficult because oil shale is often substantially impermeable. Drilling
such wells may be expensive
and time consuming. Many methods have attempted to link injection and
production wells.
Many different types of wells or wellbores may be used to treat the
hydrocarbon-containing
formation using an in situ heat treatment process. In some embodiments,
vertical and/or substantially
vertical wells are used to treat the formation. In some embodiments,
horizontal or substantially
horizontal wells (such as J-shaped wells and/or L-shaped wells), and/or U-
shaped wells are used to treat
the formation. In some embodiments, combinations of horizontal wells, vertical
wells, and/or other
combinations are used to treat the formation. In certain embodiments, wells
extend through the
overburden of the formation to a hydrocarbon-containing layer of the
formation. In some situations, heat
in the wells is lost to the overburden. In some situations, surface and
overburden infrastructures used to
support heaters and/or production equipment in horizontal wellbores or U-
shaped wellbores are large in
size and/or numerous.
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Wellbores for heater, injection, and/or production wells may be drilled by
rotating a drill bit
against the formation. The drill bit may be suspended in a borehole by a drill
string that extends to the
surface. In some cases, the drill bit may be rotated by rotating the drill
string at the surface. Sensors may
be attached to drilling systems to assist in determining direction, operating
parameters, and/or operating
conditions during drilling of a wellbore. Using the sensors may decrease the
amount of time taken to
determine positioning of the drilling systems. For example, U.S. Pat. No.
7,093,370 to Hansberry and
U.S. Patent Application Publication No. 2009-027041 to Zaeper et al, both of
which are incorporated
herein by reference, describe a borehole navigation systems and/or sensors to
drill wellbores in
hydrocarbon formations. At present, however, there are still many hydrocarbon-
containing formations
where drilling wellbores is difficult, expensive, and/or time consuming.
Heaters may be placed in wellbores to heat a formation during an in situ
process. There are many
different types of heaters which may be used to heat the formation. Examples
of in situ processes
utilizing downhole heaters are illustrated in U.S. Pat. No. 2,634,961 to
Ljungstrom; U.S. Pat. No.
2,732,195 to Ljungstrom; U.S. Pat. No. 2,780,450 to Ljungstrom; U.S. Pat. No.
2,789,805 to Ljungstrom;
U.S. Pat. No. 2,923,535 to Ljungstrom; U.S. Pat. No. 4,886,118 to Van Meurs et
al.; and U.S. Pat. No.
6,688,387 to Wellington et al.; each of which is incorporated by reference as
if fully set forth herein.
As discussed above, there has been a significant amount of effort to develop
methods and systems
to economically produce hydrocarbons, hydrogen, and/or other products from
hydrocarbon-containing
formations. At present, however, there are still many hydrocarbon-containing
formations from which
hydrocarbons, hydrogen, and/or other products cannot be economically produced.
Thus, there is a need
for improved methods and systems for heating of a hydrocarbon formation and
production of fluids from
the hydrocarbon formation. There is also a need for improved methods and
systems that reduce energy
costs for treating the formation, reduce emissions from the treatment process,
facilitate heating system
installation, and/or reduce heat loss to the overburden as compared to
hydrocarbon recovery processes
that utilize surface based equipment.
SUMMARY OF EMBODIMENTS
Embodiments of the present invention relate to heater patterns and related
methods of producing
hydrocarbon fluids from a subsurface hydrocarbon-containing formation (for
example, an oil shale
formation) where a heater cell may be divided into nested inner and outer
zones. One or more heaters of
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the heater cell are powered primarily by electricity generated by wind.
Production wells may be located
within one or both zones. In the smaller inner zone, heaters are arranged at a
relatively high spatial
density while in the larger surrounding outer zone, a heater spatial density
is significantly lower. Due to
the higher heater density, a rate of temperature increase in the smaller inner
zone of the subsurface
exceeds that of the larger outer zone, and a rate of hydrocarbon fluid
production ramps up significantly
faster in the inner zone than in the outer zone.
The overall density of heaters in the heater cell, considered as a whole, is
significantly less than
that within the inner zone. Thus, the number of heaters required for the
heater pattern is substantially less
than what would be required if the heater density throughout the heater cell
was that within the inner
zone.
In a first embodiment related to heater patterns and wind electricity, at
least a majority (in some
embodiments, at least two-thirds) of heaters of the inner zone are powered
primarily by wind electricity
while at least a majority (in some embodiments, at least two-thirds) of
heaters of the outer zone are
powered primarily by fuel combustion. This may be useful, for example, in
remote locations with
minimal infrastructure where it is relatively easy to install wind turbines
despite their expense. Almost
immediately after installing the wind turbines and associated inner-zone
heaters, it is possible to
commence heating of at least the inner zone with minimal delay. At a later
time, for example, when
combustible pyrolysis gas from the inner zone is available or when appropriate
infrastructure is available,
it is possible to rely on this pyrolysis gas or infrastructure (e.g. a power
plant) to supply energy to the
outer zone heaters.
The second embodiment relates to the opposite situation. In the second
embodiment, (i) at least
a majority (e.g. at least half, or at least two-thirds) of heaters of the
inner zone are powered primarily by
fossil fuel electricity or by fossil fuel combustion and (ii) at least a
majority (e.g. at least half, or at least
two-thirds) of heaters of the outer zone are powered primarily by wind
electricity. Because the outer zone
heaters typically operate for a significantly longer period of time, the
second embodiment is particularly
advantageous for minimizing CO2 footprint. In the inner zone, a
reliable/continuous energy source is
important (i.e. rather than relying on intermittent wind or solar), so as to
ensure early production of
hydrocarbon production from the formation. In this second embodiment, most
inner zone heaters
therefore derive their power from fossil fuels as opposed to from intermittent
sources. Thus ensures that
the inner zone heats up quickly and minimizes a time delay before production
begins.
In both of these embodiments, thermal energy from the inner zone may migrate
outwardly to the
outer zone so as to accelerate hydrocarbon fluid production in the outer zone.
Despite the significantly
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lower heater density in the outer zone, a rate of hydrocarbon fluid production
in the outer zone may ramp
up fast enough so that the overall rate of hydrocarbon fluid production for
the heater cell as a whole is
substantially sustained, over an extended period of time, once the inner zone
production rate has peaked.
5
As such, the heater patterns disclosed herein provide the minimal, or
nearly the minimal, rise time
to a substantially sustained production rate that is possible for a given
number of heaters. Alternatively, it
may be said that the heater patterns disclosed herein minimize, or nearly
minimize, the number of heaters
required to achieve a relatively fast rise time with a sustained production
level.
In some embodiments, a heater spacing within the outer zone is about twice
that of the inner zone
and/or a heater density within the inner zone is about three times that of the
outer zone and/or an average
distance, in the inner zone, to a nearest heater is about 2-3 times that
within the outer zone. In some
embodiments, an area of a region enclosed by a perimeter of the outer zone is
between two and seven (e.g.
at least two or at least three and/or at most seven or at most six or at most
five) times (for example, about
four times) that enclosed by a perimeter of the inner zone.
In some embodiments, the inner zone, outer zone or both are shaped as a
regular hexagon. This
shape may be particularly useful when heater cells are arranged on a two-
dimensional lattice so as to fill
a two-dimensional portion of the subsurface while eliminating or substantially
minimizing the size of the
interstitial space between neighboring heater cells. As such, a number of
heater cells may entirely, or
almost entirely, cover a portion of the sub-surface.
Some embodiments of the present invention relate to 'two-level' heater
patterns where an inner
zone of heaters at a higher density is nested within an outer zone of heaters
at a lower density. This
concept may be generalized to N-level heater patterns where one or more
'outer' zones of heaters
surround a relatively heater-dense inner zone of heaters. In one example, N=2.
In another example, N=3.
In yet another example, N=4.
For each pair of heater zones, the more outer heater zone is larger than the
more inner heater zone.
Although the heater density in the more outer heater zone is significantly
less than that in the more inner
zone, and although the hydrocarbon fluid production peak in the inner zone
occurs at a significantly
earlier time than in the more outer zone, sufficient thermal energy is
delivered to the more outer zone so
once the production rate in the more inner zone ramps up quickly, this rate
may be substantially sustained
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for a relatively extended period of time by hydrocarbon fluid production rate
in the more outer zone.
In some embodiments, further performance improvements may be achieved by: (i)
concentrating
electrical heaters in the denser inner zone while the heaters of the outer
zone are primarily molten salt
heaters; and/or (ii) significantly reducing a power output of the inner-zone
heater after an inner zone
hydrocarbon fluid production rate has dropped (e.g. by a first minimal
threshold fraction) from a
maximum level; and/or (iii) substantially shutting off one or more inner zone
production wells after the
inner zone hydrocarbon fluid production rate has dropped (e.g. by a second
minimal threshold fraction
equal to or differing from the first minimal threshold fraction) from a
maximum level; and/or (iv)
injecting heat-transfer fluid into the inner zone (e.g. via inner zone
production well(s) and/or via inner
zone injection well(s)) so as to accelerate the outwardly migration of thermal
energy from the inner zone
to the outer zone ¨ for example, by supplementing outwardly-directed diffusive
heater transfer with
outwardly-directed convective heat transfer.
It is now disclosed a system for in-situ production of hydrocarbon fluids from
a subsurface
hydrocarbon-containing formation, the system comprising: a heater cell divided
into nested inner and
outer zones such that an enclosed area ratio between respective areas enclosed
by substantially-convex
polygon-shaped perimeters of the outer and inner zones is between two and
seven, heaters being located
at all polygon vertices of inner and outer zone perimeters, inner zone and
outer zone heaters being
respectively distributed around inner and outer zone centroids such that an
average heater spacing in
outer zone significantly exceeds that of inner zone, at least a majority of
the heaters in the inner zone
being powered primarily by fuel combustion and at least a majority of heaters
in the outer zone being
powered primarily by electricity generated by wind.
It is now disclosed a system for in-situ production of hydrocarbon fluids from
a subsurface
hydrocarbon-containing formation, the system comprising: a heater cell divided
into nested inner and
outer zones such that an enclosed area ratio between respective areas enclosed
by substantially-convex
polygon-shaped perimeters of the outer and inner zones is between two and
seven, heaters being located
at all polygon vertices of inner and outer zone perimeters, inner zone and
outer zone heaters being
respectively distributed around inner and outer zone centroids such that an
average heater spacing in
outer zone significantly exceeds that of inner zone, at least a majority of
the heaters in the inner zone
being powered primarily by fuel combustion and at least a majority of heaters
in the outer zone being
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powered primarily by electricity generated by wind.
It is now disclosed a system for in-situ production of hydrocarbon fluids from
a subsurface
hydrocarbon-containing formation, the system comprising: a heater cell divided
into nested inner and
outer zones such that an enclosed area ratio between respective areas enclosed
by substantially-convex
polygon-shaped perimeters of the outer and inner zones is between two and
seven, heaters being located
at all polygon vertices of inner and outer zone perimeters, inner zone and
outer zone heaters being
respectively distributed around inner and outer zone centroids such that a
heater spatial density in inner
zone significantly exceeds that of outer zone, at least a majority of the
heaters in the inner zone being
powered primarily by fuel combustion and at least a of heaters in the outer
zone being powered primarily
by electricity generated by wind.
It is now disclosed a system for in-situ production of hydrocarbon fluids from
a subsurface
hydrocarbon-containing formation, the system comprising: heaters arranged in a
target portion of the
formation, the target portion being divided into nested inner and outer zones
heaters so that inner zone
and outer zone heaters are respectively distributed around inner and outer
zone centroids, at least a
majority of the heaters in the inner zone being powered primarily by fuel
combustion and at least a
majority of heaters in the outer zone being powered primarily by electricity
generated by wind.
It is now disclosed a system for in-situ production of hydrocarbon fluids from
a subsurface
formation, the system comprising: (i) heaters powered primarily by fuel
combustion and (ii) heaters
powered primarily by electricity generated by wind arranged within a target
portion of the sub-surface
formation.
In some embodiments, within the target formation, a first heater that is
powered primarily by fuel
combustion is located at most 50 meters from a second heater that is powered
primarily by electricity
generated by wind.
In some embodiments, within the target formation, a first heater that is
powered primarily by fuel
combustion is located at most 35 meters from a second heater that is powered
primarily by electricity
generated by wind.
In some embodiments, within the target formation, a first heater that is
powered primarily by fuel
combustion is located at most 20 meters from a second heater that is powered
primarily by electricity
generated by wind.
In some embodiments, within the target formation, a first heater that is
powered primarily by fuel
combustion is located at most 10 meters from a second heater that is powered
primarily by electricity
generated by wind.
In some embodiments, within the target formation, a first heater that is
powered primarily by fuel
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combustion is located at most 5 meters from a second heater that is powered
primarily by electricity
generated by wind.
In some embodiments, within the target formation, the average separation
distance between
neighboring heaters that are each powered primarily by electricity generated
by wind exceeds the
average separation distance between neighboring heaters that are each powered
primarily by fuel
combustion.
In some embodiments, within the target formation, the average separation
distance between
neighboring heaters that are each powered primarily by electricity generated
by wind significantly
exceeds the average separation distance between neighboring heaters that are
each powered primarily by
fuel combustion.
In some embodiments, within the target formation, the average separation
distance between
neighboring heaters that are each powered primarily by electricity generated
by wind significantly is
about twice the average separation distance between neighboring heaters that
are each powered primarily
by fuel combustion.
In some embodiments, at least some, or at least a majority, or at least
two¨thirds of the heaters
powered primarily by fuel combustion are electrical heaters that are powered
primarily by electricity
generated by fuel combustion.
In some embodiments, at least some, or at least a majority, or at least
two¨thirds of the heaters
powered primarily by fuel combustion are combustion heaters where a combusted
gas circulated in the
subsurface.
In some embodiments, at least some, or at least a majority, or at least
two¨thirds of the heaters
powered primarily by fuel combustion are electrical heaters wherein a material
is resistively heated by
electricity generated by fuel combustion.
In some embodiments, at least some, or at least a majority, or at least
two¨thirds of the heaters
powered primarily by fuel combustion are advection heaters where a material,
that is in thermal
communication with a circulating heat transfer fluid flowing in the
subsurface, is heated resistively by
electricity generated by fuel combustion.
In some embodiments, the resistively heated material is in the subsurface.
In some embodiments, the resistively heated material is above the surface.
In some embodiments, at least some, or at least a majority, or at least
two¨thirds of the heaters
powered primarily by electricity generated by wind are electrical heaters
wherein a material is
resistively heated by electricity generated by wind.
In some embodiments, at least some, or at least a majority, or at least
two¨thirds of the heaters
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powered primarily by electricity generated by wind are advection heaters where
a material, that is in
thermal communication with a circulating heat transfer fluid flowing in the
subsurface, is heated
resistively by electricity generated by wind.
In some embodiments, the resistively heated material is in the subsurface.
In some embodiments, the resistively heated material is above the surface.
In some embodiments, wherein two-thirds of the heaters in the inner zone are
powered primarily
by fuel combustion and at least two-thirds of heaters in the outer zone being
powered primarily by
electricity generated by wind.
It is now disclosed a method of in-situ production of hydrocarbon fluids in a
subsurface
hydrocarbon-containing formation, the method comprising: a. during an earlier
stage of production,
producing hydrocarbon fluids primarily in a first portion of the target region
that is heated primarily by
thermal energy derived from combustion of fuel; and b. during a later stage of
production, producing
hydrocarbon fluid primarily in a second portion of the target region that is
heated primarily by thermal
energy derived from electricity generated by wind, wherein at least some of
the thermal energy required
for hydrocarbon fluid production in the second portion of the target region is
supplied by outward
migration of thermal energy from the first portion to the second portion of
the target region.
It is now disclosed a method of in-situ production of hydrocarbon fluids in a
subsurface
hydrocarbon-containing formation, the method comprising: a. during an earlier
stage of production,
producing hydrocarbon fluids primarily in a first portion of the target region
that is heated primarily by
thermal energy derived from electricity generated by wind and b. during a
later stage of production,
producing hydrocarbon fluid primarily in a second portion of the target region
that is heated primarily by
thermal energy derived from combustion of fuel wherein at least some of the
thermal energy required for
hydrocarbon fluid production in the second portion of the target region is
supplied by outward migration
of thermal energy from the first portion to the second portion of the target
region.
It is now disclosed a system for in-situ production of hydrocarbon fluids from
a subsurface
hydrocarbon-containing formation, the system comprising: a heater cell divided
into nested inner and
outer zones such that an enclosed area ratio between respective areas enclosed
by substantially-convex
polygon-shaped perimeters of the outer and inner zones is between two and
seven, heaters being located
at all polygon vertices of inner and outer zone perimeters, inner zone and
outer zone heaters being
respectively distributed around inner and outer zone centroids such that an
average heater spacing in
outer zone significantly exceeds that of inner zone, at least a majority of
the heaters in the inner zone
being powered primarily by electricity generated by wind and at least a
majority of heaters in the outer
zone being powered primarily by fuel combustion.
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It is now disclosed a system for in-situ production of hydrocarbon fluids from
a subsurface
hydrocarbon-containing formation, the system comprising: a heater cell divided
into nested inner and
outer zones such that an enclosed area ratio between respective areas enclosed
by substantially-convex
polygon-shaped perimeters of the outer and inner zones is between two and
seven, heaters being located
5 at all polygon vertices of inner and outer zone perimeters, inner zone
and outer zone heaters being
respectively distributed around inner and outer zone centroids such that an
average heater spacing in
outer zone significantly exceeds that of inner zone, at least a majority of
the heaters in the inner zone
being powered primarily by electricity generated by wind and at least a
majority of heaters in the outer
zone being powered primarily by fuel combustion.
10 It is now disclosed a system for system for in-situ production of
hydrocarbon fluids from a
subsurface hydrocarbon-containing formation, the system comprising: a heater
cell divided into nested
inner and outer zones such that an enclosed area ratio between respective
areas enclosed by
substantially-convex polygon-shaped perimeters of the outer and inner zones is
between two and seven,
heaters being located at all polygon vertices of inner and outer zone
perimeters, inner zone and outer
zone heaters being respectively distributed around inner and outer zone
centroids such that a heater
spatial density in inner zone significantly exceeds that of outer zone, at
least a majority of the heaters in
the inner zone being powered primarily by electricity generated by wind and at
least a majority of
heaters in the outer zone being powered primarily by fuel combustion.
It is now disclosed a system for in-situ production of hydrocarbon fluids from
a subsurface
hydrocarbon-containing formation, the system comprising: heaters arranged in a
target portion of the
formation, the target portion being divided into nested inner and outer zones
heaters so that inner zone
and outer zone heaters are respectively distributed around inner and outer
zone centroids, at least a
majority of the heaters in the inner zone being powered primarily by
electricity generated by wind and at
least a majority of heaters in the outer zone being powered primarily by fuel
combustion.
In some embodiments, at least two-thirds of the heaters in the inner zone are
powered primarily
by electricity generated by wind and at least two-thirds of heaters in the
outer zone being powered
primarily by fuel combustion.
In some embodiments, a centroid of the inner zone is located in a central
portion of the region
enclosed by a perimeter of the outer zone . In some embodiments, each heater
cell includes at least one
production well located within the inner zone . In some embodiments, each
heater cell includes at least
one production well located within the outer zone . In some embodiments, a
production well spatial
density in the inner zone at least exceeds that of the outer zone . In some
embodiments, an average heater
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spacing in outer zone is at least about twice that of inner zone. In some
embodiments, the area ratio
between respective areas enclosed by inner zone and outer zone perimeters is
about four, and an average
heater spacing in the outer zone is about twice that of the inner zone. In
some embodiments, a spacing
ratio between an average heater spacing of the outer zone and that of the
inner zone is about equal to a
square root of the area ratio between respective areas enclosed by the inner
zone and outer zone
perimeters. In some embodiments, a spacing ratio between an average heater
spacing of the outer zone
and that of the inner zone is about equal to a square root of the area ratio
between respective areas
enclosed by inner zone and outer zone perimeters. In some embodiments, a
heater spatial density in the
inner zone is at least about twice that of outer zone. In some embodiments, a
heater spatial density in the
inner zone is at least twice that of the outer zone. In some embodiments, a
heater spatial density in the
inner zone is at least about three times that of the outer zone. In some
embodiments, a heater density
ratio between a heater spatial densities in the inner zone and that of outer
zone is substantially equal to an
area ratio between an area of the outer zone and that of the inner zone.
In some embodiments, for an area ratio between an area enclosed by a perimeter
of outer zone to
that enclosed by a perimeter of inner zone is at most six or at most five
and/or at least 3.5
In some embodiments, the one or more heater cells include first and second
heater cells having
substantially the same area and sharing at least one common heater-cell-
perimeter heater.
In some embodiments, the one or more heater cells further includes a third
heater cell having
substantially the same area as the first and second heater cells, the third
heater cell sharing at least one
common heater-cell-perimeter heater with the first heater cell, the second and
third heater cells located
substantially on opposite sides of the first heater cell.
In some embodiments, a given heater cell of the heater cells is substantially
surrounded by a
plurality of neighboring heater cells.
In some embodiments, a given heater cell of the heater cells is substantially
surrounded by a
plurality of neighboring heater cells and the given heater cell shares a
common heater-cell-perimeter
heater with each of the neighboring heater cells.
In some embodiments, inner zone heaters are distributed substantially
uniformly throughout the
inner zone.
In some embodiments, each heater cell being arranged so that within the outer
zone, heaters are
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predominantly located on the outer zone perimeter.
In some embodiments, at least one of the inner and outer perimeters is shaped
like a regular
hexagon, like a lozenge, or like a rectangle.
In some embodiments, the inner and outer perimeters are similar shaped.
In some embodiments, within the inner and/or outer zones, a majority of
heaters are disposed on
a triangular, hexagonal or rectangular grid.
In some embodiments, a total number of inner zone heaters exceeds that of the
outer zone.
In some embodiments, a total number of inner zone heaters exceeds that of the
outer zone by at
least 50%.
In some embodiments, at least five inner zone heaters are dispersed throughout
the inner zone.
In some embodiments, at least five or at least seven or at least ten outer
zone heaters are located
around a perimeter of the outer zone.
In some embodiments, at least one-third of at least one-half of inner zone
heaters are not located
on the inner zone perimeter.
In some embodiments, for each of the inner zone and outer zone perimeters, an
aspect ratio is less
than 2.5.
In some embodiments, at least five or at least seven or at least ten heaters
are distributed about the
perimeter of the inner zone .
In some embodiments, a majority of the heaters in the inner zone are
electrical heaters and a
majority of the heaters in the outer zone are molten salt heaters.
In some embodiments, at least two-thirds or at least three-quarters of inner-
zone heaters are
electrical heaters and at least two-thirds of outer-zone heaters are molten
salt heaters.
In some embodiments, the system further includes control apparatus configured
to regulate heater
operation times so that, on average, heaters in the outer zone operate above a
one-half maximum power
level for at least twice as long as the heaters in the inner zone.
In some embodiments, the control apparatus is configured so that on average,
the outer zone
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heaters operate above a one-half maximum power level for at least three times
as long as the inner zone
heaters.
In some embodiments, an average inner-zone heater spacing is between 1 and 10
meters (for
example, between 1 and 5 meters or between 1 and 3 meters).
In some embodiments, the heaters are configured to pyrolize the entirety of
both the inner and
outer zones.
In some embodiments, the heaters are configured to heat respective substantial
entirety of the
inner and outer regions to substantially the same uniform temperature.
In some embodiments, among the inner zone heaters and/or outer zone heaters
and/or inner
perimeter heaters and/or outer perimeter heaters, a ratio between a standard
deviation of the spacing and
an average spacing is at most 0.2.
In some embodiments, all heaters have substantially the same maximum power
level and/or
substantially the same diameter.
In some embodiments, a ratio between the area of the inner zone and a square
of an average
distance to a nearest heater within the inner zone is at least 80.
In some embodiments, a ratio between the area of the inner zone and a square
of an average
distance to a nearest heater within the inner zone is at least 60 or at least
70 or at least 80 or at least 90 or
at least 100.
In some embodiments,inner and outer zones respective have polygon-shaped
perimeters, such
that heaters are located at all polygon vertices of inner and outer zone
perimeters.
In some embodiments, the inner zone is substantially-convex.
In some embodiments, the outer zone is substantially-convex.
In some embodiments, an average heater spacing in the outer zone significantly
exceeds that of the
inner zone.
In some embodiments, an average heater spacing in the outer zone is about
twice that of the inner
zone.
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In some embodiments, a spacing ratio between an average heater spacing of the
outer zone and that
of the inner zone is about equal to a square root of the area ratio between
respective areas enclosed by the
inner zone and outer zone perimeters, .
In some embodiments, a heater spatial density in inner zone significantly
exceeds that of the outer
zone.
In some embodiments, wherein a heater spatial density in the inner zone is at
least twice that of the
outer zone.
In some embodiments, a heater spatial density in inner zone is at least about
three times that of the
outer zone.
In some embodiments, a heater density ratio between a heater spatial densities
in inner that of
outer zones is substantially equal to a zone area ratio between an area of
outer zone and that of inner
zone.
In some embodiments, an average distance to a nearest heater within the outer
zone significantly
exceeds that of the inner zone.
In some embodiments, an average distance to a nearest heater within the outer
zone is between two
and three times that of the inner zone.
In some embodiments, an average distance to a nearest heater on a perimeter of
the inner zone is at
most substantially equal to that within inner zone.
In some embodiments, an average distance to a nearest heater on the outer zone
perimeter is equal
to at most about twice that on the inner zone perimeter.
In some embodiments, the system further comprises at least one inner zone
production well within
inner zone and at least one outer zone production well within outer zone.
In some embodiments, a production well spatial density in inner zone exceeds
that of outer zone.
In some embodiments, a production well spatial density in inner zone is equal
to about three times
of outer zone.
In some embodiments, a majority of the outer zone heaters are arranged on a
perimeter of the outer
zone.
In some embodiments, heaters are located at all polygon vertices of inner and
outer zone
perimeters.
In some embodiments, heaters are located at all vertices of the OZS additional
zone perimeter.
In some embodiments, an average distance to a nearest heater within the outer
zone is equal to
between about two and about three times that of the inner zone.
In some embodiments, an average distance to a nearest heater within the outer
zone is equal to
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between two and three times that of the inner zone.
In some embodiments, for each of the zone pairs, a heater spacing of the more
outer zone is at least
about twice that of the more inner zone.
In some embodiments, for each of the zone pairs, the area ratio between
respective more outer and
5
more inner zones is about four, and a heater spacing of the more outer
zone is about twice that of the more
inner zone.
In some embodiments, for each of the zone pairs, ratio between a heater
spacing of the more outer
zone and that of the more inner zone is substantially equal to square root of
the area ratio between the
more outer and the more inner zones of the zone pair.
10
In some embodiments, for each of the zone pairs, the area ratio between
respective areas enclosed
by perimeters of the more outer zone and the more inner zone is at most six.
In some embodiments, for each of the zone pairs, the area ratio between
respective areas enclosed
by perimeters of the more outer zone and the more inner zone is at most five.
In some embodiments, for each of the zone pairs, the area ratio between
respective areas enclosed
15 by perimeters of the more outer zone and the more inner zone is at least
2.5.
In some embodiments, a significant majority of the inner zone heaters are
located away from outer
zone perimeter.
In some embodiments, a significant majority of the outer zone heaters are
located away from a
perimeter of outer-zone-surrounding (OZS) additional zone.
In some embodiments, for each of the zone pairs, a heater spatial density of
the more inner zone is
equal to at least about twice that of the more outer zone.
In some embodiments, for each of the zone pairs, a heater spatial density of
the more inner zone is
equal to at most about six times that of the more outer zone.
In some embodiments, for each of the zone pairs, a centroid of the more inner
zone is located in a
central portion of the region enclosed by a perimeter of the more outer zone.
In some embodiments, for each of the zone pairs, an average distance to a
nearest heater in the
more outer zone is between about two and about three times that of the less
outer zone.
In some embodiments, for each of the zone pairs, an average distance to a
nearest heater in the
more outer zone is between two and three times that of the less outer zone.
In some embodiments, a centroid of inner zone is located in a central portion
of the region
enclosed by a perimeter of the outer zone .
In some embodiments, the heater cell includes at least one inner zone
production well located
within the inner zone.
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In some embodiments, the heater cell includes at least one outer zone
production well located
within the outer zone.
In some embodiments, the heater cell includes first and second outer zone
production wells located
within and on substantially on opposite sides of the outer zone.
In some embodiments, a production well spatial density in the inner zone at
least exceeds that of
the outer zone.
In some embodiments, an average heater spacing in outer zone is at least about
twice that of inner
zone.
In some embodiments, the area ratio between respective areas enclosed by inner
zone and outer
zone perimeters, is about four, and an average heater spacing in outer zone is
about twice that of inner
zone.
In some embodiments, a spacing ratio between an average heater spacing of the
outer zone and that
of the inner zone is about equal to a square root of the area ratio between
respective areas enclosed by the
inner zone and outer zone perimeters, .
In some embodiments, a spacing ratio between an average heater spacing of the
outer zone and that
of the inner zone is about equal to a square root of the area ratio between
respective areas enclosed by
inner zone and outer zone perimeters, .
In some embodiments, a heater spatial density in inner zone is at least about
twice that of outer
zone.
In some embodiments, a heater spatial density in inner zone is at least twice
that of outer zone.
In some embodiments, a heater spatial density in inner zone is at least about
three times that of the
outer zone.
In some embodiments, a heater density ratio between a heater spatial densities
in inner that of
outer zones is substantially equal to a zone area ratio between an area of
outer zone and that of inner
zone.
In some embodiments, an enclosed area ratio between an area enclosed by a
perimeter of outer
zone to that enclosed by a perimeter of inner zone is at most six or at most
five and/or at least 2.5 or at
least three or at least three.
In some embodiments, an average distance to a nearest heater in the outer zone
is between about
two and about three times that of the inner zone.
In some embodiments, an average distance to a nearest heater in the outer zone
is between two and
three times that of the inner zone .
In some embodiments, an average distance to a nearest heater on the inner zone
perimeter is
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substantially equal to that within inner zone.
In some embodiments, along the perimeter of outer zone, an average distance to
a nearest heater is
at most four times that along the perimeter of inner zone.
In some embodiments, along the perimeter of outer zone, an average distance to
a nearest heater is
at most three times that along the perimeter of inner zone.
In some embodiments, along the perimeter of outer zone, an average distance to
a nearest heater is
at most about twice that along the perimeter of inner zone.
In some embodiments, among outer-perimeter heaters located on the perimeter of
outer zone, an
average distance to a nearest heater significantly exceeds that among inner-
perimeter heaters located on
the perimeter of inner zone.
In some embodiments, among outer-perimeter heaters located on the perimeter of
outer zone, an
average distance to a second nearest heater significantly exceeds that among
inner-perimeter heaters
located on the perimeter of inner zone.
In some embodiments, the system includes a plurality of the heater cells,
first and second of the
heater cells having substantially the same area and sharing at least one
common heater-cell-perimeter
heater.
In some embodiments, wherein a third of the heater cells has substantially the
same area as the first
and second heater cells, the third heater cell sharing at least one common
heater-cell-perimeter heater
with the first heater cell, the second and third heater cells located
substantially on opposite sides of the
first heater cell.
In some embodiments, the system includes a plurality of the heater cells, at
least one of which is
substantially surrounded by a plurality of neighboring heater cells.
In some embodiments, a given heater cell of the heater cells is substantially
surrounded by a
plurality of neighboring heater cells and the given heater cell 608 shares a
common heater-cell-perimeter
heater with each of the neighboring heater cells.
In some embodiments, inner zone heaters are distributed substantially
uniformly throughout inner
zone.
In some embodiments, the heater cell is arranged so that within the outer
zone, heaters are
predominantly located on the outer zone perimeter.
In some embodiments, at least one of the inner and outer perimeters is shaped
like a regular
hexagon, like a lozenge, or like a rectangle.
In some embodiments, the inner and outer perimeters are like-shaped.
In some embodiments, within the inner and/or outer zones, a majority of
heaters are disposed on a
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triangular grid, hexagonal or rectangular grid.
In some embodiments, a total number of inner zone heaters exceeds that of the
outer zone.
In some embodiments, a total number of inner zone heaters exceeds that of the
outer zone by at
least 50%.
In some embodiments, at least five inner zone heaters are dispersed throughout
the inner zone.
In some embodiments, at least five or at least seven or at least ten outer
zone heaters are located
around a perimeter of outer zone.
In some embodiments, at least one-third of at least one-half of inner zone
heaters are not located on
inner zone perimeter.
In some embodiments, each of the inner zone and outer zone perimeters, has an
aspect ratio equal
to most 2.5.
In some embodiments, each of the inner zone and outer zone perimeters, has an
aspect ratio equal
to least 10.
In some embodiments, each of the inner zone and outer zone perimeters, is
shaped like a
rectangular.
In some embodiments, at least five or seven or nine heaters are distributed
about the perimeter of
inner zone and/or about the perimeter of the outer zone.
In some embodiments, at least ten heaters are distributed throughout inner
zone.
In some embodiments, a majority of the heaters in inner zone are electrical
heaters and a majority
of the heaters in outer zone are molten salt heaters.
In some embodiments, at least two-thirds or at least three-quarters of inner-
zone heaters are
electrical heaters and at least two-thirds of outer-zone heaters are molten
salt heaters.
In some embodiments, the system further includes control apparatus configured
to regulate heater
operation times so that, on average, heaters in outer zone operate above a one-
half maximum power
level for at least twice as long as the heaters in inner zone.
In some embodiments, the system includes control apparatus
configured to regulate heater operation times so that, on average, outer zone
heaters operate above
a one-half maximum power level for at least twice as long as the inner zone
heaters.
In some embodiments, the control apparatus is configured so that on average,
outer zone heaters
operate above a one-half maximum power level for at least three times as long
as the inner zone heaters.
In some embodiments, wherein an average inner-zone heater spacing is at most
20 meters or at
most 10 meters or at most 5 meters.
In some embodiments, an area of the inner zone is at most one square
kilometer.
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In some embodiments, an area of the inner zone is at most 500 square meters.
In some embodiments, the heaters are configured to induce pyrolysis throughout
substantial
entireties of both the inner and outer zones.
In some embodiments, the heaters are configured to heat respective substantial
entirety of the inner
and outer regions to substantially the same uniform temperature.
In some embodiments, among the inner zone heaters and/or outer zone heaters
and/or inner
perimeter heaters and/or outer perimeter heaters, a ratio between a standard
deviation of the spacing and
an average spacing is at most 0.2.
In some embodiments, all heaters have substantially the same maximum power
level and/or
substantially the same diameter.
In some embodiments, a ratio between the area of the inner zone and a square
of an average
distance to a nearest heater within the inner zone is at least 80 or at least
70 or at least 60 or at least 90.
In some embodiments, at most 10% or at most 7.6% or at most 5% or at most 4%
or at most 3% of
a length of the outer zone perimeter.
In some embodiments, an average distance to a nearest heater is at most one-
eighth or at most
one-tenth or at most one-twelfth of a square root of an area of the inner zone
.
In some embodiments, at most 30% or at most 20% or at most 10% of the inner
zone is displaced
from a nearest heater by length threshold equal to at most one quarter of a
square root of the inner zone.
In some embodiments, at most 10% of the inner zone is displaced from a nearest
heater by length
threshold equal to at most one quarter of a square root of the inner zone.
In some embodiments, the length threshold equals at most one fifth of a square
root of the inner
zone.
In some embodiments, an aspect ratio of the inner and/or outer zone is at most
four or most 3 or at
most 2.5.
In some embodiments, among the inner and outer zones, a ratio between a
greater aspect ratio and
a lesser aspect ratio is at most 1.5.
In some embodiments, an isoperimetric quotient of perimeters, of the inner
and/or outer zone is at
least 0.4 or at least 0.5 or at least 0.6.
In some embodiments, a perimeter of inner zone has a convex shape tolerance
value of at most 1.2
or at most 1.1.
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In some embodiments, heaters are arranged within inner zone so that inner zone
heaters are present
on every 72 degree sector or every 60 degree sector thereof for any reference
ray orientation.
5 BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 depicts a schematic view of an embodiment of a portion of the in situ
heat treatment system
for treating the hydrocarbon-containing formation.
FIGS. 2-3, 8-14, and 18-37 illustrate in-situ heater patterns in accordance
with various examples.
FIGS. 4-7 describe illustrative production functions for a two-level heater
cell.
10 FIGS. 15-17 illustrate various sub-surface heaters.
DETAILED DESCRIPTION OF EMBODIMENTS
For convenience, in the context of the description herein, various terms are
presented here. To the
15
extent that definitions are provided, explicitly or implicitly, here or
elsewhere in this application, such
definitions are understood to be consistent with the usage of the defined
terms by those of skill in the
pertinent art(s). Furthermore, such definitions are to be construed in the
broadest possible sense
consistent with such usage.
20
The following description generally relates to systems and methods for
treating hydrocarbons in
the formations. Such formations may be treated to yield hydrocarbon products,
hydrogen, and other
products.
Unless specified otherwise, for the present disclosure, when two quantities
QUANTi and QUANT2,
are 'about' equal to each other or 'substantially equal' to each other, the
quantities are either exactly
equal, or a 'quantity ratio' between (i) the greater of the two quantities
MAX(QUANTi, QUANT2) and (ii)
the lesser of the two quantities MIN(QUANTi, QUANT2) is at most 1.3. In some
embodiments, this ratio
is at most 1.2 or at most 1.1 or at most 1.05. In the present disclosure,
'about' equal and 'substantially
equal' are used interchangeably and have the same meaning.
An 'about-tolerance-parameter' governs an upper bound of the maximum
permissible deviation
between two quantities that are 'about equal.' The 'about-tolerance-parameter'
is defined as the
difference between the 'quantity ratio' defined in the previous paragraph and
1. Thus, unless otherwise
specified, a value of the 'about-tolerance-parameter' is 0.3 ¨ i.e. the
'quantity ratio' of the previous
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paragraph is at most 1.3. In some embodiments, the 'about-tolerance-parameter'
is 0.2 (i.e. the 'quantity
ratio' of the previous paragraph is at most 1.2 or 1.1 or 1.05). It is noted
that the
'about-tolerance-parameter' is a global parameter ¨ when the about tolerance
parameter is X then all
quantities that are 'about' or 'substantially' equal to each other have a
'quantity ratio' of about ]+X.
Unless specified otherwise, if heaters (or heater wells) are arranged "around"
a centroid of a
'candidate' region (e.g. an inner or outer or outer-zone-surrounding (OZS)
additional zone), then for
every 'reference ray orientation' (i.e. orientation of a ray from an origin),
heaters (i.e. centroids thereof in
a cross-section of the subsurface formation in which a heater pattern is
defined) are present within all
four quadrants (i.e. 90 degree sector) of the candidate region where the
'origin' is defined by the centroid
of the 'candidate region.' In some embodiments, heaters are present, for every
'reference ray
orientation,' within every 72 degree sector or on every 60 degree sector or on
every 45 sector of the
'candidate region.'
If heaters (or heater wells) are arranged 'around' a perimeter of a candidate
region, then they are
arranged 'around' the centroid of the candidate region and on a perimeter
thereof.
An "aspect ratio" of a shape refers to a ratio between its longer dimension
and its shorter
dimension.
In the context of reduced heat output heating systems, apparatus, and methods,
the term
"automatically" means such systems, apparatus, and methods function in a
certain way without the use of
external control (for example, external controllers such as a controller with
a temperature sensor and a
feedback loop, PID controller, or predictive controller).
A "centroid" of an object or region refers to the arithmetic mean of all
points within the object or
region. Unless specified otherwise, the 'object' or 'region' for which a
centroid is specified or computed
actually refers to a two-dimensional cross section of an object or region
(e.g. a region of the subsurface
formation). A `centroid' of a 'heater' or of a heater well is a `centroid' of
its 'cross section' of the heater
or the heater well ¨ i.e. at a specific location. Unless specified otherwise,
this cross section is in the plane
in which a 'heater pattern' (i.e. for heaters and/or heater wells) is defined.
An object or region is "convex" if for every pair of points within the region
or object, every point
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on the straight line segment that joins them is also within the region or
object. A closed curve (e.g. a
perimeter of a two-dimensional region) is 'convex' if the area enclosed by the
closed curve is convex.
A heater 'cross section' may vary along its central axis. Unless specified
otherwise, a heater
'cross section' is the cross section in the plane in which a 'heater pattern'
is defined. Unless specified
otherwise, for a given heater pattern, the 'cross sections' of each of the
heaters are all co-planar.
The term 'displacement' is used interchangeably with 'distance.'
A 'distance' between a location and a heater is the distance between the
location and a `centroid'
of the heater (i.e. a `centroid' of the heater cross section in the plane in
which a 'heater pattern' is
defined). The 'distance between multiple heaters' is the distance between
their centroids.
A "formation" includes one or more hydrocarbon-containing layers, one or more
non-hydrocarbon
layers, an overburden, and/or an underburden. "Hydrocarbon layers" refer to
layers in the formation that
contain hydrocarbons. The hydrocarbon layers may contain non-hydrocarbon
material and hydrocarbon
material. The "overburden" and/or the "underburden" include one or more
different types of
impermeable materials. For example, the overburden and/or underburden may
include rock, shale,
mudstone, or wet/tight carbonate. In some embodiments of in situ heat
treatment processes, the
overburden and/or the underburden may include a hydrocarbon-containing layer
or
hydrocarbon-containing layers that are relatively impermeable and are not
subjected to temperatures
during in situ heat treatment processing that result in significant
characteristic changes of the
hydrocarbon-containing layers of the overburden and/or the underburden. For
example, the underburden
may contain shale or mudstone, but the underburden is not allowed to heat to
pyrolysis temperatures
during the in situ heat treatment process. In some cases, the overburden
and/or the underburden may be
somewhat permeable.
"Formation fluids" refer to fluids present in a formation and may include
pyrolyzation fluid,
synthesis gas, mobilized hydrocarbons, and water (steam). Formation fluids may
include hydrocarbon
fluids as well as non-hydrocarbon fluids. The term "mobilized fluid" refers to
fluids in a
hydrocarbon-containing formation that are able to flow as a result of thermal
treatment of the formation.
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"Produced fluids" refer to fluids removed from the subsurface formation.
A "heat source" is any system for providing heat to at least a portion of a
formation substantially by
conductive and/or radiative heat transfer. For example, a heat source may
include electric heaters such as
an insulated conductor, an elongated member, and/or a conductor disposed in a
conduit. A heat source
may also include systems that generate heat by burning a fuel external to or
in a formation. The systems
may be surface burners, downhole gas burners, flameless distributed
combustors, and natural distributed
combustors. In some embodiments, heat provided to or generated in one or more
heat sources may be
supplied by other sources of energy. The other sources of energy may directly
heat a formation, or the
energy may be applied to a transfer medium that directly or indirectly heats
the formation. It is to be
understood that one or more heat sources that are applying heat to a formation
may use different sources
of energy. Thus, for example, for a given formation some heat sources may
supply heat from electric
resistance heaters, some heat sources may provide heat from combustion, and
some heat sources may
provide heat from one or more other energy sources (for example, chemical
reactions, solar energy, wind
energy, biomass, or other sources of renewable energy). A chemical reaction
may include an exothermic
reaction (for example, an oxidation reaction). A heat source may also include
a heater that provides heat
to a zone proximate and/or surrounding a heating location such as a heater
well.
A "heater" is any system or heat source for generating heat in a well or a
near wellbore region.
Heaters may be, but are not limited to, electric heaters, burners (e.g. gas
burners), pipes through which
hot heat transfer fluid (e.g. molten salt or molten metal) flows, combustors
that react with material in or
produced from a formation, and/or combinations thereof. Unless specified
otherwise, a 'heater'
includes elongate portion having a length that is much greater than cross-
section dimensions. One
example of a 'heater' is a 'molten salt heater' which heats the subsurface
formation primarily by heat
convection between molten salt flowing therein and the subsurface formation.
A 'heater pattern' describes relative locations of heaters in a plane of the
subsurface formation.
"Heavy hydrocarbons" are viscous hydrocarbon fluids. Heavy hydrocarbons may
include highly
viscous hydrocarbon fluids such as heavy oil, tar, and/or asphalt. Heavy
hydrocarbons may include
carbon and hydrogen, as well as smaller concentrations of sulfur, oxygen, and
nitrogen. Additional
elements may also be present in heavy hydrocarbons in trace amounts. Heavy
hydrocarbons may be
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classified by API gravity. Heavy hydrocarbons generally have an API gravity
below about 200. Heavy oil,
for example, generally has an API gravity of about 10-20 , whereas tar
generally has an API gravity
below about 10 . The viscosity of heavy hydrocarbons is generally greater than
about 100 centipoise at
150 C. Heavy hydrocarbons may include aromatics or other complex ring
hydrocarbons.
"Hydrocarbons" are generally defined as molecules formed primarily by carbon
and hydrogen
atoms. Hydrocarbons may also include other elements such as, but not limited
to, halogens, metallic
elements, nitrogen, oxygen, and/or sulfur. Hydrocarbons may be, but are not
limited to, kerogen, bitumen,
pyrobitumen, oils, natural mineral waxes, and asphaltites. Hydrocarbons may be
located in or adjacent to
mineral matrices in the earth. Matrices may include, but are not limited to,
sedimentary rock, sands,
silicilytes, carbonates, diatomites, and other porous media. "Hydrocarbon
fluids" are fluids that include
hydrocarbons. Hydrocarbon fluids may include, entrain, or be entrained in non-
hydrocarbon fluids such
as hydrogen, nitrogen, carbon monoxide, carbon dioxide, hydrogen sulfide,
water, and ammonia.
An "in situ conversion process" refers to a process of heating a hydrocarbon-
containing formation
from heat sources to raise the temperature of at least a portion of the
formation above a pyrolysis
temperature so that pyrolyzation fluid is produced in the formation.
An "in situ heat treatment process" refers to a process of heating a
hydrocarbon-containing
formation with heat sources to raise the temperature of at least a portion of
the formation above a
temperature that results in mobilized fluid, visbreaking, and/or pyrolysis of
hydrocarbon-containing
material so that mobilized fluids, visbroken fluids, and/or pyrolyzation
fluids are produced in the
formation.
For the present disclosure, an `isoperimeteric quotient' of a closed curve
(e.g. polygon) is a ratio
between: (i) the product of 4n and an area closed by the closed curve; and
(ii) the square of the perimeter
of the closed curve.
"Kerogen" is a solid, insoluble hydrocarbon that has been converted by natural
degradation and
that principally contains carbon, hydrogen, nitrogen, oxygen, and sulfur. Coal
and oil shale are typical
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examples of materials that contain kerogen. "Bitumen" is a non-crystalline
solid or viscous hydrocarbon
material that is substantially soluble in carbon disulfide. "Oil" is a fluid
containing a mixture of
condensable hydrocarbons.
5
When an inner zone heater or a point on inner zone perimeter is 'located away'
from a perimeter of
an outer zone, this means that the 'located away' inner zone heater (or the
'located away inner zone
perimeter point') is displaced from the outer zone perimeter by at least a
threshold distance. Unless
otherwise specified, this 'threshold difference' is at least one half of an
inner zone average heater
10 spacing.
"Production" of a hydrocarbon fluid refers to thermally generating the
hydrocarbon fluid (e.g. from
kerogen or bitumen) and removing the fluid from the sub-surface formation via
a production well.
"Pyrolysis" is the breaking of chemical bonds due to the application of heat.
For example, pyrolysis
15 may include transforming a compound into one or more other
substances by heat alone. Heat may be
transferred to a section of the formation to cause pyrolysis.
"Pyrolyzation fluids" or "pyrolysis products" refers to fluid produced
substantially during
pyrolysis of hydrocarbons. Fluid produced by pyrolysis reactions may mix with
other fluids in a
20 formation. The mixture would be considered pyrolyzation fluid or
pyrolyzation product. As used herein,
"pyrolysis zone" refers to a volume of a formation (for example, a relatively
permeable formation such as
a tar sands formation) that is reacted or reacting to form a pyrolyzation
fluid.
25
Unless specified otherwise, when a first quantity QUANTi
'significantly exceeds' a second
quantity QUANT2, a ratio between (i) the greater of the two quantities
MAX(QUANTi, QUANT2) and (ii)
the lesser of the two quantities MIN(QUANTi, QUANT2) is at least 1.5. In some
embodiments, this ratio
is at least 1.7 or at least 1.9.
Unless specified otherwise, a 'significant majority' refers to at least 75%.
In some embodiments,
the significant majority may be at least 80% or at least 85% or at least 90%.
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26
"Superposition of heat" refers to providing heat from two or more heat sources
to a selected section
of a formation such that the temperature of the formation at least at one
location between the heat sources
is influenced by the heat sources.
"Tar" is a viscous hydrocarbon that generally has a viscosity greater than
about 10,000 centipoise
at 15 C. The specific gravity of tar generally is greater than 1.000. Tar may
have an API gravity less than
.
10
A "tar sands formation" is a formation in which hydrocarbons are
predominantly present in the
form of heavy hydrocarbons and/or tar entrained in a mineral grain framework
or other host lithology
(for example, sand or carbonate). Examples of tar sands formations include
formations such as the
Athabasca formation, the Grosmont formation, and the Peace River formation,
all three in Alberta,
Canada; and the Faja a formation in the Orinoco belt in Venezuela.
"Thermally conductive fluid" includes fluid that has a higher thermal
conductivity than air at
standard temperature and pressure (STP) (0 and 101.325 kPa).
"Thermal conductivity" is a property of a material that describes the rate at
which heat flows, in
steady state, between two surfaces of the material for a given temperature
difference between the two
surfaces.
"Thickness" of a layer refers to the thickness of a cross section of the
layer, wherein the cross
section is normal to a face of the layer.
A "U-shaped wellbore" refers to a wellbore that extends from a first opening
in the formation,
through at least a portion of the formation, and out through a second opening
in the formation. In this
context, the wellbore may be only roughly in the shape of a "V" or "U", with
the understanding that the
"legs" of the "U" do not need to be parallel to each other, or perpendicular
to the "bottom" of the "U" for
the wellbore to be considered "U-shaped".
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"Upgrade" refers to increasing the quality of hydrocarbons. For example,
upgrading heavy
hydrocarbons may result in an increase in the API gravity of the heavy
hydrocarbons.
"Visbreaking" refers to the untangling of molecules in fluid during heat
treatment and/or to the
breaking of large molecules into smaller molecules during heat treatment,
which results in a reduction of
the viscosity of the fluid.
"Viscosity" refers to kinematic viscosity at 400 unless otherwise specified.
Viscosity is as
determined by ASTM Method D445.
"VGO" or "vacuum gas oil" refers to hydrocarbons with a boiling range
distribution between 3430 and
538 at 0.101 MPa. VG0 content is determined by ASTM Method D5307.
The term "wellbore" refers to a hole in a formation made by drilling or
insertion of a conduit into
the formation. A wellbore may have a substantially circular cross section, or
another cross-sectional
shape. As used herein, the terms "well" and "opening," when referring to an
opening in the formation
may be used interchangeably with the term "wellbore."
A formation may be treated in various ways to produce many different products.
Different stages or
processes may be used to treat the formation during an in situ heat treatment
process. In some
embodiments, one or more sections of the formation are solution mined to
remove soluble minerals from
the sections. Solution mining minerals may be performed before, during, and/or
after the in situ heat
treatment process. In some embodiments, the average temperature of one or more
sections being solution
mined may be maintained below about 120 C.
In some embodiments, one or more sections of the formation are heated to
remove water from the
sections and/or to remove methane and other volatile hydrocarbons from the
sections. In some
embodiments, the average temperature may be raised from ambient temperature to
temperatures below
about 2200 during removal of water and volatile hydrocarbons.
In some embodiments, one or more sections of the formation are heated to
temperatures that allow
for movement and/or visbreaking of hydrocarbons in the formation. In some
embodiments, the average
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temperature of one or more sections of the formation are raised to
mobilization temperatures of
hydrocarbons in the sections (for example, to temperatures ranging from 1000
to 2500, from 1200 to 2400
,
or from 150 to 230 ).
In some embodiments, one or more sections are heated to temperatures that
allow for pyrolysis
reactions in the formation. In some embodiments, the average temperature of
one or more sections of the
formation may be raised to pyrolysis temperatures of hydrocarbons in the
sections (for example,
temperatures ranging from 230 to 900 , from 240 to 400 or from 250 to 350
).
Heating the hydrocarbon-containing formation with a plurality of heat sources
may establish
thermal gradients around the heat sources that raise the temperature of
hydrocarbons in the formation to
desired temperatures at desired heating rates. The rate of temperature
increase through mobilization
temperature range and/or pyrolysis temperature range for desired products may
affect the quality and
quantity of the formation fluids produced from the hydrocarbon-containing
formation. Slowly raising the
temperature of the formation through the mobilization temperature range and/or
pyrolysis temperature
range may allow for the production of high quality, high API gravity
hydrocarbons from the formation.
Slowly raising the temperature of the formation through the mobilization
temperature range and/or
pyrolysis temperature range may allow for the removal of a large amount of the
hydrocarbons present in
the formation as hydrocarbon product.
In some in situ heat treatment embodiments, a portion of the formation is
heated to a desired
temperature instead of slowly heating the temperature through a temperature
range. In some
embodiments, the desired temperature is 3000, 3250, or 3500 Other temperatures
may be selected as the
desired temperature.
Superposition of heat from heat sources allows the desired temperature to be
relatively quickly and
efficiently established in the formation. Energy input into the formation from
the heat sources may be
adjusted to maintain the temperature in the formation substantially at a
desired temperature.
Mobilization and/or pyrolysis products may be produced from the formation
through production
wells. In some embodiments, the average temperature of one or more sections is
raised to mobilization
temperatures and hydrocarbons are produced from the production wells. The
average temperature of one
or more of the sections may be raised to pyrolysis temperatures after
production due to mobilization
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decreases below a selected value. In some embodiments, the average temperature
of one or more sections
may be raised to pyrolysis temperatures without significant production before
reaching pyrolysis
temperatures. Formation fluids including pyrolysis products may be produced
through the production
wells.
In some embodiments, the average temperature of one or more sections may be
raised to
temperatures sufficient to allow synthesis gas production after mobilization
and/or pyrolysis. In some
embodiments, hydrocarbons may be raised to temperatures sufficient to allow
synthesis gas production
without significant production before reaching the temperatures sufficient to
allow synthesis gas
production. For example, synthesis gas may be produced in a temperature range
from about 4000 to about
1200 , about 500 to about 11000, or about 550 to about 1000 A synthesis gas
generating fluid (for
example, steam and/or water) may be introduced into the sections to generate
synthesis gas. Synthesis
gas may be produced from production wells.
Solution mining, removal of volatile hydrocarbons and water, mobilizing
hydrocarbons,
pyrolyzing hydrocarbons, generating synthesis gas, and/or other processes may
be performed during the
in situ heat treatment process. In some embodiments, some processes may be
performed after the in situ
heat treatment process. Such processes may include, but are not limited to,
recovering heat from treated
sections, storing fluids (for example, water and/or hydrocarbons) in
previously treated sections, and/or
sequestering carbon dioxide in previously treated sections.
FIG. 1 depicts a schematic view of an embodiment of a portion of the in situ
heat treatment system
for treating the hydrocarbon-containing formation. The in situ heat treatment
system may include barrier
wells 1200. Barrier wells are used to form a barrier around a treatment area.
The barrier inhibits fluid
flow into and/or out of the treatment area. Barrier wells include, but are not
limited to, dewatering wells,
vacuum wells, capture wells, injection wells, grout wells, freeze wells, or
combinations thereof. In some
embodiments, barrier wells 1200 are dewatering wells. Dewatering wells may
remove liquid water
and/or inhibit liquid water from entering a portion of the formation to be
heated, or to the formation being
heated. In the embodiment depicted in FIG. 1, the barrier wells 1200 are shown
extending only along one
side of heater sources 1202, but the barrier wells typically encircle all heat
sources 1202 used, or to be
used, to heat a treatment area of the formation.
Heat sources 1202 are placed in at least a portion of the formation. Heat
sources 1202 may include
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heaters such as insulated conductors, conductor-in-conduit heaters, surface
burners, flameless distributed
combustors, and/or natural distributed combustors. Heat sources 1202 may also
include other types of
heaters. Heat sources 1202 provide heat to at least a portion of the formation
to heat hydrocarbons in the
formation. Energy may be supplied to heat sources 1202 through supply lines
1204. Supply lines 1204
5 may be structurally different depending on the type of heat source or
heat sources used to heat the
formation. Supply lines 1204 for heat sources may transmit electricity for
electric heaters, may transport
fuel for combustors, or may transport heat exchange fluid that is circulated
in the formation. In some
embodiments, electricity for an in situ heat treatment process may be provided
by a nuclear power plant
or nuclear power plants. The use of nuclear power may allow for reduction or
elimination of carbon
10 dioxide emissions from the in situ heat treatment process.
When the formation is heated, the heat input into the formation may cause
expansion of the
formation and geomechanical motion. The heat sources may be turned on before,
at the same time, or
during a dewatering process. Computer simulations may model formation response
to heating. The
15 computer simulations may be used to develop a pattern and time sequence
for activating heat sources in
the formation so that geomechanical motion of the formation does not adversely
affect the functionality
of heat sources, production wells, and other equipment in the formation.
Heating the formation may cause an increase in permeability and/or porosity of
the formation.
20 Increases in permeability and/or porosity may result from a reduction of
mass in the formation due to
vaporization and removal of water, removal of hydrocarbons, and/or creation of
fractures. Fluid may
flow more easily in the heated portion of the formation because of the
increased permeability and/or
porosity of the formation. Fluid in the heated portion of the formation may
move a considerable distance
through the formation because of the increased permeability and/or porosity.
The considerable distance
25 may be over 1000 m depending on various factors, such as permeability of
the formation, properties of
the fluid, temperature of the formation, and pressure gradient allowing
movement of the fluid. The ability
of fluid to travel considerable distance in the formation allows production
wells 1206 to be spaced
relatively far apart in the formation.
30 Production wells 1206 are used to remove formation fluid from the
formation. In some
embodiments, production well 1206 includes a heat source. The heat source in
the production well may
heat one or more portions of the formation at or near the production well. In
some in situ heat treatment
process embodiments, the amount of heat supplied to the formation from the
production well per meter of
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the production well is less than the amount of heat applied to the formation
from a heat source that heats
the formation per meter of the heat source. Heat applied to the formation from
the production well may
increase formation permeability adjacent to the production well by vaporizing
and removing liquid phase
fluid adjacent to the production well and/or by increasing the permeability of
the formation adjacent to
the production well by formation of macro and/or micro fractures.
More than one heat source may be positioned in the production well. A heat
source in a lower
portion of the production well may be turned off when superposition of heat
from adjacent heat sources
heats the formation sufficiently to counteract benefits provided by heating
the formation with the
production well. In some embodiments, the heat source in an upper portion of
the production well may
remain on after the heat source in the lower portion of the production well is
deactivated. The heat source
in the upper portion of the well may inhibit condensation and reflux of
formation fluid.
In some embodiments, the heat source in production well 1206 allows for vapor
phase removal of
formation fluids from the formation. Providing heating at or through the
production well may: (1) inhibit
condensation and/or refluxing of production fluid when such production fluid
is moving in the
production well proximate the overburden, (2) increase heat input into the
formation, (3) increase
production rate from the production well as compared to a production well
without a heat source, (4)
inhibit condensation of high carbon number compounds (C6 hydrocarbons and
above) in the production
well, and/or (5) increase formation permeability at or proximate the
production well.
Subsurface pressure in the formation may correspond to the fluid pressure
generated in the
formation. As temperatures in the heated portion of the formation increase,
the pressure in the heated
portion may increase as a result of thermal expansion of in situ fluids,
increased fluid generation and
vaporization of water. Controlling rate of fluid removal from the formation
may allow for control of
pressure in the formation. Pressure in the formation may be determined at a
number of different locations,
such as near or at production wells, near or at heat sources, or at monitor
wells.
In some hydrocarbon-containing formations, production of hydrocarbons from the
formation is
inhibited until at least some hydrocarbons in the formation have been
mobilized and/or pyrolyzed.
Formation fluid may be produced from the formation when the formation fluid is
of a selected quality. In
some embodiments, the selected quality includes an API gravity of at least
about 20 , 30 , or 40 .
Inhibiting production until at least some hydrocarbons are mobilized and/or
pyrolyzed may increase
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conversion of heavy hydrocarbons to light hydrocarbons. Inhibiting initial
production may minimize the
production of heavy hydrocarbons from the formation. Production of substantial
amounts of heavy
hydrocarbons may require expensive equipment and/or reduce the life of
production equipment.
In some hydrocarbon-containing formations, hydrocarbons in the formation may
be heated to
mobilization and/or pyrolysis temperatures before substantial permeability has
been generated in the
heated portion of the formation. An initial lack of permeability may inhibit
the transport of generated
fluids to production wells 1206. During initial heating, fluid pressure in the
formation may increase
proximate heat sources 1202. The increased fluid pressure may be released,
monitored, altered, and/or
controlled through one or more heat sources 1202. For example, selected heat
sources 1202 or separate
pressure relief wells may include pressure relief valves that allow for
removal of some fluid from the
formation.
In some embodiments, pressure generated by expansion of mobilized fluids,
pyrolysis fluids or
other fluids generated in the formation may be allowed to increase although an
open path to production
wells 1206 or any other pressure sink may not yet exist in the formation. The
fluid pressure may be
allowed to increase towards a litho static pressure. Fractures in the
hydrocarbon-containing formation
may form when the fluid approaches the lithostatic pressure. For example,
fractures may form from heat
sources 1202 to production wells 1206 in the heated portion of the formation.
The generation of fractures
in the heated portion may relieve some of the pressure in the portion.
Pressure in the formation may have
to be maintained below a selected pressure to inhibit unwanted production,
fracturing of the overburden
or underburden, and/or coking of hydrocarbons in the formation.
After mobilization and/or pyrolysis temperatures are reached and production
from the formation is
allowed, pressure in the formation may be varied to alter and/or control a
composition of formation fluid
produced, to control a percentage of condensable fluid as compared to non-
condensable fluid in the
formation fluid, and/or to control an API gravity of formation fluid being
produced. For example,
decreasing pressure may result in production of a larger condensable fluid
component. The condensable
fluid component may contain a larger percentage of olefins.
In some in situ heat treatment process embodiments, pressure in the formation
may be maintained
high enough to promote production of formation fluid with an API gravity of
greater than 20 .
Maintaining increased pressure in the formation may inhibit formation
subsidence during in situ heat
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treatment. Maintaining increased pressure may reduce or eliminate the need to
compress formation fluids
at the surface to transport the fluids in collection conduits to treatment
facilities.
Maintaining increased pressure in a heated portion of the formation may
surprisingly allow for
production of large quantities of hydrocarbons of increased quality and of
relatively low molecular
weight. Pressure may be maintained so that formation fluid produced has a
minimal amount of
compounds above a selected carbon number. The selected carbon number may be at
most 25, at most 20,
at most 12, or at most 8. Some high carbon number compounds may be entrained
in vapor in the
formation and may be removed from the formation with the vapor. Maintaining
increased pressure in the
formation may inhibit entrainment of high carbon number compounds and/or multi-
ring hydrocarbon
compounds in the vapor. High carbon number compounds and/or multi-ring
hydrocarbon compounds
may remain in a liquid phase in the formation for significant time periods.
The significant time periods
may provide sufficient time for the compounds to pyrolyze to form lower carbon
number compounds.
Generation of relatively low molecular weight hydrocarbons is believed to be
due, in part, to
autogenous generation and reaction of hydrogen in a portion of the hydrocarbon-
containing formation.
For example, maintaining an increased pressure may force hydrogen generated
during pyrolysis into the
liquid phase within the formation. Heating the portion to a temperature in a
pyrolysis temperature range
may pyrolyze hydrocarbons in the formation to generate liquid phase
pyrolyzation fluids. The generated
liquid phase pyrolyzation fluids components may include double bonds and/or
radicals. Hydrogen (H2)
in the liquid phase may reduce double bonds of the generated pyrolyzation
fluids, thereby reducing a
potential for polymerization or formation of long chain compounds from the
generated pyrolyzation
fluids. In addition, H2 may also neutralize radicals in the generated
pyrolyzation fluids. H2 in the liquid
phase may inhibit the generated pyrolyzation fluids from reacting with each
other and/or with other
compounds in the formation.
Formation fluid produced from production wells 1206 may be transported through
collection
piping 1208 to treatment facilities 1210. Formation fluids may also be
produced from heat sources 1202.
For example, fluid may be produced from heat sources 1202 to control pressure
in the formation adjacent
to the heat sources. Fluid produced from heat sources 1202 may be transported
through tubing or piping
to collection piping 1208 or the produced fluid may be transported through
tubing or piping directly to
treatment facilities 1210. Treatment facilities 1210 may include separation
units, reaction units,
upgrading units, fuel cells, turbines, storage vessels, and/or other systems
and units for processing
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produced formation fluids. The treatment facilities may form transportation
fuel from at least a portion of
the hydrocarbons produced from the formation. In some embodiments, the
transportation fuel may be jet
fuel, such as JP-8.
Formation fluid may be hot when produced from the formation through the
production wells. Hot
formation fluid may be produced during solution mining processes and/or during
in situ heat treatment
processes. In some embodiments, electricity may be generated using the heat of
the fluid produced from
the formation. Also, heat recovered from the formation after the in situ
process may be used to generate
electricity. The generated electricity may be used to supply power to the in
situ heat treatment process.
For example, the electricity may be used to power heaters, or to power a
refrigeration system for forming
or maintaining a low temperature barrier. Electricity may be generated using a
Kalina cycle, Rankine
cycle or other thermodynamic cycle. In some embodiments, the working fluid for
the cycle used to
generate electricity is aqua ammonia.
FIGS. 2A-2E illustrate a pattern of heaters 220 within a cross section (e.g. a
horizontal or vertical
or slanted cross section) of a hydrocarbon-bearing subsurface formation such
as oil shale, tar sands, coals,
bitumen-containing carbonates, gibsonite, or heavy oil - containing
diatomite). In some embodiments,
each of the heaters (e.g. within heater wells) includes an elongate section
having an elongate/central axis
locally perpendicular to the cross section of the subsurface formation. Each
dot 220 in FIGS. 2A-2D
represents a location of a cross section of the respective elongate heater in
the plane defined by the
subsurface cross section. The heater spatial pattern of FIGS. 2A-2D, or the
heater pattern of any other
embodiment, may occur at any depth within the subsurface formation, for
example, at least 50 meters or
at least 100 meters or at least 150 meters or at least 250 meters beneath the
surface, or more.
In the example of FIGS. 2A-2E, heaters 220 are respectively disposed at
relatively high and low
spatial densities (and relatively short and long heater spacings) within
nested inner 210 and outer 214
zones of the cross section of the hydrocarbon-bearing formation. In the
particular example of FIGS.
2A-2D, (i) nineteen inner zone heaters 226 are disposed at a relatively high
density (and relatively short
spacings between neighboring heaters) both within an inner zone 210 and around
a perimeter 204 of the
inner zone 210 (i.e. referred to as an 'inner perimeter'), and (ii) twelve
outer zone 228 heaters are
arranged a relatively low density (and relatively long spacings between
neighboring heaters) in outer
zone 214 so as to be distributed around a perimeter 208 of outer zone 214. In
the non-limiting example
of FIG. 2A-2E, within outer zone 214, (i) all outer zone heaters are
distributed around the perimeter 208
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of outer zone 214, and (ii) the region between the inner 204 and outer 208
perimeters is relatively free of
heaters.
Because heater patterns are defined within a two-dimensional cross-section of
the subsurface
5
formation, the terms 'inner zone' 210 and 'outer zone' 214 refer to
portions of the two-dimensional cross
section of the subsurface formation. Because heater patterns are defined
within a two-dimensional
cross-section of the subsurface formation, various spatial properties related
to heater location such as
heater spacing, density, and 'distance to heater' are also defined within a
two-dimensional planar
cross-section of the formation.
For the present disclosure, the 'inner zone' 210 refers to the entire area
enclosed by a perimeter 204
thereof. The 'outer zone' 214 refers to the entire area, (i) outside of inner
zone 210 that is (ii) enclosed by
a perimeter 208 outer zone 214.
As will be discussed below, in some embodiments, the heater patterns
illustrated in the
non-limiting example of FIGS. 2A-2E, and in other embodiments disclosed
herein, are useful for
minimizing and/or substantially minimizing a number of heaters 220 required to
rapidly reach a
relatively-sustained substantially steady-state production rate of hydrocarbon
fluids in the subsurface
formation.
In some embodiments, during an initial phase of heater operation, the
subsurface formation within
the smaller inner zone 210 heats up relatively quickly, due to the high
spatial density and short spacing of
heaters therein. This high heater spatial density may expedite production of
hydrocarbons within inner
zone 210 during an earlier phase of production when the average temperature in
the inner zone 210
exceeds (e.g. significantly exceeds) that of the outer zone 214. During a
later phase of operation, the
combination of (i) heat provided by outer zone heaters; and (ii) outward flow
of thermal energy from
inner zone 210 to outer zone 214 may heat the outer zone 214.
As will be discussed below (see, for example, FIGS. 4-7), in some embodiments
two distinct
'production peaks' may be observed ¨ an earlier inner zone production peak 310
and a later outer zone
production peak 330. In some embodiments, these production peaks collectively
contribute to an
'overall' hydrocarbon production rate within the 'combined' region (i.e. the
combination of inner 210
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and outer 214 regions) that (i) ramps up relatively quickly due to the inner
zone peak (i.e. has a 'fast rise
time') and (ii) is sustained at a near-steady rate for an extended period of
time.
For the present disclosure, 'inner zone perimeter 204' or 'inner perimeter
204' which forms a
boundary between inner 210 and outer 214 zones, is considered part of inner
zone 210. In the example of
FIGS. 2A-2E the twelve heaters located on the 'inner hexagon' 204 are inner
zone heaters 226. The
'outer zone perimeter 208' or 'outer perimeter 208' which forms a boundary
between the outer zone 214
and 'external locations' outside of the outer zone is considered part of outer
zone 214. The terms 'inner
zone perimeter 204' and 'inner perimeter 204' are used interchangeably and
have the same meaning; the
terms 'outer zone perimeter 208' and 'outer perimeter 208' are used
interchangeably and have the same
meaning.
As illustrated in FIG. 2B, inner 210 and outer 214 zones are (i) nested so
that outer zone 214
surrounds inner zone 210, (ii) share a common centroid location 298, and (iii)
have like-shaped
perimeters 204, 208. In the example of FIGS. 2A-2E, inner 204 and outer 208
zone perimeters are both
regular hexagons. In the non-limiting example of FIGS.2A-2E, inner zone
heaters are 226 dispersed
throughout the inner zone at exactly a uniform spacing s. In the example if
FIGS. 2A-2E, inner zone
heaters 226 are uniformly arranged on an equilateral triangular grid
throughout the inner zone 210 ¨ a
length of each triangle side is s.
Within outer zone 214, an 'average heater spacing' is approximately double
that of the inner zone.
Along outer perimeter 208, heaters are distanced from each other by 2s. For
every pair of adjacent
heaters situated on outer perimeter 208, a third heater on inner perimeter 206
is distanced from both
heaters of the pair of adjacent heaters by 2s.
.
In the example of FIGS. 2A-2E, twelve outer zone heaters are uniformly
distributed around regular
hexagonally-shaped outer perimeter 208 so that adjacent heaters on outer
perimeter 208 (i) are separated
by a separation distance 2s; and (ii) subtend an angle equal to 30 degrees
relative to the center 298 of
outer zone.
An area enclosed by inner perimeter 204 (i.e. an area of inner zone 210) is
equal to 64Jis 2 while an
area enclosed by outer perimeter 208 (i.e. an area of the 'combined area' that
is the sum of inner 210 and
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outer 214 zones) is equal to 24lis 2 or four times the area enclosed by the
inner perimeter 204. An area
ratio between areas of the outer 210 and inner 214 zones is three.
The heater spatial density in inner zone 210 significantly exceeds that within
outer zone 214. As
will be discussed below with reference to FIG. 30, according to a 'reservoir
engineering' definition of
heater spatial density, the density within inner zone 210 of FIGS. 2A-2E is
three times that of outer zone
214.
For the example of FIG. 2A-2E, the heater pattern includes a total of 31
heaters. If the heaters were
all drilled at the average inner zone 210 spacing, a total of 61 heaters would
be required. Compared to
drilling all of the heaters at an average spacing within inner zone 210, the
pattern of FIGS. 2A-2E
requires only about half as many heaters.
In the example of FIGS. 2A-2E the inner zone and outer zone perimeters 204,
208 are both
regularly-hexagonally shaped. In some embodiments, the shapes of the inner
and/or outer zone
perimeters 204, 208 (and consequently the shape of the inner 210 and/or outer
214 zones) are defined by
the locations of the heaters themselves ¨ for example, the heater locations
may define vertex locations for
a polygon-shaped perimeter.
For example, in some embodiments, inner zone 210 may be defined by a 'cluster'
of heaters in a
relatively high-spatial-density region surrounded by a region where the
density of heaters is significantly
lower. In these embodiments, the edge of this cluster of heaters where an
observable 'density drop' may
define the border (i.e. inner zone perimeter 204) between (i) the inner zone
210 where heaters are
arranged in a 'cluster' at a relatively high density and (ii) the outer zone
214.
In some embodiments, the perimeter of outer zone 208 may be defined by a
'ring' (i.e. not
necessarily circularly-shaped) of heaters outside of inner zone 210
distributed around a centroid of outer
zone 214. This ring may be relatively 'thin' compared to the cluster of
heaters that form the inner zone
210. Overall, a local density within this 'ring' of heaters defining outer
zone perimeter 208 is relatively
high compared to locations adjacent to the ring ¨ i.e. locations within outer
zone 214 (i.e. 'internal
locations' within outer zone 214 away from inner-zone 204 and outer-zone 208
perimeters) and outside
of outer zone 214.
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Alternatively or additionally, the inner and/or outer zone perimeters 204, 208
are polygon shaped
and are defined such that heaters (i.e. a centroid thereof in a cross-section
of the subsurface where the
heater pattern is defined) are located at all polygon vertices of perimeters
204, 208. As noted elsewhere,
any heater pattern disclosed herein may also be a heater well pattern. As
such, the perimeters 204, 208
may be defined such that heater well centroids i.e. in a cross-section of the
subsurface where the heater
pattern is defined) are located at all polygon vertices of perimeters 204,
208.
Reference is now made to FIG. 2C. As illustrated in FIG. 2C, heaters are
labeled (i.e. for the
non-limiting example of FIGS. 2A-2E) as inner zone heaters 226 or outer zone
heaters 228. In the
example of FIGS. 2A-2E, 19 heaters are inner zone heaters 226 and 12 heaters
are outer zone heaters 228.
As illustrated in FIG. 2C, heaters may be labeled (i.e. for the non-limiting
example of FIGS. 2A-2D) as (i)
'interior of inner zone heaters' 230 located in an 'interior region' of the
inner zone 210 away from the
inner zone perimeter; (ii) inner perimeter heaters 232; (iii) interior of
outer zone heaters' 234 located in
an 'interior region' of the inner zone 210 away from the inner zone perimeter;
and (iv) outer perimeter
heaters 236. In the example of FIG. 2C, there are seven 'interior of inner
zone heaters' 230, twelve inner
perimeter heaters 232, zero interior of outer zone heaters' 234, and twelve
outer perimeter heaters 236.
In the example of FIGS. 2A-2E and FIG. 3, inner 210 and outer 214 zones are
like-shaped and
shaped as regular hexagons.
Some features disclosed herein may be defined relative to a 'characteristic
length' within inner
210 or outer 214 zones. For the present disclosure, a 'characteristic length'
within a region of a
cross-section of the subsurface formation is a square root of an area of the
region. Thus, a 'characteristic
inner zone length' is a square root of an area of inner zone 210, and a
'characteristic inner zone length' is
a square root of an area of outer zone 214. For the 'regular hexagon' example
of FIGS. 2-3, (i) the area of
inner zone 210 is 6-Nis 2 so that the 'characteristic inner zone length' is
approximately 3.2s; (ii) an area
of outer zone 214 is three times that of inner zone 210 so that the
'characteristic outer zone length' is
approximately 5.6s.
It is appreciated that heaters are typically within heater wells (e.g. having
elongate sections), any
heater spatial pattern (and any feature or combination of feature(s))
disclosed herein may also be a heater
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well pattern.
One salient feature of the pattern/arrangement of FIG. 2D is the presence of
production wells both
within inner 210 and outer 214 zones.
In various embodiments, some or all (i.e. any combination of) the following
features related to
'heater patterns' may be observed:
(A) A heater spatial density, within the inner zone 210 significantly exceeds
that of the outer zone
214 and/or an 'average spacing between neighboring heaters' within the outer
zone 214 significantly
exceeds that of the inner zone 210 and/or within outer zone 214, an average
distance to a nearest heater
significantly exceeds that of inner zone 210. As will be discussed below with
reference to FIGS. 4-7, in
some embodiments, heater patterns providing this feature may be useful for
expediting a rate of
conversion of kerogen and/or bitumen of the hydrocarbon-bearing formation into
hydrocarbon fluids
within inner zone 210 so that an inner zone production peak 310 occurs in an
earlier stage of production,
and an outer zone production peak 330 only occurs after a delay.
(B) Inner zone heaters 226 and outer zone heaters 228 are distributed 'around'
respective centroids
298, 296 of inner 210 and outer 214 zones. As will be discussed below (see
FIGS. 26A-26B), when
heaters are distributed 'around' a centroid then for every orientation of a
'reference ray' starting at an
'origin' at the location of the centroid (296 or 298), at least one heater is
located (i.e. the heater cross
section centroid is located) in every quadrant (i.e. every 90 degree sector)
defined by the origin/centroid
(296 or 298). In different embodiments, heaters are arranged within inner 210
and/or outer 214 zones so
that inner zone heaters 226 or outer zone heaters 228 are present on every 72
degree sector or on every 60
degree sector or on every 45 degree sector of inner or outer zones for every
reference ray orientation.
(C) Outer zone heaters 228 are predominantly located on or near the outer zone
perimeter 208. In
some embodiments, the relatively high density of heaters in inner zone 210
causes an outward flow of
thermal energy from inner zone 210 into outer zone 214. Arrangement of outer
zone heaters 228 so that
they are predominantly located on or near the outer zone perimeter 208 may
facilitate the 'inward flow'
of thermal energy so as to at least partly 'balance' the outward flow of
thermal energy into outer zone 214
from inner zone 210.
In some embodiments where heaters are deployed at most sparsely in the
interior portion of outer
zone 210 away from inner and outer zone perimeters 204, 208. This may be
useful for reducing a number
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of heaters required to produce hydrocarbon fluids in a required manner..
Furthermore, the relative lack of
heaters within the 'middle portion' of outer zone 210 (i.e. distanced from
both perimeters 204, 208) may
delay production of fluids from this middle portion of outer zone 210 and
within outer zone 210 as a
whole. As will be discussed below, with reference to FIGS. 4-7, this delay may
be useful for producing
5 hydrocarbon fluids in a manner where a significant production rate (e.g.
at least half of a maximum
production rate) is sustained for a relatively extended period of time.
(D) A ratio between areas enclosed by the outer 208 and inner 204 perimeters
is at least 3 or at least
3.5 and/or at most 10 or at most 9 or at most 8 or at most 7 or at most 6 or
at most 5 or at most 4.5 and/or
10 about 4. In the examples of FIGS. 2-4 and 7-9, this ratio is exactly
four. In some embodiments, arranging
heaters according to any of these ratios may be useful for producing
hydrocarbons so that an overall rate
of production ramps up relatively rapidly (i.e. short rise time) while is
sustained for a relatively extended
period of time. In some embodiment, if this ratio is too small, then the
amount of time that the rate of
production is sustained may be too short and/or the thermal efficiency of the
heater pattern may be
15 reduced due to a reduction in the re-use of thermal energy from inner
zone heaters within outer zone 210.
If this ratio is too large, this may, for example, cause a dip in production
after hydrocarbon fluids are
rapidly produced within inner zone 210.
(E) The centroid 296 of inner zone 210 is located in a central portion of the
region enclosed by
20 outer zone perimeter 208 ¨ upon visual inspection of the heater patterns
of FIGS. 2-11, it is clear that this
is true for all of these heater patterns. In some embodiments, substantially
centering the inner zone
within outer zone is useful for ensuring that a higher fraction of thermal
energy from heaters 226 within
inner zone 210 is re-used within outer zone 214, thus increasing the overall
thermal efficiency of the
heater pattern. Unless specified otherwise, when centroid 296 of inner zone
210 is located in a central
25 portion of the region enclosed by outer zone perimeter 208, centroid 296
of inner zone 210 is in the inner
third of a region enclosed by outer zone perimeter 208. In some embodiments,
centroid 296 of inner zone
210 is in the inner quarter or inner fifth or inner sixth or inner tenth.
(F) In the example of FIGS. 2-11, there is no contact between perimeters 204,
208 of inner 210 and
30 outer zones 214. In some embodiments, at least 30% or at least a
majority of inner zone perimeter 204 is
located away from outer zone perimeter 214. In some embodiments, at least a
majority or at least a
significant majority (i.e. at least 75%) of the inner zone heaters are located
away from the outer zone
perimeter 208.
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When an inner zone heater or a point on inner zone perimeter 204 is located
away from a perimeter
208 of outer zone 214, this means that the located away inner zone heater (or
the located away point on
inner zone perimeter 204) is displaced from the outer zone perimeter 208 by at
least a threshold distance.
Unless otherwise specified, this threshold distance is at least one half of an
inner zone average heater
spacing.
Alternatively or additionally, in some embodiments, this threshold distance is
at least: (i) at least
two-thirds of the inner zone average heater spacing and/or (ii) at least the
inner zone average heater
spacing or (iii) at least an average distance within inner zone (i.e. averaged
over all locations within inner
zone 210) to a nearest heater; and/or (ii) at least three times (or at least
four times or at least five times)
the square root of the area of the inner zone divided the number of inner zone
heaters. In the example of
FIGS. 2-3, the square root of the area of the inner zone is 3.2s and the
number of inner zone heaters is 19,
so four times the square root of the area of the inner zone is about 0.51s. In
the example of FIG. 4, the
square root of the area of the inner zone is 3.8s and the number of inner zone
heaters is 25, so four times
the square root of the area of the inner zone is about 0.44s.
(G) Perimeters 204, 208 of inner 210 and/or outer 214 zones are convex or
substantially convex ¨
the skilled artisan is directed to the definition of 'substantially convex'
described below with reference to
FIG. 29. In some embodiments, this may be useful for facilitating outward flow
of heat generated by
inner zone heaters located at or near the perimeter 204 of inner zone 210 ¨
e.g. so that heat from inner
zone heaters located at or near inner zone perimeter 204 flows outwards into
outer zone 214 and toward
outer zone perimeter 208 rather than flowing inwards towards a centroid 296 of
inner zone 210. In some
embodiments, this increases the thermal efficiency of the heater pattern. In
some embodiments, a
candidate shape is 'substantially convex' if an area enclosed by a minimally
enclosed convex shape
exceeds the area of the candidate shape by at most 20% or at most 10% or at
most 5%.
For the present disclosure, whenever something (i.e. an area or a closed curve
such as a perimeter
of an area) is described as convex it may, in some embodiments be
'substantially convex.' Whenever
something is described as 'substantially convex' it may, in alternative
embodiments be convex.
(H) An isoperimetric quotient of perimeters 204, 208 of the inner 210 and/or
outer 214 zone is at
least 0.4 or at least about 0.5 or at least 0.6. In the present disclosure, an
`isoperimetric quotient' of a
42-cA
closed curve is defined as the isoperimetric coefficient of the area enclosed
by the closed curve, i.e. ¨p2
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where P is the length of the perimeter of the closed curve, and A is the area
enclosed by the closed curve
(e.g. an area of inner zone 210 for the 'closed curve' defined by perimeter
204 or the sum of the areas of
inner 210 and outer 214 zones for the 'closed curve' defined by perimeter
208).
(I) An 'aspect ratio' of perimeter 204 of inner 210 and/or of perimeter 208 of
outer 214 zone is at
most 5 or at most 4.5 or at most 4 or at most 3.5 or at most 3 or at most 2.5
or at most 2.0 or at most 1.5.
An "aspect ratio" of a shape (i.e. either the shape or an enclosing perimeter
thereof) refers to a ratio
between its longer dimension and its shorter dimension. . In some embodiments,
the inner and outer
zones have a similar and/or relatively low aspect ratio that may be useful for
efficient re-use of
inner-zone-generated thermal energy within outer zone' 214 and/or for
obtaining a production curve
exhibiting a relatively fast rise-time with sustained substantial production
rate.
(J) Perimeters 204, 208 of inner 210 and/or outer 214 zones have common shape
characteristics.
In some embodiments, inner and outer zone perimeters 204, 208 are like-shaped.
This is not a
requirement. In some embodiments, /PONNER is the isoperimeter quotient of
inner zone 210, /PQouTER is
the isoperimeter quotient of outer zone 214, MAX(/PONNER, /PQouTER) is the
greater of /PONNER and
IPQouTER, MIN(IPQINNER, IPQouTER) is the lesser of /PQ/NNER and /PQoUTER, and
a ratio
MAX(IPO
-INNER' IPQOUTER)
\ is at most 3 or at most 2.5 or at most 2 or at most 1.75 or at most 1.5 or
at most
M/M/P0
-INNER ' 113QOUTER i
1.3 or at most 1.2 or at most 1.15 or at most 1.1 or at most 1.05 or exactly
1.
(K) In some embodiments, heaters are 'distributed substantially uniformly' in
inner 210 and/or
outer 214 outer zone. This may allow for more efficient heating of inner zone
210. In some embodiments,
visual inspection of a 'heater layout' diagram describing positions of heater
cross sections is sufficient to
indicate when heaters are 'distributed substantially uniformly' throughout one
or more of the zone(s).
Alternatively or additionally, heaters may be distributed so as to provide a
relatively low 'heater
standard deviation spacing' relative to a 'heater average spacing in one or
more of the zone(s).
Within any area of the subsurface formation (e.g. within inner zone 210 or
outer zone 214), there
are a number of 'neighboring heater spacings' within the area of the formation
¨ for example, in FIG.
22C (i.e. there are 36 spacings in outer zone 214 (i.e. 30 of the spacings
have values of 2a and 6 of the
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spacings have values of -Nla ) and there are 32 spacings in inner zone 210
(i.e. all 36 of the spacings
have a value of a). In this example, the average spacing in inner zone 210 is
exactly a while the average
spacing in outer zone 214 is 64Ja +30(2a) L- 36
1.95a. It is also possible to compute a 'standard deviation
heater spacing' ¨ in the inner zone 214 this is exactly zero and in the outer
zone the 'standard deviation
heater spacing'
is
.\160a ¨1.954 +30(2a ¨1.9502 116(0.048a2)+30(0.0025a2) 110.363a2
¨ 0.1a . In the example
36 36 36
of FIG. 22C, a quotient of the standard deviation spacing and the average
spacing is about 0.05.
In the example of FIGS. 5A and 24A, the average spacing is 17-&+18aL- 1.87a.
In the
example of FIGS. 5A and 25A, the 'standard deviation heater spacing' is
170a ¨1.874 +18(2a ¨1.8702 1117(0.0196a2)+18(0.0169a2)
L- 0.135a, and a quotient of the
35 36
standard deviation spacing and the average spacing is about 0.072.
In different embodiments, a quotient between a standard deviation spacing and
an average
spacing is at most 0.5 or at most 0.4 or at most 0.3 or at most 0.2 or at most
0.1.
(L) In some embodiments, heaters are dispersed throughout inner zone 214
rather than being
limited to specific locations within inner zone (e.g. perimeter 204) ¨ upon
visual inspection of the heater
patterns of FIGS. 2-3, it is clear that this feature is true for all of these
heater patterns. In some
embodiments, the heaters are distributed according to an average heater
spacing that is 'small' compared
to some 'characteristic length' of inner zone 210 ¨ for example, an average
heater spacing within inner
zone 210 may be at most one-half or at most two-fifths or at most one-third or
at most one-quarter of the
square root of an area of inner zone 210. This 'close heater' spacing relative
to a characteristic length of
inner zone 210 may be useful for outwardly directing thermal energy from inner
zone heaters so as to
facilitate heat flow into outer zone 214.
In some embodiments, a ratio between (i) a product of a number of inner zone
heaters 226 and a
square of the average spacing in the inner zone and (ii) an area of inner zone
210 is at least 0.75 or at least
1 or at least 1.25 or at least 1.5.
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In some embodiments, at least 10% or at least 20% or at least 30% or at least
40% or at least 50% of
inner zone heaters are 'interior of inner zone heaters 230' located within
inner zone 210 away from inner
zone perimeter 204;
(M) One or more production wells located in inner 210 and/or outer 214 zones.
In some
embodiments, one or more production wells (e.g. multiple production wells) are
arranged within inner
and/or outer zones to efficiently recovering hydrocarbon fluids from the
subsurface. In some
embodiments, locating production well(s) in inner zone 210 is useful for
quickly removing hydrocarbon
fluids located therein. In some embodiments, it is useful to locate production
wells on different sides of
the inner zone so as to facilitate the fast and/or efficient removal of
hydrocarbon fluids from the
subsurface formation.
When two inner zone production wells having respective locations
LOCpRop_wELLizi and
LOCpRop_wELL/z2 are 'are on different sides' of inner zone 210 having centroid
CENTIz 298, the angle
ZLOCIziOD WELLC ENT IzLOCPIZROD WELL subtended by the locations of the two
production wells through
PR
inner zone centroid CENTiz 298 is at least 90 degrees (or at least 100 degrees
or at least 110 degrees or at
least 120 degrees). When outer inner zone production wells having respective
locations
LOC PROD_WELL Z1 and LOCpRop_wELL z2 are 'are on different sides' of outer
zone 214 having outer zone
centroid CENToz 296, the angle ZLOC PRZO1 D WELLCENTozLOC E :02D WELL
subtended by the locations of the
two production wells through outer zone centroid CENTiz 298 is at least 90
degrees.
When two production wells having respective locations LOCpRop_wELL/ and
LOCpRop_wELL2 are
'are on different sides' of inner zone 210 having centroid CENTiz 298, the
angle
ZLOCP1ROD WELLCENTIzLOCP2 ROD WELL subtended by the locations of the two
production wells through
inner zone centroid CENToz 296 is at least 90 degrees.
(N) A majority or a substantial majority of heaters within inner zone 214 are
distributed on a
triangular or rectangular (e.g. square) or hexagonal pattern. In some
embodiments, this allows for more
efficient heating of inner zone 210;
For identical heaters spaced on a triangular heater well pattern, all
operating at constant power,
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the time tpyr to heat the formation to pyrolysis temperature by thermal
conduction is approximately:
tpyr c D2/D
spacing well (EQN 1)
5 where Dspacmg is the spacing between adjacent heater wells, Dwell is the
diameter of the heater wells, and c
is a proportionality constant that depends on the thermal conductivity and
thermal diffusivity of the
formation.
As noted above, heaters are deployed at a relatively high density within inner
zone 210 and at a
10 relatively low density within inner zone 214. Similarly, an 'average
spacing between neighboring
heaters' within the outer zone 214 significantly exceeds that of the inner
zone 210.
In some embodiments, the amount of time required to pyrolyze kerogen (and/or
to carry out any
other in-situ hydrocarbon production process ¨ for example, producing
hydrocarbon fluids from tar sands)
15 is substantially less in the inner zone 210 than in the outer zone due
to the relatively high heater density
and/or relatively short heater spacing in the inner zone 210.
FIGS. 4-7 present illustrative production functions describing a time
dependence of the
hydrocarbon production rate in a subsurface hydrocarbon formation according to
one illustrative
20 example. It is expected that a production function sharing one or more
feature(s) with that illustrated in
FIGS. 4-7 may be observed when producing hydrocarbons using a two-level heater
cell ¨ for example, a
two-level heater cell having feature(s) similar that of FIG. 2D.
A number of illustrative hydrocarbon production functions related to two-level
heater cells are
presented in FIGS. 4-7. In particular, the time dependence of hydrocarbon
fluid production rate in (i) the
25 inner zone 210 (see inner zone production rate curve 354); (ii) outer
zone 214 (see outer zone production
rate curve 358); (iii) the 'combined' region defined as the combination of
inner 210 and outer 214 zones
¨ this is equivalent to the area enclosed by a perimeter 208 of the outer zone
(see combined region
production rate curve 350), are all presented in accordance with this
illustrative example.
Because of the relatively 'close' heater spacing in the inner zone 210 (i.e.
in the example of FIG.
30 2D, the heater spacing in inner zone 210 is exactly one-half that of
outer zone 214), temperatures in the
inner zone 210 rise more rapidly than in the outer zone 214, so as to expedite
the production of
hydrocarbons in the inner zone 210. In contrast, in most locations in the
outer zone 214, a 'hydrocarbon
production temperature' (e.g. a pyrolysis temperature) is reached only after a
significant time delay.
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In the example of FIG. 4, an inner zone production rate peak 310 occurs before
an outer zone
production rate peak 330. During the intervening time period, a production dip
may be observed. In
other examples, it may be possible to minimize and/or eliminate the production
dip ¨ for example, by
controlling (e.g. reducing) the power level of inner zone heaters 226 relative
to those 228 in outer zone
214..
Roughly speaking, the production rate peak occurs when a particular zone or
region reaches
'hydrocarbon production temperature' ¨ e.g. a pyrolysis temperature and/or a
temperature where fluids
are mobilized in a heavy oil formation and/or bitumen-rich formation and/or
tar-sands formation.
As illustrated in FIG. 4, a production peak 330 of function 358 describing
production in outer
zone 214 occurs after a production peak 310 of function 354 describing
production in inner zone 210.
Thus, it may be said that for a two-level heater cell having zones 210, 214
(which may be written as
{ZoneliZone2] where Zonei is the innermost zone (or inner zone 210) and Zone2
is the first zone outside
of the innermost zone (or zone 214) that sequential production peaks
1Peaki,Peak2] (labeled respectively
as 310 and 330 in FIG. 4) are observed respectively at times t2/. An amount
of time required to ramp
up to the ith peak Peak, is
For the example of FIG. 4, (i) the amount of time required to ramp up to the
production peak
Peaki (labeled as 310 in FIG. 12) for the innermost zone Zonei (i.e. inner
zone 210) is (ti-to); and (ii) the
amount of time required to ramp up to the production peak Peak2 (labeled as
330 in FIG. 4) for the zone
Zone2 (i.e. outer zone 214) immediately outside of the innermost zone 210 is
(t240).
¨ )
A peak time ramp-up time ratio between these two quantities is 2
. Inspection of FIG. 4
(ti ¨ t0)
indicates that for the example FIG. 4, this ramp-up time ratio is about three.
In some embodiments, this
peak time ramp-up ratio is about equal to a zone area ratio between areas of
the more outer zone Zone2
(i.e. outer zone 214) and the more inner zone Zonei (i.e. inner zone 210). For
the example of FIG. 2D, a
'zone area ratio' between (i) an area of the more outer zone Zone2 (i.e. outer
zone 214) ; and (ii) an area
of the more inner zone Zonei (i.e. inner zone 210) is three. Thus, in some
embodiments, for a more inner
zone Zonei (e.g. inner zone 210) and a more outer zone Zone2 (i.e. outer zone
214), a 'zone area ratio'
thereof is substantially equal to a `ramp-up time' ratio for times of their
production Peaki peaks and
Peak2. In some embodiments, this is true at least in part because a reciprocal
of a 'density ratio' between
heater densities in the more outer (i.e. outer zone 214) and the more inner
zone (i.e. outer zone 214) is
also equal to the ramp-up is also equal to about three.
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Also illustrated in FIGS. 4 and 7 is the overall or total rate of hydrocarbon
fluid in the 'combined
region' (i.e. the area enclosed within outer zone perimeter 208 ¨ this is the
combination of inner 210 and
outer 214 zones), described by curve 350 having a production rate peak 320
which occurs immediately
before that 330 of outer zone 2140.
Inspection of combined region hydrocarbon fluid production rate curve 350
indicates that: (i)
similar to inner zone production curve 354, combined region production curve
350 ramps up relatively
quickly indicating a fast rise time; (ii) a 'significant' hydrocarbon
production rate (e.g. at least one-half
of the maximum production rate) is sustained for a relatively long period of
time. In the example of FIGS.
4 and 7, a ratio SPT/RT between a (i) a sustained production time SPT (i.e.
the amount of time that the
production rate is contiuously sustained above one-half of a maximum
production rate level for the
combined region) and (ii) a rise time RT for the combined region is relatively
'large' ¨ e.g. at least
four-thirds or at least three-halves or at least two.
For the present disclosure, a 'half-maximum hydrocarbon fluid production rate
rise time' or
'half-maximum rise time' is the amount of time required for hydrocarbon fluid
production to reach
one-half of its maximum, while the 'half-maximum hydrocarbon fluid production
rate sustained
production time' or the 'half-maximum sustained production time' is the amount
of time where the
hydrocarbon fluid production rate is sustained at least one-half of its
maximum. FIGS. 5, 6 and 7
respectively show production rate curves 354, 358 and 350 for the inner 210,
outer 214 and 'total' zones
(i.e. the combination of inner and outer zones).
In FIGS. 4-7, a production dip (e.g. occurring after peak 310 and before peak
330) is illustrated.
¨In some embodiments, such a production dip (or any other production dip) may
be observed even within
a time period of a 'half-maximum hydrocarbon fluid production rate sustained
production time' as long
as the production rate remains above one-half of a maximum rate throughout the
time period of the
'half-maximum hydrocarbon fluid production rate sustained production time'.
A relatively large SPT/RT ratio may describe situations where, (i) hydrocarbon
fluids are
produced (e.g. from kerogen or from bitumen) and removed from the subsurface
after only a minimal
delay, allowing a relatively rapid 'return' on investment in the projection
while using substantially only a
minimal number of heaters; and (ii) hydrocarbon fluids are produced for a
relatively extended period of
time at a relatively constant rate. Because hydrocarbon fluids are produced at
a relatively constant rate, a
ratio between a peak hydrocarbon production rate and an average hydrocarbon
production rate for the
combined region, is relatively small. In some embodiments, the amount of
infrastructure required for
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hydrocarbon fluid production and/or processing is determined at least in part
by the maximum
production rate. In some embodiments, a relatively low ratio between a peak
hydrocarbon production
rate and an average hydrocarbon production rate for the combined region may
reduce the amount of
infrastructure required for fluid production and/or processing with a minimal
number, or near minimal
number, of pre-drilled heater wells.
It is is appreciated that none of the examples relating to illustrative
production functions are
limiting. It may be possible to change the shape of this function, for
example, by operating heaters at
different power levels.
Also illustrated in FIG. 14A are the earlier 980 and later 984 stages of
production. During the
earlier 980 stage of production, hydrocarbon fluids are produced primarily in
inner 210 zone; during the
later 984 stage of production, hydrocarbon fluids are produced primarily in
outer 214 zone.
FIG. 12E is a flowchart of a method for producing hydrocarbon fluids. In step
S1551, wells are
drilled into the subsurface formation. In step S1555, heaters are installed in
the heater wells ¨ it is
appreciated that some heaters may be installed before all heater wells or
production wells are drilled.
In step S1559, the pre-drilled heaters are operated to produce hydrocarbon
fluids such that a ratio
between a half-maximum sustained production time and a rise time is at least
four-thirds, or at least
three-halves, or at least seven quarters or at least two. In some embodiments,
this is accomplished using
any inner zone and outer zone heater pattern disclosed herein. In some
embodiments, at least a majority
of the outer zone heaters commence operation when at most a minority of inner
zone hydrocarbon fluids
have been produced.
In some embodiments, any heater pattern disclosed herein (e.g. relating to two-
level heater cells)
may be thermally efficient. In particular, in some embodiments, at least 5% or
at least 10% or at least
20% of the thermal energy used for outer zone hydrocarbon fluid production is
supplied by outward
migration (e.g. by heat conduction and/or convection) of thermal energy from
the inner zone 210 to the
outer zone 214.
Once the production rate in the inner zone has dropped by a certain threshold
(for example, by at
least 30% or at least 50% and/or at most 90% or at most 70% of a maximum
production rate), this may
indicate that a hydrocarbon fluid production temperature (e.g. a temperature
which results in mobilized
fluids, visbreaking, and/or pyrolysis of hydrocarbon-containing material so
that mobilized fluids,
visbroken fluids, and/or pyrolyzation fluids are produced in the formation)
has been reached throughout
most of the inner 210 zone ¨ e.g. a pyrolysis temperature or a temperature for
mobilizing hydrocarbon
fluids), even when significant portions of the outer 214 zone (e.g. at least
30% of or a majority of) are at
a significantly cooler temperature. Studies conducted by the present inventors
indicated that once this
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inner-zone production drop has occurred, the ability of the inner-zone heaters
to expedite fluid
production is significantly reduced, and thus further full-power operation of
the inner-zone heaters may
be of only marginal utility, and may not justify the energy 'cost.'
In some embodiments, it is useful to shut off and/or reduce power to the inner
zone heaters even
while the outer zone heaters continue to operate at about the same power
level.
As illustrated in FIG. 8, in some embodiments, the heater pattern of FIG. 2A,
or of any other
embodiment disclosed herein (for example, see any of FIGS. 2-3) may repeat
itself. Thus, in some
embodiments, any inner zone-outer zone heater pattern disclosed herein may be
a 'unit cell' heater
pattern which repeats itself. Since any heater pattern disclosed herein (and
any feature(s) thereof or
combination thereof) may also be a 'heater well pattern,' the heater well
pattern of FIG. 2A, or of any
other embodiment disclosed herein, may repeat itself.
In the example of FIGS. 8, the heater pattern of FIG. 2A exactly repeats
itself in each cell so as to
fill space of a subsurface formation ¨ i.e. the unit heater cells are
identical. As illustrated in the example
of FIGS. 11-12, the 'identical cell' feature is not a limitation and heater
cells are not required to be
exactly repeating unit cells. In some embodiments, each heater cell may
individually provide common
features (i.e. any combination of features disclosed herein including but not
limited to features related to
heater spacing features, heater spatial density feature(s), features related
to size(s) and/or shape of inner
and/or outer zones (or relationships between them), production well features,
features relating to
operation of heaters or any other feature).
In the example of FIGS. 11-12, for each heater cell, an area enclosed by outer
zone perimeter 208 is
about four times that of inner zone perimeter 204, a heater density within
inner zone 210 significantly
exceeds that of outer zone 214, at least a substantial majority of the inner
zone heaters 226 are located
away from outer zone perimeter 208, production well(s) are located in each of
inner 210 and outer 214
zones.
In the example of FIGS. 8-12, for a plurality of the heater cells, (i) the
area of all cells are
substantially equal to a single common value; (ii) for each heater cell of the
plurality of cells, a
significant portion (i.e. at least one third or at least one half or at least
two-thirds or at least three-quarters)
of each cell perimeter (e.g. outer zone perimeter 208) is located 'close' to a
neighboring cell perimeter.
A 'candidate location' of a first heater cell (i.e. within the cell or on a
perimeter thereof - e.g. cell A
610) is located 'close to' a second heater cell (e.g. cell B 614 or C 618) if
a distance between (i) the
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'candidate location' of the first heater cell and (ii) a location of the
second heater cell that is closest to the
'candidate location' of the first heater cell is less than a 'threshold
distance.' Unless otherwise specified,
this 'threshold distance' is at most two-fifths of a square root of an area of
the first heater cell. In some
embodiments, this 'threshold distance' is at most one third or at most one
quarter or at most one sixth or
5 at most one tenth of a square root of an area of the first heater cell.
In some embodiments, for each of first and second neighboring heater cells
(e.g. having
substantially equal areas), at least a portion (e.g. at least 5% or at least
10% or at least 20% or at least 30%
or at least 40% or at least a majority of) of each cell perimeter selected
from one of the first and second
10 heater cells) is 'close' to the other heater cell.
In the example of FIG. 8, one of the cells is a 'surrounded cell' whereby an
entirety of its perimeter
is 'close to' neighboring heater cells. For the present disclosure, a heater
cell is 'substantially
surrounded' when a substantial majority (i.e. at least 75%) of its perimeter
is 'close to' a neighboring
15 heater cell. In the example of FIG. 8, different portions of a perimeter
of surrounded cell 608 are 'close
to' six different neighboring heater cells. In some embodiments, different
portions of a perimeter of
surrounded cell 608 are 'close to' at least 3 or at least 4 or at least 5
different neighboring cells ¨ e.g. a
majority of which or at least 3 or at least 4 or at least 5 of which have an
area that is 'substantially equal'
to that of surrounded cell 608.
Also labeled in FIG. 8 are first 602 and second 604 neighboring cells, which
are located on
opposite sides of surrounded cell 608. In the present disclosure, two
neighboring cells CELLINE/GHBoR
2 NEIGHBOR)
and CELL2 NEIGHBOR having respective centroids CENT(CELLINEIGHBoR) and
CENT(CELL are said to
be 'substantially on opposite sites' of a candidate heater cell CELLcANDIDATE
having a centroid
CENT(CELLcAND/DATE) if an angle ZCENT (CELL
1NEIGHBOR)CENT (CELL CANDIDATE)CENT (CELL
2NEIGHBOR) is
at least 120 degrees. In some embodiments, this angle is at least 130 degrees
or at least 140 degrees or at
least 150 degrees.
One salient feature of the multi-cell embodiment of FIG. 8-12 is that
neighboring cells may 'share'
one or more (e.g. at least two) common outer perimeter heaters 236. In this
situation, each of the shared
heater serves as an outer perimeter heater for two or more neighboring cells.
In the example of FIG. 8,
neighboring heater cells may share up to three common outer perimeter heaters.
Without limitation, in some embodiments, the multi-cell pattern based upon
nested hexagons (e.g.
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having two levels as illustrated in FIG. 8 or having three or levels as
discussed below) may provide one
or more of the following benefits: (i) a significantly lower heater well
density (e.g. at most three-thirds or
at most three-fifths or at most one-half) compared to what would be observed
for the hypothetical case
where all heaters were arranged at a uniform density equal to that of the
inner zones 210; (ii) a relatively
short time to first production (e.g. see FIG. 4-7); (iii) a lower energy use
due to heat exchange between
zones and/or between neighboring cells; and/or (iv) due to the presence of
production wells in inner
zones as well as outer zones, more oil and less gas is produced because fluids
pas near fewer heater wells
en route to a production well ¨ hence, less cracking.
It appreciated that other embodiments other than that of FIG. 8 may provide
some or all of the
aforementioned benefits.
The pattern of FIG. 9 is similar to that of FIG. 8 ¨ however, in the example
of FIG. 9 production
wells are arranged at the centroid 296, 298 of each heater cell, while in the
example of FIG. 8 heaters are
arranged at the centroid 296, 298 of each heater cell.
In FIG. 10, a region of subsurface formation is filled with multiple heater
cells including cell "A"
610, cell "B" 614 and cell "C" 618. As illustrated in FIG. 10, cells "A" 610
and "C" 618 share common
outer zone perimeter heater "W" 626; cells "A" 610 and "B" 614 share common
outer zone perimeter
heater "X" 639; cells "B" 614 and "C" 618 share common outer perimeter heater
"Y" 638.
As illustrated in FIGS. 12-13, in some embodiments, the heater cells do not
have identical patterns,
and the heater cells may be thought of as 'quasi-unit cells' rather than 'unit
cells.' In the example of FIGS.
12-13, even though heater cells are not identical, each heater cell
individually may contain any
combination of feature(s) relating to inner 210 and outer 214 zones described
in any embodiment herein.
The features include but are not limited to features related to heater spacing
(e.g. shorter average spacing
between neighboring heaters in inner zone 214 than in outer zone 210), heater
density (e.g. higher
density in inner zone 214 than in outer zone 210), dimensions of inner and/or
outer zone perimeters 204,
208 (e.g. related to aspect ratio, or related to a ratio between respective
areas of outer and inner zones or
of areas enclosed by perimeters 204, 208 thereof), average distance to a
nearest heater, dispersion and/or
distribution of heaters within inner and/or outer zone, heater distribution
along inner and/or outer zone
perimeter(s) 204, 208, or any other feature (e.g. including but not limited to
feature(s) related to heater
location).
In the example of FIGS. 12-13, neighboring cells all have like-shaped and like-
sized inner zone
and outer zone perimeters 204, 208. This is not a limitation. In some
embodiments, areas or aspect ratios
of inner zone and/or outer zone perimeters 204, 208 of neighboring cells (i.e.
which optionally share at
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least one common outer zone heater) may be similar but not identical. In some
embodiments, for any
'cell' pair CELLi, CELL2 of neighboring heater cells CELLi, CELL2 an area
enclosed by inner zone
and/or outer zone perimeters 204, 208 of CELLi is (i) equal to at least 0.5
times and at most 2.0 times
that of CELL2 or (ii) equal to at least 0.666 times and at most 1.5 times that
of CELL2; or (iii) equal to at
least 0.8 and at most 1.2 times that of CELL2 In some embodiments, for any
pair of neighboring heater
cells CELLi, CELL2 an aspect ratio of inner zone and/or outer zone perimeters
204, 208 of CELLi is (i)
equal to at least 0.5 times and at most 2.0 times that of CELL2 or (ii) equal
to at least 0.666 times and at
most 1.5 times that of CELL2; or (iii) equal to at least 0.8 and at most 1.2
times that of CELL2
In some embodiments, any feature(s) in the previous paragraph relating any
pair of neighboring
heater cells CELLi, CELL2 may be true for at least one pair of neighboring
heater cells CELLi, CELL2. In
some embodiments, any feature(s) may be true for various pair sets of cells.
For example, if a cell
CELLGNEN surrounded by a plurality of neighbors CELLNE/GHBoRJ, CELLNE/GHBoR_2,
= = = CELLNEIGHBOR_N,
any feature(s) of the previous paragraph previous paragraph may be true for at
least a majority, or for all
of the following cell pairs: { CELLG/vEN, CELLNE/GHBoR_/}, ICELLGIVEN,
CELLNEIGHBOR_2 I = = =
CELLGIVEN, CELLNEIGHBOR_N} =
In some embodiments, a region of the subsurface formation (i.e. a two-
dimensional portion of a
cross-section of the subsurface formation) may be 'substantially filled' by a
plurality of heater cells if at
least 75% or at least 80% or at least 90% of the area of the region is
occupied by one of the heater cells.
In some embodiments, the 'cell-filled-region' includes at least 3 or at least
5 or at least 10 or at least 15 or
at least 20 or at least 50 or at least 100 heater cells and/or is rectangular
in shape and/or circular in shape
or having any other shape and/or has an aspect ratio of at most 3 or at most
2.5 or at most 2 or at most 1.5.
In some embodiments, any feature(s) relating pairs of neighboring cells (i.e.
relating to the sharing of
outer perimeter heaters 236 or related to neighboring pairs of heaters CELLi,
CELL2 }) may be true for
a majority of heater cells (or at least 75% of the heater cells or at least
90% of the heater cells) within the
cell-filled region. In some embodiments, both a 'length' and a 'width' of the
cell-filled region (i.e.
measured in heater cells) may be at least 3 or at least 5 or at least 10 or at
least 20 heater cells.
FIGS. 2-12 relate to heater patterns having at least two 'levels' ¨ i.e. an
inner zone 210 having
relatively high heater density and an outer zone 214 having relatively low
heater density. In the
examples of FIGS. 13-14, one or more heater cells have at least 'three'
levels.
OZS additional zone heaters (i.e. heaters located OZS additional zone
perimeter 202 or in an
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interior of OZS additional zone 218) include OZS additional zone perimeter
heaters each located on or
near OZS additional zone perimeter 202 and distributed around OZS additional
zone perimeter 202. In
some embodiments, OZS additional zone heaters are predominantly OZS additional
zone perimeter
heaters ¨ this is analogous to the feature provided by some embodiments and
described above whereby
outer zone heaters 228 are predominantly outer zone perimeter heaters 236.
For the present disclosure, the OZS 210 refers to the entire area enclosed by
a perimeter 202
thereof. that is also outside of outer zone 214.
In the example of FIG. 13, an area enclosed by a perimeter 202 of OZS
additional zone 218 and
four times that of outer zone perimeter 202, and an average heater spacing
within OZS additional zone
218 is about twice that of outer zone 214. In the example of FIG. 13,
perimeters 204, 208, 202 of inner,
outer and OZS-additional zones 210, 214, 218, are regular-hexagonal in shape
and have respective side
lengths equal to 2s, 4s, and 8s. In the example of FIG. 13, respective average
heater spacings of inner 210,
outer 214, and OZS additional 218 zones are equal to s, approximately equal to
2s, and approximately
equal to 4s. In different embodiments, a perimeter 202 of OZS additional zone
218 is convex or
substantially convex.
In different embodiments, a relation between OCS additional zone 218 and outer
zone 214 is
analogous to that between outer zone 214 and inner zone 210. Thus, in some
embodiments, by analogy,
any feature described herein a relationship between inner 210 and outer 214
zones may also be provided
for outer 214 and OZS additional 218 zones. Such features include but are not
limited to features related
to heater spacing (e.g. shorter average spacing between neighboring heaters in
inner zone 214 than in
outer zone 210), heater density (e.g. higher density in inner zone 214 than in
outer zone 210), dimensions
of inner and/or outer zone perimeters 204, 208 (e.g. related to aspect ratio,
or related to a ratio between
respective areas of outer and inner zones or of areas enclosed by perimeters
204, 208 thereof), average
distance to a nearest heater, dispersion and/or distribution of heaters within
inner and/or outer zone,
heater distribution along inner and/or outer zone perimeter(s) 204, 208, or
any other feature (e.g.
including but not limited to feature(s) related to heater location).
As was noted above for the case of a perimeter 208 of outer zone 214, in
different embodiments the
perimeter 202 of OZS additional zone 218 may be defined by locations of the
heater (i.e. to form some a
ring-shaped cluster where adjacent locations have a significantly lower heater
density).
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In the example of FIG. 13, production wells 224 are arranged through each of
inner 210, outer
214, and OZS additional zone 218, and are respectively labeled in FIG. 13 as
inner zone 2241, outer zone
2240 and additional zone 224A production wells. In the example of FIG. 13, the
density of production
wells is greatest in the most inner zone (i.e. inner zone 210), is the least
in the most outer zone (i.e.
additional zone 218) and has an intermediate value in the 'mediating' zone
(i.e. outer zone 214). In
particular, a ratio between an inner zone production well density and that of
outer zone 210 is three; a
ratio between an outer zone production well density and that of additional
zone 214 is also three.
In the particular example of FIG. 13, perimeters 208, 202 of outer 214 and OZS-
additional 218
zones are like shaped. As illustrated in FIGS. 13-14, this is not a
limitation.
Even though perimeters 208, 204 of outer 214 and inner 210 zones are not
required to be
like-shaped but they may share certain shape-properties ¨ for example, an
aspect ratio (see, for example
FIGS. 10A-10B) or any other shape-related parameter discussed herein.
Embodiments of the present invention relate to patterns of 'heaters.' The
heaters used may be
electrical heaters, such as conductor-in-conduit or mineral-insulated heaters;
downhole gas combustors;
or heaters heated by high temperature heat transfer fluids such as superheated
steam, oils, CO2, or molten
salts or others. Because the outer zones 214 of heaters may be energized for a
substantially longer time
than the inner zone of heaters, for example, four times or eight times longer
(see FIG. 13A), a heater with
high reliability and long life is preferred for the outer 214 or OZS
additional 218 zones. Molten salt
heaters have very long lifetimes because they operate at nearly constant
temperature without hot spots,
and in many chemical plant and refinery applications, molten salt heaters have
been operated for decades
without shutdown. In addition, molten salt heaters may have very high energy
efficiency, approaching
80%, and over the lifetime of the reservoir most of the thermal energy will be
supplied to the oil shale
from the heaters in the zones with the longest spacing.
FIG. 15A is an image of an exemplary electrical heater. FIG. 15B is an image
of an exemplary
molten salt heater. FIG. 15C is an image of an exemplary downhole combustion
heater; FIG. 15D is a
cross section of the downhole portion of the the heater of FIG. 15C. For an
additional discussion of types
of heaters and various features thereof, the skilled artisan is referred to US
patent 7,165,615, US patent
6,079,499, US patent 6,056,057 and US patent publication 2009/0200031, which
are all incorporated
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herein by reference in their entireties. In some embodiments, molten salt is
continuously flowed through
the heater. For example, hot molten salt (e.g. heated by a gas furnace) may be
continuously forced
through the molten salt heater to replace the thermal energy lost by the
molten salt within the heater to the
formation.
5
A schematic of an advection-based heater is illustrated in FIG. 15E.
Although the source of hot
heat transfer fluid is illustrated in the figures as above the surface, this
is not a requirement - alternatively
or additionally, it is possible to heat the heat transfer fluid at one or more
subsurface location(s).
FIGS. 16A-16D relate to 'heaters powered primarily by fuel combustion'. In the
example of FIG.
16A, a fuel (e.g. a fossil fuel) is combusted, thermal energy of the fuel
combustion generates steam which
10
drives a steam turbine to produce electricity. The electrical heater (for
example, similar to FIG. 15A) is
powered by the fuel-combustion-derived electricity. Examples of fuels which
may be combusted include
but are not limited to methane, natural gas, propane, flue gas, coal and
hydrogen gas. In the example of
FIG. 16B, a gas turbine powered by gas combustion generates electricity
supplied to the electrical heater.
Other examples of "heaters powered primarily by fuel combustion" are
illustrated in FIGS. 16C-16D (i.e.
15
a particular case of the heater of FIG. 15E) where the generated
electricity (i.e. from the steam turbine or
the gas turbine) is used to resistively heat a material (e.g. a ferromagnetic
material) in thermal contact
with a heat transfer fluid (one example of a heat transfer fluid is a molten
salt; another example is a
synthetic oil; another example is molten metal). In the example of FIGS. 16C-
16D, the heat transfer fluid
is heated above the surface where the resistively-heated material (i.e. which
receives electrical current
20
derived from combustion of fossil fuel) is located within an above-
surface storage tank. This is not a
limitation. Alternatively or additionally, the heat transfer fluid may be
heated in the subsurface - e.g. the
resistively-heated material through which electrical current flow (i.e.
electrical current derived from fuel
combustion) may be located in the subsurface. The examples of FIGS. 16A-216D
relate to the situation
wherein thermal energy of combustion is used to generate electricity. This is
not a limitation. Other
25
examples of 'heaters powered primarily by combustion' are illustrated in
FIGS. 15C-15D discussed
above.
In contrast to the heaters of FIGS. 15C-15D and 16A-16D which are 'heaters
powered primarily
by combustion,' the heaters of FIGS. 17A-17B are powered 'primarily by
electricity generated from
wind.' In the example of FIG. 17A, electricity generated from wind is used to
resistively heat a material
30
(e.g. a ferromagnetic material) in thermal communication with a heat
transfer fluid. In the example of
FIG. 17A, the heat transfer fluid is heated above the surface where the
resistively-heated material (i.e.
which received electricity derived from wind) is located in an above-surface
fluid storage tank. This is
not a limitation. Alternatively or additionally, the heat transfer fluid may
be heated in the subsurface - e.g.
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the resistively-heated material (i.e. through which electrical current
generated from wind) may be located
in the subsurface. In the example of FIG.17B, an electrical heater is powered
by electricity generated
from wind.
Any electrical heater may include a voltage control system (NOT SHOWN).
In some embodiments, the turbine may be a microturbine - for example,
available from the
Capstone Turbine Corporation (United States).
Reference is now made to FIG. 18-19. In the inner zone, at least a majority or
at least 2/3 of the
heaters are powered primarily by electricity from wind.
In contrast, in the outer zone a majority of at least 2/3 of the heaters are
powered primarily by fuel
combustion - hot fluids from the combusted fuel may be directly circulated
within the subsurface (see
FIGS. 15C-15D) or thermal energy from the fuel combustion may be used to
generate electricity (see
FIGS. 16A-16C).
Reference is now made to FIG. 20-21. In the inner zone, at least a majority or
at least 2/3 of the
heaters are powered primarily by fuel combustion - hot fluids from the
combusted fuel may be directly
circulated within the subsurface (see FIGS. 15C-15D) or thermal energy from
the fuel combustion may
be used to generate electricity (see FIGS. 16A-16C).
In contrast, in the outer zone at a majority or at least 2/3 of at least a
substantial majority of the
heaters are powered primarily by electricity generated from wind.
Some embodiments relate to 'neighboring heaters' or 'average spacing between
neighboring
heaters.' Reference is made to FIGS. 22A-B. In FIG. 22A, heaters are arranged
according to the same
heater pattern as in FIGS. 2A-2D, and heaters are labeled as follows: seven of
the outer perimeters
heaters are labeled 220A-220G, and nine of the inner zone heaters are labeled
as 22011-220P. FIG. 22B
illustrates a portion of the heater pattern of FIG. 22A.
It is clear from FIG.22A that some heaters may be said to 'neighbor each
other' (for example,
heaters 220C and 220D are 'neighbors,' heaters 220C and 220J are 'neighbors,'
heaters 220J and 220K
are 'neighbors') while for other heaters, this is not true. Heaters 220C and
220L of the 'heater pair'
(220C,220L) are clearly not 'neighbors.' This is because 'heater-connecting-
line segment'
Seg_Connect(220C,220L) connecting heaters (i.e. connecting the centroids of
their respective cross
sections) of the pair (220C,220L), having a length 2Nis , crosses at least one
shorter
'heater-connecting-line segment,' as illustrated in FIG. 22B. In particular,
'heater-connecting-line
segment' Seg_Connect(220C,220L) crosses (i) Seg_Connect(220D,220K) having a
length of 1/,s' and
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(ii) Seg_Connect(220D,220J) having a length of 2s.
FIG. 22C illustrate the same heaters as in FIG. 22B ¨ line segments of
'neighboring heater pairs'
are illustrated. In the example of FIG. 22C, the neighboring heater pairs are
as follows: {Heater 220C,
Heater 220D}; { Heater 220D, Heater 220E}; { Heater 220E, Heater 220L}; {
Heater 220K, Heater 220L};
{ Heater 220J, Heater 220K}; { Heater 220C, Heater 220J}; { Heater 220D,
Heater 220J}; { Heater 220D,
Heater 220K}; { Heater 220D, Heater 220L},
FIG. 23A illustrates the same heater pattern as that of FIGS. 2A-2D and FIG.
22A. In FIG. 22C,
lines between neighboring heaters are illustrated. Within the outer zone 214,
the average line length, or
the average 'heater spacing' is around 1.95s, or slightly less than 2s. Within
the inner zone 210, the
average line length, or the average 'heater spacing' is exactly s.
FIG. 23B illustrates 'connecting line segments' between neighboring heaters
.Within the inner
zone 210 of the example of FIG. 23B, the average line length, corresponding to
the average heater
spacing, is exactly s.
Two heaters HeaterA, HeaterB are 'neighboring heaters' if the connecting line
segment between
them (i.e. between their respective centroids) does not intersect a connecting
line segment between two
other heaters Heaterc, HeaterD in the subsurface formation. A 'heater-
connecting-line-segment between
neighboring heaters' is 'resident within' a region of the subsurface formation
(i.e. a two-dimensional
cross-section thereof) if a majority of the length of the 'heater-connecting-
line-segment' is located within
the region of the subsurface formation.
FIGS. 23C-24 respectively illustrate 'connecting lines' between neighboring
heaters.
For the present disclosure, an 'average spacing between neighboring heaters'
and an 'average
heater spacing' are used synonymously.
Embodiments of the present invention relate to inner perimeter heaters 232,
outer perimeter heaters
236 and `OZS additional zone perimeter heaters.' As discussed earlier, in some
embodiments, the
locations of the heaters determine the locations of the perimeters 204, 208
(and by analogy 202) of inner
210, outer 214 or OZS additional 218 zones. In this case, inner perimeter
heaters 232, outer perimeter
heaters 236, and OSC-additional-zone perimeter heaters respectively are
located on perimeters 204, 208,
202.
Alternatively, these perimeters 204, 208, 202 may be determined by a
predetermined shape ¨ e.g. a
rectangle or regular hexagon or any other shape. For the latter case, there is
no requirement for the inner
perimeter heaters 232 to be located exactly on inner zone perimeter 204 ¨ it
is sufficient for the heater to
be located near inner perimeter - e.g. in a 'near-inner-perimeter' location
within inner zone 210 or within
outer zone 214. By analogy, the same feature is true for outer zone perimeter
208 or OZS-additional zone
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perimeter 202.
This is illustrated in FIGS. 25A-25B which illustrate: (i) locations in the
interior 610 of the inner
zone 210; (ii) locations 614 in inner zone 210 that are 'substantially on'
inner zone perimeter 204; (iii)
locations 618 in outer zone 214 that are 'substantially on' inner zone
perimeter 204; (iv) locations 622 in
the interior of the 'interior' of outer zone 214 (i.e. away from both inner
zone and outer zone perimeters
204, 208); (iv) locations 626 in outer zone 214 that are 'substantially on'
outer zone perimeter 208; (v)
locations 626 outside of outer zone 214 that are 'substantially on' outer zone
perimeter 208.
For each candidate location 614 in inner zone 210 that is 'substantially on'
inner zone perimeter
204, a ratio between (i) a distance from the candidate location 614 to a
nearest location on inner zone
perimeter 204 and (ii) a distance from the candidate location 614 to a
centroid of inner zone 210 (i.e. the
area enclosed by inner zone perimeter 204) is at most 0.25 or at most 0.2 or
at most 0.15 or at most 0.05.
For each candidate location 618 in outer zone 214 that is 'substantially on'
inner zone perimeter
204, a ratio between a (i) distance from the candidate location 618 to a
nearest location on inner zone
perimeter 204 and (ii) a distance from the candidate location 618 to a nearest
location on outer zone
perimeter 208 is at most 0.25 or at most 0.2 or at most 0.15 or at most 0.05.
For each candidate location 626 in outer zone 214 that is substantially on
outer zone perimeter 208,
a ratio between (i) a distance from the candidate location 626 a nearest
location on outer zone perimeter
208 and (ii) a distance from the candidate location 626 to a nearest location
on inner zone perimeter 204
is at most 0.25 or at most 0.2 or at most 0.15 or at most 0.05.
For each candidate location 630 outside of outer zone perimeter 208 that is
substantially on outer
zone perimeter 208, a ratio between (i) a distance from the candidate location
630 a nearest location on
outer zone perimeter 208 and (ii) a distance from the candidate location 630
to a centroid 298 of the area
enclosed by outer zone perimeter 208 is at most 1.25 or at most 1.15 or at
most 1.05.
Reference is now made to FIG. 26A-26B. As noted above, when heaters 'are
distributed' around
perimeter 208 of outer zone 214, this means that heaters (i.e. which are
located on or near outer zone
perimeter 208) are present on every 90 degree sector of outer zone perimeter
208.
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This is illustrated in FIGS. 26A-26B. In FIG. 26A, it is possible to divide
the cross-area of the
subsurface formation into four 'quadrants' corresponding to four 90 degree
sectors (i.e. since the
quotient of 360 degrees and four is 90 degrees) relative to any arbitrary
'reference ray 316' starting at
centroid of outer zone 214. FIGS. 26A-26B illustrate respective orientations
of reference ray 316.
After the orientation of reference ray 316 relative to the heater pattern is
fixed, it is possible to
define the cross section of the subsurface formation, relative to ray 316,
into four quadrants Q1 160, Q2
162, Q3 164, and Q4 166. Dividing the subsurface formation into four quadrants
also divides outer
perimeter 208 into four portions ¨ in FIG. 26A, these four portions are
defined as (i) the portion of outer
zone perimeter 208 located in Q1 160 between points 402 and 404; (ii) the
portion of outer zone
perimeter 208 located in Q2 162 between points 402 and 408; (iii) the portion
of outer zone perimeter
208 located in Q3 164 between points 406 and 408; (iv) the portion of outer
zone perimeter 208 located
in Q4 166 between points 406 and 404. Thus, in FIG. 26A, these four portions
are determined by four
points on outer zone perimeter 208, namely points 402, 404, 406 and 408. In
FIG. 26B associated with a
different orientation of reference ray 316, these four portions are determined
by points 422, 424, 426 and
428, all lying on outer zone perimeter 208.
For the present disclosure, when heaters are 'present' on every 90 degree
sector of outer zone
perimeter 208, then irrespective of an orientation of a reference line 316
relative to which four quadrants
are defined (i.e. for any arbitrary reference line orientation), there is at
least one outer perimeter heater
236 within each of the four quadrants. This concept can be generalized to 72
degree sectors (i.e. to divide
the subsurface cross section into five equal portions rather than four
quadrants), 60 degrees sectors (i.e.
six equal portions or 'sextants') and 45 degree sectors (i.e. eight equal
portions or 'octants').
Reference is now made to FIGS. 27-28.
Embodiments of the present invention relate to features of 'distances between
heaters' or
'distances between a heater and a location,' where 'distance' and
'displacement' may be used
interchangeably. As noted above, unless indicated otherwise, any 'distance' or
'displacement' refers to a
distance or displacement constrained within a two-dimensional cross section
for which a heater pattern is
defined ¨ for example, including but not limited to any heater pattern
illustrated in FIGS. 2-11 and 15-16.
In particular, embodiments of the present invention relate to apparatus and
methods whereby (i)
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due to the relatively 'high' heater density and to the distribution of inner
zone heaters 226 throughout
inner zone 210, a significant fraction of inner zone 210 is 'very close' to a
nearest heater; (ii) due to the
relatively 'low' heater density and to feature whereby most outer zone heaters
228 are arranged at or near
outer perimeter 208, a significantly smaller fraction of outer zone 214 is
'very close' to a nearest heater.
5
As such, the rate of production increases in the inner zone 210
significantly faster than in the outer zone
214.
Referring to FIGS. 27-28, it is noted that a 'distance between heaters' refers
to the distance
between respective heater centroids. Unless indicated otherwise, a 'heater
centroid' 310 is a centroid of
10
the heater cross-section co-planar the two-dimensional cross-section of
the subsurface where any heater
pattern feature is defined. As evidenced by FIGS. 27A-27B, heater cross-
section is not required to be
circular. As evidenced by FIGS. 27A-27B, the 'distance between heaters 220,'
which is the distance
between their respective centroids 310, is not necessarily between the
locations on the heater surface.
15
Some embodiments refer to a 'distance' or 'displacement' between a
location (indicated in FIGS.
28A-28D by an 'X') within the subsurface formation and one of the heaters.
Unless indicated otherwise,
this 'distance' or 'displacement' is: (i) the distance D within the plane
defined by the two-dimensional
cross-section of the subsurface where any heater pattern feature is defined;
(ii) the distance D between
the location 'X' and the heater centroid 310. In the examples of FIGS. 28A and
28B, the distance
20
between a location 'X' and heater 220, is defined by the distance between
heater centroid 310 and
location 'X,' even for situations where the location 'X' is within heater 220
but displaced from heater
centroid 310.
FIGS. 29A-29C illustrate the concept of a substantially convex shape. If a
candidate shape 720 is
25
convex it is, by definition, also substantially convex. If candidate shape
720 is not convex, it is possible
to determine if candidate shape 720 is substantially convex according to one
of two theoretical convex
shapes: (i) a minimum-area enclosing convex shape 722- i.e. the smallest (i.e.
of minimum area) convex
shape which completely encloses the candidate shape 720; (ii) a maximum-area
enclosed convex shape
724 - i.e. the 'largest' (i.e. of maximum area) convex shape which is
completely within candidate shape
30 720
It is possible to define a first area ratio as a ratio between (i) an area
enclosed by minimal-area
enclosing convex shape 722 and (ii) an area enclosed by candidate shape 720.
It is possible to define a
second area ratio as a ratio between (i) an area enclosed by candidate shape
720 and (ii) an area enclosed
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by maximum-area enclosed convex shape 724.
For the present disclosure, a candidate shape 720 is 'substantially convex' if
one or both of these
area ratios is at most a 'threshold value.' Unless specified otherwise, this
threshold value is at most 1.3.
In some embodiments, this threshold value may be at most 1.2 or at most 1.15
or at most 1.1 or at most
1.05.
If one or both of these area ratios is at most a value X, 'convex shape
tolerance value' of the
candidate shape 720 is said to be X. Thus, as noted in the previous
paragraphs, in different embodiments,
the 'convex shape tolerance value' is at most 1.2 or at most 1.15 or at most
1.1 or at most 1.05.
As noted above, for the present disclosure, 'spatial heater density' is
defined according to the
principles of reservoir engineering. For example, the heater FIG. 2A, nineteen
heaters are inner zone
heaters 226 located on the inner zone perimeter 204 or within inner zone 210,
while twelve heaters are
outer zone heaters 228 located on outer zone perimeter 208 or within outer
zone 214.
FIG. 30 illustrates a portion of the heater scheme of FIG. 2A, where heaters
are labeled as in FIG.
22C. For density purposes, it is possible to draw an 'immediate-neighboring-
region circle' around each
heater centroid (i.e. serving as a heater 'locator point' within a cross-
section of the subsurface formation
in which the heater (well) pattern is defined) having a circle radius equal to
one-half of a distance to a
nearest neighboring heater.
In the example of FIG. 30, the radius of immediate-neighboring-region circles
around heaters
220A, 220C and 220G, 220E and 220G (i.e. all located on vertices of outer
hexagon 208) equals a, the
radius of immediate-neighboring-region circles around heaters 220B, 220D and
220F (i.e. all located
.J
halfway between adjacent vertices of outer hexagon 208) is ¨2a , and the
radius of
immediate-neighboring-region circles around inner zone heaters 22011-220P is
¨a .
2
For the heater pattern scheme of FIG. 2A, 'outer-hexagon-vertex' heaters (see,
for example, the
outer zone heaters labeled as 220A, 220C, 220E and 220G in FIG. 30) are outer
zone heaters are located
on vertices of outer hexagon 208, 'outer-hexagon-mid-side' heaters (see, for
example, the outer zone
heaters labeled as 220B, 220D and 220F in FIG. 30) are outer zone heaters
located midway between
adjacent vertices of outer hexagon 208, 'inner-hexagon-vertex' heaters (see,
for example, the inner zone
heaters labeled as 22011, 220J, 220L and 220N in FIG. 30) are inner zone
heaters are located on vertices
of inner hexagon 204, and 'inner-hexagon-mid-side' heaters (see, for example,
the outer zone heaters
labeled as 2201, 220K and 220M in FIG. 30) are inner zone heaters located
midway between adjacent
vertices of inner hexagon 204.
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Exactly one-third of the area enclosed by respective immediate-neighboring-
region circles
centered at 'outer-hexagon-vertex' heaters is within outer zone 214. Thus, it
may be said that one-third of
each of these heaters 'belong' to outer zone 214, and two-thirds of each of
these heaters 'belong' to the
region outside of outer zone 214 (i.e. not enclosed by outer zone perimeter
208).
Exactly one-half of the area enclosed by respective immediate-neighboring-
region circles centered
at 'outer-hexagon-mid-side' heaters is within outer zone 214. Thus, it may be
said that one-half of each
of these heaters 'belong' to outer zone 214, and one-half of each of these
heaters 'belong' to the region
outside of outer zone 214 (i.e. not enclosed by outer zone perimeter 208).
Exactly one-third of the area enclosed by respective immediate-neighboring-
region circles
centered at 'inner-hexagon-vertex' heaters is within inner zone 214. Thus, it
may be said that one-third of
each of these heaters 'belong' to inner zone 210, and two-thirds of each of
these heaters 'belong' to outer
zone 214.
Exactly one-half of the area enclosed by respective immediate-neighboring-
region circles centered
at 'inner-hexagon-mid-side' heaters is within inner zone 210, and exactly one-
half of the area is within
outer zone 214. Thus, it may be said that one-half of each of these heaters
'belong' to outer zone 214, and
one-half of each of these heaters 'belong' to inner zone 210 (i.e. not
enclosed by outer zone perimeter
208).
For the heater pattern of FIG. 2A, for the purposes of computing heater
spatial density, the total
number of heaters 'belonging to' inner zone 210 include: (i) seven 'internally-
located' heaters 226
located within inner zone 210 and not on the perimeter of inner hexagon 204
(i.e. including heaters 2200
and 220P); (ii) one-half of each of the six inner zone heaters 226 located
midway between adjacent
vertices of the inner hexagon 204 (i.e. including heaters 2201, 220K and 220M)
for a total of three
heaters; and (iii) one-third of each of the six inner zone heaters 226 located
at vertices of the inner
hexagon 204 (i.e. including heaters 22011, 220J, 220L and 220N) for a total of
two heaters. Thus, a total
of 7+3+2=12 heaters belong to inner zone 210 for the purposes of computing
heater spatial density.
For the heater pattern of FIG. 2A, for the purposes of computing heater
spatial density, the total
number of heaters 'belonging to' outer zone 214 include: (i) one-half of each
of the six inner zone heaters
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226 located midway between adjacent vertices of the inner hexagon 204 (i.e.
including heaters 2201,
220K and 220M) for a total of three heaters; (ii) two-thirds of each of the
six inner zone heaters 226
located at vertices of the inner hexagon 204 (i.e. including heaters 22011,
220J, 220L and 220N) for a
total of four heaters; (iii) one-half of each of the six outer zone heaters
228 located midway between
adjacent vertices of the outer hexagon 208 (i.e. including heaters 220B, 220D
and 220F) for a total of
three heaters; and (iv) one-third of each of the six outer zone heaters 228
located at vertices of the outer
hexagon 208 (i.e. including heaters 220A, 220C, 220E and 220G) for a total of
two heaters. Thus, it may
be said that a total of 3+4+3+2=12 heaters belong to outer zone 214 for the
purposes of computing heater
spatial density.
In the example of FIG. 2A, 12 heaters belong to inner zone 210 and 12 heaters
belong to outer zone
214. Because the area of outer zone 214 is three times that of inner zone 210,
because the number of
heaters belonging to inner 210 and outer 214 zones is the same, the heater
spatial density within inner
zone 210 may be said to be three times that of outer zone 214.
In general, to compute a 'heater spatial density' of any given region (i.e.
cross section of the
subsurface), one (i) determines, for each heater in the formation within or
relatively close to the given
region, a nearest neighboring heater distance; (ii) for each heater,
determines a
'immediate-neighboring-region circle' around each heater centroid (i.e. having
a radius equal to one half
of the distance to a nearest neighboring heater), (iii) computes, for each
heater in the formation, a
fraction of the immediate-neighboring-region circle located within the given
region to determine the
fraction (i.e. between 0 and 1) of the heater belonging to the given region;
(iv) determines the total
number of heaters belonging to the given region and (v) divides this number by
the area of the given
region.
In the example of FIG.4A, exactly 16 heaters belong to inner zone 210 and
exactly 16 heaters
'belong to' outer zone 214. Thus, in the example of FIG. 4A, a ratio between
(i) a heater spatial density in
inner zone 210; and (ii) a heater spatial density in outer zone 214, is
exactly three.
In different embodiments, a spatial density ratio between a heater spatial
density in inner zone 210
and that of outer zone 214 is at least 1.5, or at least 2, or at least 2.5
and/or at most 10 or at most 7.5 or at
most 5 or at most 4.
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Some embodiments relate to a 'nearest heater' to a location in the subsurface
formation. In the
example of FIG. 31, location A 2242 (marked with a star) is closer to heater
'A' 2246 than to any other
heater. Therefore, a 'distance to a nearest heater at location A' is the
distance between location 'A' 2242
and heater 'A' 2246. In the example of FIG. 31, location B2252 (marked with a
cross) is closer to heater
'B' 256 than to any other heater. Therefore, a 'distance to a nearest heater
at location B' is the distance
between location B 2252 and heater B2256. In the example of FIG. 31, location
C2262 (marked with a
number symbol) is closer to heater 'C' 2266 than to any other heater.
Therefore, a 'distance to a nearest
heater at location C' is the distance between location C 2262 and heater C
2266.
In the example of FIG. 32, exactly two heaters are arranged so that 'Heater P'
2102 is located at point (0,1)
and 'Heater Q' 2104 is located at point (2,1). As such, all locations within
region `1(' 2106 are closer to heater 'P'
2102 than to heater 'Q' 2104, and locations within region 1' 2108 are closer
to heater 'Q' 2104 than to heater 'P'
2102. Locations on the boundary between regions `1(' 2106 and 1' 2108 are
equidistant to the heaters.
Some embodiments relate to the 'average distance' within an area of the
subsurface formation or on a
curve within the surface formation (e.g. a closed curve such as a zone
perimeter 204 or 208 or 202) to a nearest
heater. Each location within the area of curve LOGE AREA or LOGE CURVE is
associated with a distance to
a nearest heater (or heater well) ¨ this is the distance within the cross-
section of the subsurface formation for which
a heater pattern is defined to a heater centroid within the cross-section (see
FIGS. 27-28). The heater which is the
'nearest heater' to the location LOGE AREA or LOGE CURVE within the area or on
the curve is not required
to be located in the 'area' AREA or curve.
Strictly speaking, an area or curve of the subsurface of formation is a locus
of points. Each given point of
the locus is associated with a respective distance value describing a distance
to a heater closest to the given point.
By averaging these values over all points in the area or on the curve it is
possible to compute an average distance,
within the area or on the curve, to a nearest heater.
FIGS. 33-36 illustrate some relatively simple examples.
FIG. 33A illustrates a (i) single heater A 2090 situated at the origin, and
(ii) Region A 2032 which is
bounded by the lines x=0, x=1, y=0, y=1. In the example of FIG. 33A, for any
point (xo,y0) within Region A 2032,
a distance to a nearest heater is the same as the distance to the origin, i.e.
V(x0 )2 + (y0)2 . In order to determine
the average distance within Region A to a nearest heater, it is possible to
compute the integral:
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il(xo )2 + (yo )2 dxdyfl I _______________________
II (X0 )2 (y0 )2 dxdy
Re gion A 4,0
r
I Area _of _Re gion _AI j i __ dxdy
(EQN 2)
y=0 x=0
1 'j 1 1
+ -NE)+ ¨ --arctanh ¨ ¨ 0.765
6 3 12 2 4
The 'average distance to a nearest heater' within Region A (i.e. in this case,
a distance to heater A 2090
5 situated at the original) may be approximated by a distance between (i) a
centroid of Region A 2032 ¨ i.e. the point
(1/2,1/2); and (ii) heater A 2090. This distance is equal to approximately
0.71.
EQN. 2 is valid for a particular region illustrated in FIG. 33A. For any
arbitrary REGION of the subsurface,
10 an entirety of which is nearer to HEATER_H than to any other heater, the
average distance to a nearest heater or
AVG_NHD (NHD is an abbreviation for 'nearest heater distance') is given by:
DIST(LOC, HEATER _H)dLOC
AVG _NHD(REGION) = REGION
I Area _of _REGION I
15 (EQN 3)
where LOC is a location within REGION, dLOC is the size (i.e. area or volume)
of an infinitesimal portion of the
subsurface formation at location LOC within REGION, and DIST(LOC,HEATER_H) is
a distance between
HEATER_H and location LOC.
In the example of FIG. 33 only a single heater is present ¨ i.e. Heater A 2090
situated at the origin. Region
B 2032 of FIG. 33B is bounded by the lines x=0, x=0.5, y=0, y=1. For the
example of FIG. 18B, EQN 2 yields
AVG_NHD((Region B)=0.59. This may be approximated by a distance between a
centroid of Region B and
Heater A 2090, or 0.56.
EQN. 3 assumes that only a single heater is present in the subsurface
formation. EQN. 3 may be
generalized for a subsurface in which a heaters 1111,112,... Hi... HNI (i.e.
for any positive integer N) are arranged at
respective locations {LOC(H/), LOC(H/), LOC(11,),
LOC(HN), j. In this situation, any location LOC within
the subsurface formation is associated with a respective nearest heater
HNEAREST (LOC) that is selected from 11/1,
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H,... HN). In the example of FIG. 32, for all locations within Region K 2106,
a nearest heater HNEAREST (LOC)
is Heater P 2102 situated at (0,1). In the example of FIG. 6, for all
locations within Region L 2108, a nearest heater
HNEAREST (LOC) is Heater Q 2104 situated at (2,1).
For location LOC within the subsurface formation, a nearest heater distance
NHD(LOC) is defined as
DIST(LOC, HNEAREST (LOC) ) - a distance between the location LOC and its
associated nearest heater HNEAREST
(LOC). Thus, EQN. 3 may be generalized as:
NHD(LOC)dLOC
AVG _NHD(REGION) = REGION
(EQN. 4).
I Area _of _REGION I
For the example of FIG. 20, four heaters are arranged in the subsurface
formation - Heater A 90 situated at
the origin, Heater B 2092 situated at (0,2), Heater C 2094 situated at (2,2)
and Heater D 2096 situated at (2,0). In
this example, it is desired to compute the average heater distance within
Region C 2036 defined by all locations
enclosed by the four lines x=0, x=2, y=0, y=2. Region C 36 may be divided into
four sub-regions Al -A4 2080,
2082, 2084, 2086. For any location LOCA/ in sub-region Al 2080, a nearest
heater HNEAREST (LOC Ai) is Heater B
2092. For any location LOCA3 in sub-region A3 2084, a nearest heater HNEAREST
(LOC A3) is Heater A 90. For any
location LOCA2 in sub-region A2 2082, a nearest heater HNEAREST (LOC A2) is
Heater C 2094. For any location
LOCA4 in sub-region A4 2060, a nearest heater HNEAREST (LOC A4) is Heater D
2096.
By symmetry, it is clear that the average distance to a nearest heater within
Region C 2036
AVG_NHD(REGION C) of FIG. 34 is identical to the average distance to a nearest
heater within Region A 2032
AVG_NHD(REGION A) of FIG. 33A, or 0.765.
For the example of FIG. 35A, five heaters are arranged in the subsurface
formation - Heater A 2090
situated at the origin, Heater B 2092 situated at (0,2), Heater C 2094
situated at (2,2), Heater D 2096 situated at
(2,0) and Heater E 2098 situated at (1,1). In this example, it is desired to
compute the average heater distance
within Region C 2036 defined by all locations enclosed by the four lines x=0,
x=2, y=0, y=2. Region C 2036 may
be divided into eight sub-regions Bl-B8 2060, 2062, 2064, 2066, 2068, 2072,
2074. For any location LOCB/ in
sub-region B1 2060, a 'nearest heater' HNEAREST (LOC B1) is Heater B 2092. For
any location LOCB2 in sub-region
B2 2062, a 'nearest heater' HNEAREST (LOC B2) is Heater E 2098. For any
location LOCB3 in sub-region B3 2064, a
'nearest heater' HNEAREST (LOC B3) is Heater E 2098. For any location LOCB4 in
sub-region B4 2066, a 'nearest
heater' HNEAREST (LOC B4) is Heater C 2094.
For any location LOCB5 in sub-region B5 2068, a nearest heater HNEAREST (LOC
B5) is Heater A 2090. For
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any location LOCB6 in sub-region B6 70, a nearest heater HNEAREST (LOC BO is
Heater E 2098. For any location
LOCB7 in sub-region B7 2072, a nearest heater HNEAREST (E0C .67) is Heater E
2098. For any location LOCB8 in
sub-region B8 2074, a nearest heater HNEAREST (LOC BO is Heater D 2096.
By symmetry, it is clear that the average distance to a nearest heater within
Region C 2036
AVG_NHD(REGION C) of FIG. 35A is identical to the average distance to a
nearest heater within Region B 2034
AVG_NHD(REGION B) of FIG. 33B, or 0.59.
In the example of FIG. 35A, there are four corner heaters and a fifth more
central heater E 2098 situated
exactly in the center of the square-shaped region. In the example of FIG. 35B,
there are also four corner heaters ¨
however, the fifth more central heater E' 98' is situated on the center of one
of the square sides rather than in the
center of the square. The heater density for both the example of 35A and of
35B is identical. However, the
'average distance to a nearest heater' in the example of FIG. 35B is about
0.68, or about 15% greater than that of
the example of FIG. 35A. This is due to the less uniform distribution of
heaters within Region C 2038 in the
example of FIG. 35B.
The aforementioned examples relate to the average distance to a nearest heater
within an area of the
sub-formation formation. It is also possible to compute the 'average distance
to a nearest heater' for any set of
points ¨ for example, along a line, or along a curve, or along the perimeter
of a polygon.
In the example of FIG. 36 (i.e. in this example, exactly one heater is
situated in the subsurface formation),
the 'average distance to a nearest heater' along the perimeter 2052 of region
A 2032 is given by:
ydy + 11(42 + ldx + 11(y)2 + ldy + f xdx
x=0 y =0
0 0
4
(EQN. 5)
1 lAx)2 + ldx + f xdx
Lo
0
1.15
2
In general, for a curve (e.g. a closed curve) C, the average distance to a
nearest heater
NHD(LOC)dLOC
AVG _NHD(ALONG _CURVE _C) = CURVE C (EQN. 6)
I Length _of _Curve _C I
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where location LOC is a location on Curve C. One example of a Curve is inner
zone or outer zone
perimeters 204, 208.
FIG. 37A illustrates fractions of inner 210 and outer 214 zones (and
perimeters 204, 208 thereof) that are
heater-displaced or heater-centroid-displaced by at most a first threshold
distance; diam1/2. Diami is the diameter
of a circle centered around each heater centroid 310. Shaded locations in FIG.
8 are those portions of
inner and outer zones which are displaced from a centroid 310 of one or more
of the heaters 210 by less
than a distance Dian/J.. In the example of FIG. 15, each shaded circle has an
area that is around 3-5% of
the area of inner zone 210.
Because a significant number of heaters are located throughout inner zone 210,
the fraction of inner
zone 210 that is shaded is significant ¨ e.g. at least 30% or at least 40% or
at least 50% or at least 60% or
at least 70% of the area of inner zone 210. Because a significant number of
heaters are located around an
entirety of inner perimeter 204, the fraction of inner perimeter 204 that is
shaded is significant ¨ e.g. at
least 30% or at least 40% or at least 50% or at least 60% or at least 70% of
the length of inner perimeter
204. In contrast, due to the much lower heater density in outer zone 210, a
much smaller fraction of
outer zone 210 is shaded.
In the example of FIG. 37B, it is shown that when the threshold distance is
increased from a first
to a second threshold distance, the portion of the outer perimeter 208 that is
heater-displaced or
'heater-centroid-displaced' by at most the second threshold distance is
significant - e.g. at least 30% or at
least 40% or at least 50% or at least 60% or at least 70% of the length of
outer perimeter 208.
In one example, the area of the circle defining locations (e.g. see the shaded
circles of FIG. 37A)
within the subsurface formation (i.e. in the plane in which a heater pattern
is defined) is exactly 5% of the
area11of inner zone 210. In this case, the radius of inner zone 210 equals
0.05 or about 12.6% (or about
A-
one-eighth) of the square root of the area of inner zone 210, where the square
root of the area of inner
zone 210 has dimensions of length.
Embodiments of the present invention relate to apparatus and methods whereby,
for a
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cross-section of the subsurface formation, and for a threshold length or
threshold distance that is equal to
one-eighth of the area of inner zone 204, (i) a significant fraction of inner
zone 210 is covered by the
shaded circles having a radius equal to the threshold distance and an area
equal to about 5% of the area of
inner zone 204; (ii) only a significantly smaller fraction of outer zone 214
is covered by the shaded
circles having a radius equal to the same threshold distance, due to the much
lower heater density. In
some embodiments, a significant fraction of the length of inner perimeter 204
is covered by shaded
circles. In some embodiments, for a second threshold distance equal to twice
the aforementioned
'threshold distance' (e.g. equal to one quarter of the square root of the area
of inner zone 210), a
'significant fraction' of the length of outer perimeter 208 is covered by
shaded circles.
In one example, it is possible to set a threshold distance or threshold length
to one-eighth of the
area of inner zone 204 so that a magnitude of an area enclosed by a circle
whose radius is the 'threshold
distance' is equal to 5% of that of the inner zone 204.
According to this threshold distance, for the heater patterns illustrated in
FIG. 5A, (i) more than
50% (for example, about 60%) of inner zone 210 is heater-displaced or 'heater-
centroid-displaced by less
than this threshold distance, and (ii) a much smaller fraction, i.e. about 15-
20% of outer zone 214 is
displaced by less than this threshold distance. For the example of FIG. 3A,
according to this threshold
distance, (i) well over two-thirds of inner zone 210 is heater-displaced or
heater-centroid displaced by
less than this threshold distance; and (ii) a much smaller fraction, about a
third, of outer zone 210 is
heater-displaced by less than this threshold distance.
In both examples, a ratio between (i) a fraction of inner zone 210 that is
heater-displaced or
heater-centroid displaced by at most the threshold distance; and (ii) a
fraction of outer zone 214 that is
heater-displaced or heater-centroid displaced by at most the threshold
distance is at least 1.2 or at least
1.25 or at least 1.3 or at least 1.4 or at least 1.5 or at least 1.6 or at
least 1.8 or at least 1.9.
In the example of FIG. 37A, about 60% of a length of inner perimeter 204 is
heater-displaced or
heater-centroid-displaced by at most this threshold distance and about 60% of
a length of outer perimeter
208 is heater-displaced or heater-centroid-displaced by at most twice this
threshold distance. In some
embodiments, over 75% of a length of inner perimeter 204 is heater-displaced
or
heater-centroid-displaced by at most this threshold distance and over 75% of a
length of outer perimeter
208 is heater-displaced or heater-centroid-displaced by at most twice this
threshold distance.
Embodiments of the present invention refer to 'control apparatus.' Control
apparatus may include
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any combination of analog or digital circuitry (e.g. current or voltage or
electrical power regulator(s) or
electronic timing circuitry) and/or computer-executable code and/or mechanical
apparatus (e.g. flow
regulator(s) or pressure regulator(s) or valve(s) or temperature regulator(s))
or any monitoring devices
(e.g. for measuring temperature or pressure) and/or other apparatus.
5
Some embodiments relate to patterns of heaters and/or production wells
and/or injection wells.
Some embodiments relate to methods of hydrocarbon fluid production and/or
methods of heating a
subsurface formation. Unless specified otherwise, any feature or combination
of feature(s) relating to
heater and/or production well locations or patterns may be provided in
combination with any method
disclosed herein even if not explicitly specified herein. Furthermore, a
number of methods are disclosed
10
within the present disclosure, each providing its own set of respective
features. Unless specified
otherwise, in some embodiments, any feature(s) of any one method may be
combined with feature(s) of
any other method, even if not explicitly specified herein.
Furthermore, any 'control apparatus' may be programmed to carry out any method
or combination
thereof disclosed herein.
15
In the description and claims of the present application, each of the
verbs, "comprise" "include"
and "have", and conjugates thereof, are used to indicate that the object or
objects of the verb are not
necessarily a complete listing of members, components, elements or parts of
the subject or subjects of the
verb.
All references cited herein (including but not limited to PCT/U513/38089 filed
on April 24, 2013
20
and US 61/729,628 filed on November 25, 2012) are each incorporated by
reference in their entirety.
Citation of a reference does not constitute an admission that the reference is
prior art.
The articles "a" and "an" are used herein to refer to one or to more than one.
(i.e, to at least one) of
the grammatical object of the article. By way of example, "an element" means
one element or more than
one element.
25
The term "including" is used herein to mean, and is used interchangeably
with, the phrase
"including but not limited" to.
The term "or" is used herein to mean, and is used interchangeably with, the
term "and/or," unless
context clearly indicates otherwise.
The term "such as" is used herein to mean, and is used interchangeably, with
the phrase "such as
30 but not limited to".
The present invention has been described using detailed descriptions of
embodiments thereof that
are provided by way of example and are not intended to limit the scope of the
invention. The described
embodiments comprise different features, not all of which are required in all
embodiments of the
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invention. Some embodiments of the present invention utilize only some of the
features or possible
combinations of the features. Variations of embodiments of the present
invention that are described and
embodiments of the present invention comprising different combinations of
features noted in the
described embodiments will occur to persons skilled in the art.
