Note: Descriptions are shown in the official language in which they were submitted.
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SOLVENT ADDITION TO IMPROVE EFFICIENCY OF HYDROCARBON
PRODUCTION
FIELD
[0001] The present disclosure relates to recovery of hydrocarbons from
hydrocarbon-
containing reservoirs, and the use of solvents to improve efficiencies of such
recovery.
BACKGROUND
[0002] Steam-Assisted Gravity Drainage (SAGD) is an enhanced oil recovery
technology for
producing heavy crude oil and bitumen. However, in spite of its success in
recovering highly
viscous bitumen, SAGD remains an expensive technique that requires large
energy input in the
form of steam for each barrel of produced oil. This entails consuming large
quantities of water
and natural gas, resulting in considerable greenhouse gas emissions and costly
post-production
water treatment procedures.
[0003] Many modifications to SAGD continue to evolve to achieve higher
energy efficiency
and environmental sustainability while maintaining economic viability. Such
efforts include the
use of solvents along with steam to reduce bitumen viscosity simultaneously
through thermal
diffusion and dilution. However, many of these techniques still suffer from
poor efficiencies due
to, for example, the use of excessive amounts of solvent, the need to use
excessive amounts of
steam, losses of solvent, failure to produce a suitable steam to oil ratio,
the high cost of solvents,
etc. Thus, methods to improve SAGD efficiency are sought after in the
industry.
SUMMARY
[0004] In one aspect, there is provided a process for producing bitumen
from an oil sands
reservoir through a production well that is disposed in fluid communication
with an injection
well via an interwell region, comprising: supplying a production-initiating
fluid into the oil sands
reservoir via the injection well for effecting mobilization of bitumen within
the oil sands
reservoir such that the mobilized bitumen is conducted through the interwell
region to the
production well; wherein the production-initiating fluid includes steam and a
production phase
solvent, and the production phase solvent includes heavy hydrocarbon material
and light
hydrocarbon material; and wherein the heavy hydrocarbon material includes one
or more heavy
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hydrocarbons, wherein each one of the one or more heavier hydrocarbons,
independently, is a
hydrocarbon that includes a total number of carbons five (5) or more; and
wherein the light
hydrocarbon material includes one or more light hydrocarbons, wherein each one
of the one or
more light hydrocarbons, independently, is a hydrocarbon that includes a total
number of carbons
of four (4) or less.
[0005] In another aspect, there is provided a process for producing bitumen
from an oil sands
reservoir: establishing fluid communication between an injection well and a
production well via
an interwell region within an oil sands reservoir, including: supplying a
start-up phase fluid into
the oil sands reservoir via the injection well such that thermal communication
between the start-
up phase fluid and the bitumen within the interwell region is effected;
wherein the start-up phase
fluid includes steam and a start-up phase solvent, and the start-up phase
solvent includes heavy
hydrocarbon material and light hydrocarbon material; and wherein the heavy
hydrocarbon
material includes one or more heavy hydrocarbons, wherein each one of the one
or more heavy
hydrocarbons, independently, is a hydrocarbon that includes a total number of
carbons of five (5)
or more; and wherein the light hydrocarbon material includes one or more light
hydrocarbons,
wherein each one of the one or more light hydrocarbons, independently, is a
hydrocarbon that
includes a total number of carbons of four (4) or less; and after the fluid
communication has been
established, producing bitumen from the oil sands reservoir via the production
well.
[0006] In another aspect, there is provided a process for producing bitumen
from an oil sands
reservoir through a production well that is disposed in fluid communication
with an injection
well via an interwell region, comprising: selecting a production-initiating
fluid, including steam
and a production phase solvent, such that the production phase solvent is
disposed, or
substantially disposed, in a vapour state when supplied to the oil sands
reservoir, wherein the
selection is based upon information embodied in a multicomponent phase diagram
for the
components of the production-initiating fluid; and supplying the production-
initiating fluid into
the oil sands reservoir via the injection well for effecting mobilization of
bitumen within the oil
sands reservoir such that the mobilized bitumen is conducted through the
interwell region to the
production well.
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[0007] In another aspect, there is provided a process for producing bitumen
from an oil sands
reservoir through a production well that is disposed in fluid communication
with an injection
well via an interwell region, comprising: establishing fluid communication
between an injection
well and a production well via an interwell region within an oil sands
reservoir, wherein the
establishing includes: selecting a start-up phase fluid composition, including
steam and a start-up
phase solvent, such that the start-up phase solvent is disposed, or
substantially disposed, in a
vapour state when supplied to the oil sands reservoir, wherein the selection
is based upon
information embodied in a multicomponent phase diagram for the components of
the start-up
phase fluid; and supplying the start-up phase fluid into the oil sands
reservoir via the injection
well or the production well such that the start-up phase fluid becomes
disposed in thermal
communication with bitumen within the oil sands reservoir for effecting
mobilization of bitumen
within the oil sands reservoir; and after the fluid communication has been
established, producing
bitumen from the oil sands reservoir via the production well.
[0008] In another aspect, there is provided a process for producing bitumen
from an oil sands
reservoir through a production well that is disposed in fluid communication
with an injection
well via an interwell region, comprising: during a SAGD production phase,
supplying a
production-initiating fluid to the oil sands reservoir via the injection well
such that mobilization
of bitumen within the oil sands reservoir is effected, and such that the
mobilized bitumen is
conducted to the production well and produced via the production well, wherein
the production-
initiating fluid includes steam and solvent that includes hydrocarbon
material; suspending the
supplying of the production-initiating fluid to the oil sands reservoir via
the injection well,
wherein, prior to the suspension of the production-initiating fluid to the oil
sands reservoir via
the injection well, and while the production-initiating fluid is being
supplied to the oil sands
reservoir via the injection well, the reservoir is disposed at a pre-SAGD
production phase
suspension pressure; after the supplying of the production-initiating fluid to
the oil sands
reservoir via the injection well has been suspended, and after the pressure
within the oil sands
reservoir has been reduced from a pre-SAGD production phase suspension
pressure, and while
the oil sands reservoir is being vented via at least one of the injection well
and the production
well, collecting gaseous material that is being conducted via the at least one
of the injection well
and the production well such that at least some of the supplied solvent is
recovered.
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[0009] In another aspect, there is provided a process for producing bitumen
from an oil sands
reservoir through a production well that is disposed in fluid communication
with an injection
well via an interwell region, comprising: establishing fluid communication,
through the interwell
region, between the injection well and the production well, wherein the
establishing fluid
communication includes supplying a start-up phase fluid via the injection well
or the production
well such that thermal communication between the start-up phase fluid and the
bitumen within
the interwell region is effected, wherein the start-up phase fluid includes
steam; after the fluid
communication has been established, during a SAGD production phase, supplying
a production-
initiating fluid to the oil sands reservoir via the injection well such that
mobilization of bitumen
within the oil sands reservoir is effected, and such that the mobilized
bitumen is conducted to the
production well and produced via the production well, wherein the production-
initiating fluid
includes steam; wherein at least one of the start-up phase fluid and the
production-initiating fluid
includes solvent that includes hydrocarbon material; suspending the supplying
of the production-
initiating fluid to the oil sands reservoir via the injection well, wherein,
prior to the suspension of
the production-initiating fluid to the oil sands reservoir via the injection
well, and while the
production-initiating fluid is being supplied to the oil sands reservoir via
the injection well, the
reservoir is disposed at a pre-SAGD production phase suspension pressure;
after the supplying of
the production-initiating fluid to the oil sands reservoir via the injection
well has been
suspended, and after the pressure within the oil sands reservoir has been
reduced from a pre-
SAGD production phase suspension pressure, and while the oil sands reservoir
is being vented
via at least one of the injection well and the production well, collecting
gaseous material that is
being conducted via the at least one of the injection well and the production
well such as at least
some of the supplied solvent is recovered.
[0010] In another aspect, there is provided a process for producing bitumen
from an oil sands
reservoir: establishing fluid communication between an injection well and a
production well via
an interwell region within an oil sands reservoir, including: supplying a
start-up phase fluid into
the oil sands reservoir via the injection well such that thermal communication
between the start-
up phase fluid and the bitumen within the interwell region is effected,
wherein the start-up phase
fluid includes steam and a start-up phase solvent, and after the fluid
communication has been
established, producing bitumen from the oil sands reservoir via the production
well.
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[0011] In another aspect, there is provided a process for producing bitumen
from an oil sands
reservoir through a production well that is disposed in fluid communication
with an injection
well via an interwell region, comprising: during a first stage of the SAGD
production phase,
supplying a first production-initiating fluid into the oil sands reservoir via
the injection well for
effecting mobilization of bitumen within the oil sands reservoir such that the
mobilized bitumen
is conducted through the interwell region to the production well, wherein the
first production-
initiating fluid includes steam and a production phase solvent consisting of
one or more
production phase solvent hydrocarbons; suspending the supplying of the first
production
initiating fluid; and after the suspending of the supplying of the first
production initiating fluid,
during a second stage of the SAGD production phase, supplying a second
production initiating
fluid is injected into the injection well for effecting mobilization of
bitumen within the oil sands
reservoir such that a second mobilized bitumen is conducted through the
interwell region to the
production well, wherein the second production initiating fluid includes steam
and a production
phase solvent consisting of one or more production phase solvent hydrocarbons;
wherein the
ratio of moles of start-up phase solvent to steam within the start-up phase
fluid is greater than
the ratio of moles of production phase solvent to steam within the first
production initiating fluid,
and the ratio of moles of production phase solvent to steam is greater within
the first production
initiating fluid relative to that within the second production initiating
fluid.
[0012] In another aspect, there is provided a process for producing bitumen
from an oil sands
reservoir through a production well that is disposed in fluid communication
with an injection
well via an interwell region, comprising: during a first stage of the SAGD
production phase,
supplying a first production-initiating fluid into the oil sands reservoir via
the injection well for
effecting mobilization of bitumen within the oil sands reservoir such that the
mobilized bitumen
is conducted through the interwell region to the production well, wherein the
first production-
initiating fluid includes steam and a production phase solvent consisting of
one or more
production phase solvent hydrocarbons; suspending the supplying of the first
production
initiating fluid; and after the suspending of the supplying of the first
production initiating fluid,
during a second stage of the SAGD production phase, supplying a second
production initiating
fluid is injected into the injection well for effecting mobilization of
bitumen within the oil sands
reservoir such that a second mobilized bitumen is conducted through the
interwell region to the
production well, wherein the second production initiating fluid includes steam
and a production
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phase solvent consisting of one or more production phase solvent hydrocarbons;
wherein at least
70 mol % of the production phase solvent, of the first production initiating
fluid, consists of
heavy hydrocarbon material, based on the total number of moles of the
production phase solvent
being injected, and less than 35 mol % of the production phase solvent, of the
second production-
initiating fluid, consists of light hydrocarbon material, based on the total
number moles of the
production phase solvent being injected, wherein the production phase solvent
of the first
production-initiating fluid has a higher molar concentration of heavy
hydrocarbon material than
the production phase solvent of the second production-initiating fluid.
BRIEF DESCRIPTION OF DRAWINGS
[0013] The preferred embodiments will now be described with the following
accompanying
drawings, in which:
[0014] Figure 1 is a schematic illustration of a system including an
injection well and a
production well within an oil sands reservoir for carrying out a SAGD process;
[0015] Figure 2 is a schematic illustration of the phase during SAGD
production when the
steam chamber has grown such that the steam chamber has reached the cap rock;
and
[0016] Figure 3 is table illustrating the composition of an embodiment of a
solvent.
DETAILED DESCRIPTION
[0017] The present disclosure relates to the use of solvents during the
start-up phase of a
steam-assisted gravity drainage ("SAGD") operation, as well as the use of
solvents during the
production phase of a SAGD operation.
[0018] As used herein, the following terms have the following meanings:
[0019] "Hydrocarbon" is an organic compound consisting primarily of
hydrogen and carbon,
and, in some instances, may also contain heteroatoms such as sulfur, nitrogen
and oxygen.
[0020] "Hydrocarbon material" is material that consists of one or more
hydrocarbons.
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[0021] "Heavy hydrocarbon" is a hydrocarbon having a total number of carbon
atoms of five
(5) or more.
[0022] "Heavy hydrocarbon material" is a material that consists of one or
more heavy
hydrocarbons.
[0023] "Light hydrocarbon" is a hydrocarbon having a total number of carbon
atoms of four
(4) or less.
[0024] "Light hydrocarbon material" is material that consists of one or
more light
hydrocarbons.
[0025] Referring to Figure 1, there is provided a system 100 for carrying
out a process for
producing a hydrocarbon from a hydrocarbon-containing reservoir 102. In some
embodiments,
for example, the hydrocarbon-containing reservoir is an oil sands reservoir,
and the hydrocarbons
includes heavy oil, such as bitumen.
[0026] The system 100 includes a pair of wells 104, 106. An interwell
region 108, of the
reservoir 102, is disposed between the wells 104, 106.
[0027] In a SAGD operation, each one of the wells 104, 106 includes a
horizontal portion,
and the horizontal portions are vertically spaced from one another, such that
the horizontal
portion of the well 104 is vertically higher than the well 106. During the
production phase a
SAGD operation, the well 104 functions to inject a production-initiating fluid
116 (such as
steam, or a fluid including steam) into the reservoir 102, and thereby
mobilize the hydrocarbons
(the "reservoir hydrocarbons") within the interwell region 108. Upon
mobilization, the bitumen
is conducted to the horizontal portion of the well 106 by gravity drainage
through a steam
chamber (that has been established earlier during a start-up phase of SAGD, by
circulation of the
steam within one or both of the wells 104, 106: see below). In parallel,
during the production
phase of the SAGD operation, the well 106 functions to receive the mobilized
reservoir
hydrocarbons, as well as some of the condensed water, (which has also drained
by gravity to the
well 106 though the established steam chamber) and produce a production fluid
112, including
the received reservoir hydrocarbons and the condensed water. In this respect,
the well 104 may
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be referred to as the injection well 104, and the well 106 may be referred to
as the production
well 106.
[0028] The production fluid may subsequently be conducted to a processing
facility 110. At
the processing facility 110, various processing operations can occur but
generally, the water and
the reservoir hydrocarbons can be separated, with the reservoir hydrocarbons
114 sent on for
further refining. Water from the separation may be recycled to a steam
generation unit within the
facility 110, with or without further treatment, and used to generate the
steam used for supply to
the well 104.
[0029] The production phase of a SAGD operation is able to occur when fluid
communication between the wells 104, 106, within the interwell region 108, has
been
established. In some embodiments, for example, initially, the reservoir 102
has relatively low
fluid mobility. In order to enable the injected production-initiating fluid
116 (being injected
through the injection well 104) to promote the conduction of the reservoir
hydrocarbons, within
the reservoir 102, to the production well 106, fluid communication must be
established within
the interwell region 108 between the wells 104, 106. The fluid communication
may be
established during a "start-up" phase of the SAGD operation. During the start-
up phase, the
interwell region 108 is heated. The heat that is supplied to the interwell
region 108 effects
mobilization of the reservoir hydrocarbons within the interwell region 108 by
reducing the
viscosity of the reservoir hydrocarbons. The mobilized bitumen drains to the
production well
106, resulting in the creation of a fluid passage, for enabling the locally
entrained reservoir
hydrocarbons, including bitumen, to escape the interwell region 108. As more
bitumen is
mobilized and drains to the production well 106, the fluid passage grows and
eventually effects
fluid communication between the injection well 104 and the production well
106. In some
embodiments, for example, the heat is supplied to the interwell region 108 by
circulating a start-
up phase fluid 118 (such as steam, or a fluid including steam) through one or
both of the wells
104, 106.
[0030] The production phase includes ramp-up. plateau and wind-down. During
ramp-up,
bitumen production rates are still increasing. During plateau, the rates have
peaked and remain
stable or decline slowly. During wind-down, the rates are declining.
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[0031] Solvent may be added during the start-up phase of SAGD, during the
production
phase of SAGD, or both. In this context, the term "solvent" is intended to
refer to material that,
when disposed in the liquid state, is able to, at least to some extent,
dissolve in bitumen.
(A) Solvent Addition During Start-Up Phase of SAGD Operation
[0032] In some embodiments, for example, the addition of solvent during the
start-up phase
of a SAGD operation (i.e. prior to establishment, or substantial
establishment, of interwell fluid
communication) accelerates the mobilization of bitumen in the interwell
region, and promotes
the rapid formation of a steam chamber. The ability to establish good
interwell communication
during the start-up phase in turn allows the subsequent phases of the SAGD
operation to perform
more effectively. Once good communication is established, there is continued
development and
growth of the steam chamber, and the entirety of the SAGD operation is
enhanced. Establishing
good communication early on in a SAGD operation allows for much better ramp-up
and much
better overall SAGD performance. The time required to switch between the start-
up phase of a
SAGD operation to the ramp-up phase of a SAGD-mode of operation is diminished
when solvent
is added during the start-up phase of a SAGD operation. The more rapid and/or
enhanced
mobilization of bitumen is due to the combined effects of conduction,
convective heating and
dilution by solvent on viscosity of the bitumen in the inter-well zone, and
all of these effects are
particularly pronounced when solvent is added early in a SAGD operation.
[0033] In this respect, in some embodiments, for example, during the start-
up phase of a
SAGD operation, a start-up phase fluid 118 is supplied via either one of the
injection well 104
and the production well 106, such as by circulation within the respective
well, such that thermal
communication is effected between the start-up phase fluid 118 and the bitumen
within the
interwell region disposed between the injection well 104 and the production
well 106. The
effected thermal communication is such that the bitumen within the interwell
region is
mobilized. The mobilized bitumen drains to the production well 106, resulting
in the creation of
a fluid passage, for enabling the locally entrained reservoir hydrocarbons,
including bitumen, to
escape the interwell region 108. As more bitumen is mobilized and drains to
the production well
106, the fluid passage grows and eventually effects fluid communication
between the injection
well 104 and the production well 106.
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[0034] The start-up phase fluid includes steam and a start-up phase
solvent. In this respect,
in some embodiments, for example, the start-up phase solvent is co-injected
with the steam.
[0035] The start-up phase solvent consists of one or more start-up phase
solvent
hydrocarbons. A variety of hydrocarbons can be used. In some embodiments, for
example, the
hydrocarbon is chosen based on miscibility in bitumen, availability, cost and
thermo-physical
properties.
[0036] The function of the start-up phase solvent hydrocarbons includes,
amongst other
things, is to dissolve into the reservoir hydrocarbons, and effect a reduction
in viscosity of the
reservoir hydrocarbons.
[0037] In some embodiments, for example, the start-up phase fluid may
include between 0.1
and 30 mol % (such as, for example, between 3 and 30 mol %) of the start-up
phase solvent,
based on the total number of moles of the start-up phase fluid. The total
amount of start-up
phase solvent used is based on oil viscosity at initial conditions, operating
pressure, the
formation permeability and the composition of the start-up phase solvent.
[0038] The start-up phase solvent may be recovered from the produced
production fluid in
the facility 110 and re-used for injection into the oil sands reservoir. In
some embodiments, for
example, it is useful to use start-up phase solvent which is an on-site
diluent as this can reduce
blending requirements for facilitating transport, by pipeline, to a refinery.
[0039] The start-up phase solvent may be a single or multi-component fluid.
Multi-
component production phase solvent allow for operational flexibility, as the
functionality of the
solvent may be preserved over a wider range of operating conditions. In some
embodiments, for
example, the one or more start-up phase solvent hydrocarbons may include a
hydrocarbon having
a total number of 1 to 30 carbon atoms. In this respect, in some embodiments,
for example, the
one or more start-up phase solvent hydrocarbons may include heavy hydrocarbons
and/or light
hydrocarbons. Exemplary hydrocarbons include aromatics, xylene, hexane,
gasoline, kersosene,
naphtha, gas condensates, diesel, benzene, toluene, distallates, butane,
methane, and pentane.
[0040] An example of a multi-component start-up phase solvent that may be
used is cracked
naphtha. "Cracked naphtha" generally refers to naphthas that come from
refinery processes such
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as catalytic or thermal cracking or visbreaking. There are a number of
suitable cracked naphtha
compositions.
[0041] Another suitable multi-component start-up phase solvent is natural
gas condensate.
Natural gas condensate may have a variety of compositions depending on the
source, but
generally has a specific gravity ranging from 0.5 to 0.8 and is composed of
hydrocarbons such as
propane, butane, pentane, hexane, etc. Gas condensate generally has very low
viscosity and is
frequently used as a diluent to dilute heavier oils to meet pipeline
specifications.
[0042] Some of the benefits of injection of a mixture of steam and the
start-up phase solvent
during the start-up phase of a SAGD operation includes:
= oil production rates are accelerated and the SOR is reduced;
= solvent injection with steam improves the dehydration of produced
emulsions and post-
production water handling;
= when solvents having higher molecular weight hydrocarbons, such as gas
condensate, are
used, the amount of asphaltene precipitation is minimized;
= solvent recovery is improved;
= steam chamber growth rate is faster when solvent is added during the
start-up phase of
SAGD, allowing the optimization of the later stages of a SAGD operation; and
= starting solvent injection earlier extends the solvent-bitumen contact
time and
consequently increases the solvent penetration depth into the bitumen.
(B) Solvent Addition During the Production Phase of a SAGD Operation
[00431 During the production phase of the SAGD operation, in parallel with
the injection of
steam into the reservoir 102, production phase solvent may also be injected
into the reservoir
102. In some embodiments, for example, a production-initiating fluid 116 may
be injected into
the reservoir 102, the production-initiating fluid including a mixture of
steam and the production
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phase solvent, hi this respect, in some embodiments, for example, the
production phase solvent
is co-injected with the steam through the injection well 104.
[0044] By injecting production phase solvent, and thereby supplementing the
injected steam,
mobilization of the reservoir hydrocarbons, and their drainage to the
production well 106, is
accelerated.
[0045] Once disposed within the reservoir, the injected steam condenses
within the steam
chamber that has been developed within the reservoir 102, thereby transferring
its latent heat to
the reservoir 102, resulting in heating of the reservoir hydrocarbons, with a
concomitant
reduction in their viscosity. In parallel, the injected production phase
solvent, in gaseous form,
upon becoming disposed within the reservoir, also condenses within the
reservoir 102 at the
boundary of the steam chamber, liberating further heat to the reservoir 102
and thereby heating
the reservoir hydrocarbons. The condensed production phase solvent also
dissolves into the
reservoir hydrocarbons and, in this respect, in conjunction with the heat
received from the steam,
decreases the viscosity, and thereby further increasing the mobility of the
reservoir
hydrocarbons. As the reservoir hydrocarbons drain, a new interface emerges for
interaction with
the steam and the production phase solvent. In this respect, with the
supplementary production
phase solvent injection, hydrocarbon recovery may be increased, and cumulative
steam-to-oil
ratio ("SOR") may be reduced, relative to the production phase of a SAGD
operation without
any solvent injection.
[0046] The use of production phase solvent, in conjunction with steam,
during the production
phase of a SAGD operation, may also enable more uniform conduction of
mobilized
hydrocarbons along the length of the wells 104, 106. This is because the
provision of the
production phase solvent, in those well segments that are being heated to
lower temperatures,
compensates for these local "cold spots", by enabling mobilization of the
reservoir hydrocarbons,
notwithstanding the lower temperatures in these segments. This is due to the
fact that, generally,
solvents have greater solubility at lower temperatures. Accordingly, in cold
spots, more solvent
will be dissolved, partly compensating for the higher oil viscosity caused by
the lower
temperature.
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[0047] The production phase solvent consists of one or more production
phase solvent
hydrocarbons. A variety of hydrocarbons can be used. In some embodiments, for
example, the
hydrocarbon is chosen based on miscibility in bitumen, availability, cost and
thermo-physical
properties.
[0048] The function of the production phase solvent hydrocarbons includes,
amongst other
things, to dissolve into the reservoir hydrocarbons, and effect a reduction in
viscosity of the
reservoir hydrocarbons.
[0049] In some embodiments, for example, the production-initiating fluid
may include
between 0.1 and 30 mol % (such as, for example, between 3 and 30 mol %) of
production phase
solvent, based on the total moles of the production-initiating fluid. The
total amount of
production phase solvent used is based on oil viscosity at initial conditions,
operating pressure,
the formation permeability and the composition of the production phase
solvent.
[0050] The ratio of the vapor pressure of the production phase solvent at
steam temperature
to the total pressure of the system determines the maximum amount of the
production phase
solvent that can be kept in the vapor phase within the steam chamber at
specific SAGD operating
conditions. This ratio also represents the maximum amount of production phase
solvent that
should be used, as using additional production phase solvent may not result in
additional
benefits. Viewed another way, once the bitumen becomes saturated with
production phase
solvent, there are only small incremental improvements that may come from
injecting additional
production phase solvent into the reservoir. Also, due to increasing partial
pressure of the
solvent in the vapour phase, as solvent concentration increases, there will be
a greater tendency
for solvent to condense into the liquid phase such that its conduction to the
edge of the vapour
chamber is curtailed.
[0051] The production phase solvent may be recovered from the produced
production fluid
in the facility 110 and re-used for injection into the oil sands reservoir. In
some embodiments,
for example, it is useful to use production phase solvent which is an on-site
diluent as this can
reduce blending requirements for facilitating transport, by pipeline, to a
refinery.
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[0052] The production phase solvent can be a single or multi-component
fluid. Multi-
component production phase solvents allow for operational flexibility, as the
functionality of the
solvent may be preserved over a wider range of operating conditions. In some
embodiments, for
example, the one or more production phase solvent hydrocarbons may include a
hydrocarbon
having a total number of 1 to 30 carbon atoms. In this respect, in some
embodiments, for
example, the one or more production phase solvent hydrocarbons may include
heavy
hydrocarbons and/or light hydrocarbons. Exemplary hydrocarbons include
aromatics, xylene,
hexane, gasoline, kersosene, naphtha, gas condensates, diesel, benzene,
toluene, distallates,
butane, methane, and pentane.
[0053] An example of a multi-component production phase solvent that may be
used is
cracked naphtha. "Cracked naphtha" generally refers to naphthas that come from
refinery
processes such as catalytic or thermal cracking or visbreaking. There are a
number of suitable
cracked naphtha compositions.
[0054] Another suitable multi-component production phase solvent is natural
gas condensate.
Natural gas condensate may have a variety of compositions depending on the
source, but
generally has a specific gravity ranging from 0.5 to 0.8 and is composed of
hydrocarbons such as
propane, butane, pentane, hexane, etc. Gas condensate generally has very low
viscosity and is
frequently used as a diluent to dilute heavier oils to meet pipeline
specifications.
Reducing solvent content being added in a later stage of the SAGD production
phase
100551 In some embodiments, for example, it may be suitable to reduce the
amount of
production phase solvent being injected during later stages of the production
phase of a SAGD
operation. In this way, less residual solvent may remain within the oil sands
reservoir after
completion of SAGD.
[0056] In this respect, in some embodiments, for example, a process for
producing bitumen
from an oil sands reservoir through a production well 106 that is disposed in
fluid
communication with an injection well 104 via an interwell region 108 is
provided. The process
includes, during a first stage of the SAGD production phase, injecting a first
production
initiating fluid into the injection well 104 for conducting of the injected
production initiating
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fluid to the oil sands reservoir for effecting mobilization of bitumen within
the oil sands reservoir
such that a first mobilized bitumen is conducted through the interwell region
108 to the
production well 106. The first production initiating fluid includes steam and
a production phase
solvent, the production phase solvent consisting of one or more production
phase solvent
hydrocarbons. The first mobilized bitumen is recovered through the production
well 106.
Subsequently, the injecting of the first production initiating fluid is
suspended, such that the first
stage of the SAGD production phase is completed. After completion of the first
stage of the
SAGD production phase, the second stage of the SAGD production phase is
effected (i.e. the
first stage is an earlier stage, and the second stage is a later stage).
During the second stage of
the SAGD production phase, a second production initiating fluid is injected
into the injection
well 104 for conducting of the injected production initiating fluid to the oil
sands reservoir for
effecting mobilization of bitumen within the oil sands reservoir such that a
second mobilized
bitumen is conducted through the interwell region 108 to the production well
106. The second
production initiating fluid includes steam and a production phase solvent, the
production phase
solvent consisting of one or more production phase solvent hydrocarbons. The
second mobilized
bitumen is recovered through the production well 106. Subsequently, the
injecting of the second
production initiating fluid is suspended, such that the second stage of the
SAGD production
phase is completed. The ratio of moles of production phase solvent to steam is
greater (such as,
for example, 10% greater, such as, for example, 25% greater, such as, for
example, 50% greater)
within the first production initiating fluid relative to that within the
second production initiating
fluid. The ratio of moles of production phase solvent to steam is greater
(such as, for example,
10% greater, such as, for example, 25% greater, such as, for example, 50%
greater) within the
second production initiating fluid relative to that within the third
production initiating fluid. In
some embodiments, for example, the rate of production of bitumen, via the
production well,
during the first stage of the SAGD production phase is greater than the rate
of production of
bitumen, via the production well, during the second stage of the SAGD
production phase, such
as, for example, by at least 25%, such as, for example, by at least 50%, such
as, for example, by
at least 100%. In some embodiments, for example, the first stage of the SAGD
production phase
occurs prior to the steam chamber reaching the cap rock 300 (see Figure 2),
and the second stage
of the SAGD production phase occurs after the steam chamber has reached the
cap rock 300. In
some embodiments, for example, the first stage may include at least a portion
of a "steam
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chamber initialization" phase, at least a portion of a "plateau phase", or at
least portions of both.
In some embodiments, for example, the second stage may include a "lateral
growth only" phase,
a "winding down" phase, or at least portions of both.
(ii)
Transitioning from heavier to lighter solvents in later stages of the SAGD
production
phase
[0057] In
some embodiments, for example, it may be suitable to transition from a heavier
production phase solvent to a lighter production phase solvent at some point
in time during the
production phase of a SAGD operation. In some embodiments, for example, at
some point in
time during the production phase of a SAGD operation, a heavier production
phase solvent may,
relative to a lighter production phase solvent, have a greater tendency to
condense prior to
reaching the interface between the bitumen, that is entrained within the oil
sands reservoir, and
the steam chamber, and thereby fail to mobilize the bitumen. This may dictate
the switching
over to a lighter production phase solvent, in order to improve efficiencies
in mobilizing bitumen
within the oil sands reservoir.
[0058] In
one respect, in some embodiments, for example, there is provided a process for
producing bitumen from an oil sands reservoir through a production well 106
that is disposed in
fluid communication with an injection well 104 via an interwell region 108.
The process
includes, during a first stage of the SAGD production phase, injecting a first
production initiating
fluid into the injection well 104 for conducting of the injected first
production initiating fluid to
the oil sands reservoir for effecting mobilization of bitumen within the oil
sands reservoir such
that a first mobilized bitumen is conducted through the interwell region 108
to the production
well 106, wherein the first production initiating fluid includes steam and a
production phase
solvent, the production phase solvent consisting of one or more production
phase solvent
hydrocarbons. The first mobilized bitumen is recovered through the production
well 106.
Subsequently, the injecting of the first production initiating fluid is
suspended, such that the first
stage of the SAGD production phase is completed. After completion of the first
stage of the
SAGD production phase, the second stage of the SAGD production phase is
effected. During the
second stage of the SAGD production phase, a second production initiating
fluid is injected into
the injection well 104 for conducting of the injected second production
initiating fluid to the oil
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sands reservoir for effecting mobilization of bitumen within the oil sands
reservoir such that a
second mobilized bitumen is conducted through the interwell region 108 to the
production well
106, wherein the second production initiating fluid includes steam and a
production phase
solvent, the production phase solvent consisting of one or more production
phase solvent
hydrocarbons. The second mobilized bitumen is recovered through the production
well 106.
The density of the production phase solvent is greater within the first
production initiating fluid
relative to that within the second production initiating fluid. In some
embodiments, for example,
the density of the production phase solvent is at least 10% (such as, for
example, at least 20%,
such as, for example, at least 30%) greater within the first production
initiating fluid relative to,
the density of the production phase solvent within the second production
initiating fluid. In some
embodiments, for example, at least 70 mol % (such as, for example, at least 80
mol %, such as,
for example, at least 90 mol %) of the production phase solvent, of the first
production initiating
fluid, consists of heavy hydrocarbon material, based on the total number of
moles of the
production phase solvent being injected, and less than 35 mol % (such as, for
example, less than
25 mol %, such as, for example, less than 15 mol %) of the production phase
solvent, of the
second production-initiating fluid, consists of light hydrocarbon material,
based on the total
number moles of the production phase solvent being injected, wherein the
production phase
solvent of the first production-initiating fluid has a higher molar
concentration of heavy
hydrocarbon material than the production phase solvent of the second
production-initiating fluid.
In some embodiments, for example, the vapour pressure of the second production
initiating fluid
is greater than the vapour pressure of the first production initiating fluid,
such as, for example, by
at least 10%, such as, for example, by at least 20%, such as, for example, by
at least 30%. In
some embodiments, for example, the rate of production of bitumen, via the
production well,
during the first stage of the SAGD production phase is greater than the rate
of production of
bitumen, via the production well, during the second stage of the SAGD
production phase, such
as, for example, by at least 25%, such as, for example, by at least 50%, such
as, for example, by
at least 100%. In some embodiments, for example, the first stage of the SAGD
production phase
occurs prior to the steam chamber reaching the cap rock 300 (see Figure 2),
and the second stage
of the SAGD production phase occurs after the steam chamber has reached the
cap rock 300. In
some embodiments, for example, the first stage may include at least a portion
of a "steam
chamber initialization" phase, at least a portion of a "plateau phase", or at
least portions of both.
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In some embodiments, for example, the second stage may include a "lateral
growth only" phase,
a "winding down" phase, or at least portions of both.
[0059] In another respect, in some embodiments, for example, there is
provided a process for
producing bitumen from an oil sands reservoir through a production well 106
that is disposed in
fluid communication with an injection well 104 via an interwell region 108.
The process
includes, during a first stage of the SAGD production phase, injecting a first
production initiating
fluid into the injection well 104 for conducting of the injected first
production initiating fluid to
the oil sands reservoir for effecting mobilization of bitumen within the oil
sands reservoir such
that a first mobilized bitumen is conducted through the interwell region 108
to the production
well 106, wherein the first production initiating fluid includes steam and a
production phase
solvent, the production phase solvent consisting of one or more production
phase solvent
hydrocarbons. The first mobilized bitumen is recovered through the production
well 106.
Subsequently, the injecting of the first production initiating fluid is
suspended, such that the first
stage of the SAGD production phase is completed. After completion of the first
stage of the
SAGD production phase, the second stage of the SAGD production phase is
effected. During the
second stage of the SAGD production phase, a second production initiating
fluid is injected into
the injection well 104 for conducting of the injected second production
initiating fluid to the oil
sands reservoir for effecting mobilization of bitumen within the oil sands
reservoir such that a
second mobilized bitumen is conducted through the interwell region 108 to the
production well
106, wherein the second production initiating fluid includes steam and a
production phase
solvent, the production phase solvent consisting of one or more production
phase solvent
hydrocarbons. The second mobilized bitumen is recovered through the production
well 106.
The weight average molecular weight of the production phase solvent is greater
within the first
production initiating fluid relative to that within the second production
initiating fluid. In some
embodiments, for example, the weight average molecular weight of the
production phase solvent
is at least 10% (such as, for example, at least 20%, such as, for example, at
least 30%) greater
within the first production initiating fluid relative to the weight average
molecular weight of the
production phase solvent within the second production initiating fluid. In
some embodiments,
for example, at least 70 mol % (such as, for example, at least 80 mol %, such
as, for example, at
least 90 mol %) of the production phase solvent, of the first production
initiating fluid, consists
of heavy hydrocarbon material, based on the total number of moles of the
production phase
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solvent being injected, and less than 35 mol % (such as, for example, less
than 25 mol %, such
as, for example, less than 15 mol %) of the production phase solvent, of the
second production-
initiating fluid, consists of light hydrocarbon material, based on the total
number moles of the
production phase solvent being injected, wherein the production phase solvent
of the first
production-initiating fluid has a higher molar concentration of heavy
hydrocarbon material than
the production phase solvent of the second production-initiating fluid. In
some embodiments, for
example, the vapour pressure of the second production initiating fluid is
greater than the vapour
pressure of the first production initiating fluid, such as, for example, by at
least 10%, such as, for
example, by at least 20%, such as, for example, by at least 30%. In some
embodiments, for
example, the rate of production of bitumen, via the production well, during
the first stage of the
SAGD production phase is greater than the rate of production of bitumen, via
the production
well, during the second stage of the SAGD production phase, such as, for
example, by at least
25%, such as, for example, by at least 50%, such as, for example, by at least
100%. In some
embodiments, for example, the first stage of the SAGD production phase occurs
prior to the
steam chamber reaching the cap rock 300 (see Figure 2), and the second stage
of the SAGD
production phase occurs after the steam chamber has reached the cap rock 300.
In some
embodiments, for example, the first stage may include at least a portion of a
"steam chamber
initialization" phase, at least a portion of a "plateau phase", or at least
portions of both. In some
embodiments, for example, the second stage may include a "lateral growth only"
phase, a
"winding down" phase, or at least portions of both.
[0060] In another respect, in some embodiments, for example, there is
provided another
process for producing bitumen from an oil sands reservoir through a production
well 106 that is
disposed in fluid communication with an injection well 104 via an interwell
region 108. The
process includes, during a first stage of the SAGD production phase, injecting
a first production
initiating fluid into the injection well 104 for conducting of the injected
first production initiating
fluid to the oil sands reservoir for effecting mobilization of bitumen within
the oil sands reservoir
such that a first mobilized bitumen is conducted through the interwell region
108 to the
production well 106. The first production initiating fluid includes steam and
a production phase
solvent, and the production phase solvent consists of one or more production
phase solvent
hydrocarbons. The first mobilized bitumen is recovered through the production
well 106.
Subsequently, the injecting of the first production initiating fluid is
suspended, such that the first
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stage of the SAGD production phase is completed. After completion of the first
stage of the
SAGD production phase, the second stage of the SAGD production phase is
effected. During the
second stage of the SAGD production phase, a second production initiating
fluid is injected into
the injection well 104 for conducting of the injected second production
initiating fluid to the oil
sands reservoir for effecting mobilization of bitumen within the oil sands
reservoir such that a
second mobilized bitumen is conducted through the interwell region 108 to the
production well
106. The second production initiating fluid includes steam and a production
phase solvent. The
production phase solvent consists of one or more production phase solvent
hydrocarbons. The
second mobilized bitumen is recovered through the production well 106. At
least 70 mol %
(such as, for example, at least 80 mol %, such as, for example, at least 90
mol %) of the
production phase solvent, of the first production initiating fluid, consists
of heavy hydrocarbon
material, based on the total number of moles of the production phase solvent
being injected, and
less than 35 mol % (such as, for example, less than 25 mol %, such as, for
example, less than 15
mol %) of the production phase solvent, of the second production-initiating
fluid, consists of
light hydrocarbon material, based on the total number moles of the production
phase solvent
being injected, wherein the production phase solvent of the first production-
initiating fluid has a
higher molar concentration of heavy hydrocarbon material than the production
phase solvent of
the second production-initiating fluid. In some embodiments, for example, the
vapour pressure
of the second production initiating fluid is greater than the vapour pressure
of the first production
initiating fluid. In some of these embodiments, for example, the vapour
pressure of the second
production initiating fluid is greater than the vapour pressure of the first
production initiating
fluid by at least 10%. In some embodiments, for example, the rate of
production of bitumen, via
the production well, during the first stage of the SAGD production phase is
greater than the rate
of production of bitumen, via the production well, during the second stage of
the SAGD
production phase, such as, for example, by at least 25%, such as, for example,
by at least 50%,
such as, for example, by at least 100%. In some embodiments, for example, the
first stage of the
SAGD production phase occurs prior to the steam chamber reaching the cap rock
300 (see Figure
2), and the second stage of the SAGD production phase occurs after the steam
chamber has
reached the cap rock 300. In some embodiments, for example, the first stage
may include at least
a portion of a "steam chamber initialization" phase, at least a portion of a
"plateau phase", or at
CA 02952864 2016-12-16
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least portions of both. In some embodiments, for example, the second stage may
include a
"lateral growth only" phase, a "winding down" phase, or at least portions of
both.
(C)
Varying Solvent Content in Added Solvent as between Solvent Addition During
the
Start-up Phase and Solvent Addition During Various Stages of the SAGD
Production Phase
[0061] In
some embodiments, for example, a process for producing bitumen from an oil
sands reservoir through a production well 106 that is disposed in fluid
communication with an
injection well 104 via an interwell region 108. The process includes
establishing fluid
communication, through the interwell region 108, between the injection well
104 and the
production well 106. The establishing fluid communication includes injecting a
start-up phase
fluid 118 into the injection well 104 for conducting of the injected start-up
phase fluid to the oil
sands reservoir such that thermal communication between the start-up phase
fluid and the
bitumen within the interwell region is effected. The effected thermal
communication is such that
the bitumen within the interwell region is mobilized. The mobilized bitumen
drains to the
production well 106, resulting in the creation of a fluid passage, for
enabling the locally
entrained reservoir hydrocarbons, including bitumen, to escape the interwell
region 108. As
more bitumen is mobilized and drains to the production well 106, the fluid
passage grows and
eventually effects fluid communication between the injection well 104 and the
production well
106. The start-up phase fluid includes steam and a start-up phase solvent, the
start-up phase
solvent consisting of one or more start-up phase solvent hydrocarbons. After
the fluid
communication has been established, a SAGD production phase is operated. The
process further
includes, during a first stage of the SAGD production phase, injecting a first
production
initiating fluid into the injection well 104 for conducting of the injected
production initiating
fluid to the oil sands reservoir for effecting mobilization of bitumen within
the oil sands reservoir
such that a first mobilized bitumen is conducted through the interwell region
108 to the
production well 106. The first production initiating fluid includes steam and
a production phase
solvent, the production phase solvent consisting of one or more production
phase solvent
hydrocarbons. The first mobilized bitumen is recovered through the production
well 106.
Subsequently, the injecting of the first production initiating fluid is
suspended, such that the first
stage of the SAGD production phase is completed. The ratio of moles of start-
up phase solvent to
steam within the start-up phase fluid is greater (such as, for example, 10%
greater, such as, for
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example, 25% greater, such as, for example, 50% greater) than the ratio of
moles of production
phase solvent to steam within the first production initiating fluid.
[0062] In
some embodiments, for example, after completion of the first stage of the SAGD
production phase, a second stage of the SAGD production phase is effected.
During the second
stage of the SAGD production phase, a second production initiating fluid is
injected into the
injection well 104 for conducting of the injected production initiating fluid
to the oil sands
reservoir for effecting mobilization of bitumen within the oil sands reservoir
such that a second
mobilized bitumen is conducted through the interwell region 108 to the
production well 106.
The second production initiating fluid includes steam and a production phase
solvent, the
production phase solvent consisting of one or more production phase solvent
hydrocarbons. The
second mobilized bitumen is recovered through the production well 106.
Subsequently, the
injecting of the second production initiating fluid is suspended, such that
the second stage of the
SAGD production phase is completed. The ratio of moles of production phase
solvent to steam
is greater (such as, for example, 10% greater, such as, for example, 25%
greater, such as, for
example, 50% greater) within the first production initiating fluid relative to
that within the
second production initiating fluid.
[0063] In
those embodiments where the SAGD production phase includes two stages, for
example, the first stage of the SAGD production phase occurs prior to the
steam chamber
reaching the cap rock 300 (see Figure 2), and the second stage of the SAGD
production phase
occurs after the steam chamber has reached the cap rock 300. In some
embodiments, for
example, the first stage may include at least a portion of a "steam chamber
initialization" phase,
at least a portion of a "plateau phase", or at least portions of both. In some
embodiments, for
example, the second stage may include a "lateral growth only" phase, a
"winding down" phase,
or at least portions of both.
(D)
Varying Solvent Composition as Between Solvent Addition During the Start-up
Phase
and Solvent Addition During the Production Phase
[0064] In
some embodiments, for example, it may be suitable to add heavier solvents
during
the start-up phase of the SAGD operation, and to switch to lighter solvents
following the start-up
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phase (such as during the production phase), once inter-well communication has
been
established.
[0065] The ability to choose the appropriate solvent type allows one to
minimize solvent
losses to the reservoir. Using heavier solvents early in the SAGD operation
may be beneficial
because heavier solvents would be able to fall towards the production well 106
at early stages
when there is very little inter-well communication. At later stages of the
SAGD operation, after
inter-well communication has been established (such as during the production
phase), it may be
beneficial to switch to lighter solvents. Lighter solvents would tend not to
condense as early as
heavier solvents, and would stay in the vapour phase within the steam chamber.
[0066] At later stages of a SAGD operation (e.g. during the production
phase), if the solvent
selected is too heavy, solvent losses may be greater due to retention of
condensed solvent in the
depleted zone. In the start-up phase of a SAGD operation, it should be
possible to use heavier
solvents, as solvent short-circuiting to the production well 106 actually
promotes communication
between the two wells.
100671 In this respect, in some embodiments, for example there is provided
a process for
producing bitumen from an oil sands reservoir through a production well 106
that is disposed in
fluid communication with an injection well 104 via an interwell region 108.
The process
includes establishing fluid communication, through the interwell region 108,
between the
injection well 104 and the production well 106. The establishing fluid
communication includes
injecting a start-up phase fluid 118 into the injection well 104 for
conducting of the injected
start-up phase fluid to the oil sands reservoir such that thermal
communication between the start-
up phase fluid and the bitumen within the interwell region is effected. The
effected thermal
communication is such that the bitumen within the interwell region is
mobilized. The mobilized
bitumen drains to the production well 106, resulting in the creation of a
fluid passage, for
enabling the locally entrained reservoir hydrocarbons, including bitumen, to
escape the interwell
region 108. As more bitumen is mobilized and drains to the production well
106, the fluid
passage grows and eventually effects fluid communication between the injection
well 104 and
the production well 106. The start-up phase fluid includes steam and a start-
up phase solvent,
the start-up phase solvent consisting of one or more start-up phase solvent
hydrocarbons. After
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the fluid communication has been established, a production-initiating fluid
116 is injected into
the injection well 104 for conducting of the injected production-initiating
fluid to the oil sands
reservoir for effecting mobilization of bitumen within the oil sands reservoir
such that mobilized
bitumen is conducted through the interwell region 108 to the production well
106. The
production-initiating fluid includes steam and a production phase solvent, the
production phase
solvent consisting of one or more production phase solvent hydrocarbons. The
mobilized
bitumen is recovered through the production well 106. The density of the start-
up phase solvent
within the start-up phase fluid is greater than the density of the production
phase solvent within
the production-initiating fluid. In some embodiments, for example, the density
of the start-up
phase solvent within the start-up phase fluid is at least 10% greater than the
density of the
production phase solvent within the production-initiating fluid. In some
embodiments, for
example, the density of the start-up phase solvent within the start-up phase
fluid is at least 20%
greater than the density of the production phase solvent within the production-
initiating fluid. In
some embodiments, for example, the density of the start-up phase solvent
within the start-up
phase fluid is at least 30% greater than the density of the production phase
solvent within the
production-initiating fluid. In some embodiments, for example, at least 70 mol
% (such as, for
example, at least 80 mol %, such as, for example, at least 90 mol %) of the
start-up phase
solvent, of the start-up phase fluid, consists of heavy hydrocarbon material,
based on the total
number of moles of the start-up phase solvent being injected, and less than 35
mol % (such as,
for example, less than 25 mol %, such as, for example, less than 15 mol %) of
the production
phase solvent, of the production-initiating fluid, consists of light
hydrocarbon material, based on
the total number moles of the production phase solvent being injected, wherein
the production
phase solvent has a lower molar concentration of heavy hydrocarbon material
than the start-up
phase solvent. In some embodiments, for example, the vapour pressure of the
production-
initiating fluid is greater than the vapour pressure of the start-up phase
fluid. In some of these
embodiments, for example, the vapour pressure of the production-initiating
fluid is greater than
the vapour pressure of the start-up phase fluid by at least 10%, such as, for
example, at least
20%, such as, for example, at least 30%.
[0068] In another respect, there is provided another process for producing
bitumen from an
oil sands reservoir through a production well 106 that is disposed in fluid
communication with an
injection well 104 via an interwell region 108. The process includes
establishing fluid
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communication, through the interwell region 108, between the injection well
104 and the
production well 106. The establishing fluid communication includes injecting a
start-up phase
fluid 118 into the injection well 104 for conducting of the injected start-up
phase fluid to the oil
sands reservoir such that thermal communication between the start-up phase
fluid and the
bitumen within the interwell region is effected. The effected thermal
communication is such that
the bitumen within the interwell region is mobilized. The mobilized bitumen
drains to the
production well 106, resulting in the creation of a fluid passage, for
enabling the locally
entrained reservoir hydrocarbons, including bitumen, to escape the interwell
region 108. As
more bitumen is mobilized and drains to the production well 106, the fluid
passage grows and
eventually effects fluid communication between the injection well 104 and the
production well
106. The start-up phase fluid includes steam and a start-up phase solvent, the
start-up phase
solvent consisting of one or more start-up phase solvent hydrocarbons. After
the fluid
communication has been established, a production-initiating fluid is injected
into the injection
well 104 for conducting of the injected production-initiating fluid to the oil
sands reservoir for
effecting mobilization of bitumen within the oil sands reservoir such that
mobilized bitumen is
conducted through the interwell region 108 to the production well 106. The
production-initiating
fluid includes steam and a production phase solvent, the production phase
solvent consisting of
one or more production phase solvent hydrocarbons. The mobilized bitumen is
recovered
through the production well 106. The weight average molecular weight of the
start-up phase
solvent within the start-up phase fluid is greater than the weight average
molecular of the
production phase solvent within the production-initiating fluid. In some
embodiments, for
example, the weight average molecular weight of the start-up phase solvent
within the start-up
phase fluid is at least 10% greater than the weight average molecular weight
of the production
phase solvent within the production-initiating fluid. In some embodiments, for
example, the
weight average molecular weight of the start-up phase solvent within the start-
up phase fluid is at
least 20% greater than the weight average molecular weight of the production
phase solvent
within the production-initiating fluid. In some embodiments, for example, the
weight average
molecular weight of the start-up phase solvent within the start-up phase fluid
is at least 30%
greater than the weight average molecular weight of the production phase
solvent within the
production-initiating fluid. In some embodiments, for example, at least 70 mol
% (such as, for
example, at least 80 mol %, such as, for example, at least 90 mol %) of the
start-up phase
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solvent, of the start-up phase fluid, consists of heavy hydrocarbon material,
based on the total
number of moles of the start-up phase solvent being injected, and less than 35
mol % (such as,
for example, less than 25 mol %, such as, for example, less than 15 mol %) of
the production
phase solvent, of the production-initiating fluid, consists of light
hydrocarbon material, based on
the total number moles of the production phase solvent being injected, wherein
the production
phase solvent has a lower molar concentration of heavy hydrocarbon material
than the start-up
phase solvent. In some embodiments, for example, the vapour pressure of the
production-
initiating fluid is greater than the vapour pressure of the start-up phase
fluid. In some of these
embodiments, for example, the vapour pressure of the production-initiating
fluid is greater than
the vapour pressure of the start-up phase fluid by at least 10%, such as, for
example, at least
20%, such as, for example, at least 30%.
[0069] In another respect, there is provided another process for producing
bitumen from an
oil sands reservoir through a production well 106 that is disposed in fluid
communication with an
injection well 104 via an interwell region 108. The process includes
establishing fluid
communication, through the interwell region 108, between the injection well
104 and the
production well 106. The establishing fluid communication includes injecting a
start-up phase
fluid 118 into the injection well 104 for conducting of the injected start-up
phase fluid to the oil
sands reservoir such that thermal communication between the start-up phase
fluid and the
bitumen within the interwell region is effected. The effected thermal
communication is such that
the bitumen within the interwell region is mobilized. The mobilized bitumen
drains to the
production well 106, resulting in the creation of a fluid passage, for
enabling the locally
entrained reservoir hydrocarbons, including bitumen, to escape the interwell
region 108. As
more bitumen is mobilized and drains to the production well 106, the fluid
passage grows and
eventually effects fluid communication between the injection well 104 and the
production well
106. The start-up phase fluid includes steam and a start-up phase solvent. The
start-up phase
solvent consisting of one or more start-up phase solvent hydrocarbons. After
the fluid
communication has been established, a production-initiating fluid is injected
into the injection
well 104 for conducting of the injected production-initiating fluid to the oil
sands reservoir for
effecting mobilization of bitumen within the oil sands reservoir such that
mobilized bitumen is
conducted through the interwell region 108 to the production well 106. The
production-initiating
fluid includes steam and a production phase solvent. The production phase
solvent consists of
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one or more production phase solvent hydrocarbons. The mobilized bitumen is
recovered
through the production well 106. At least 70 mol % (such as, for example, at
least 80 mol %,
such as, for example, at least 90 mol %) of the start-up phase solvent, of the
start-up phase fluid,
consists of heavy hydrocarbon material, based on the total number of moles of
the start-up phase
solvent being injected, and less than 35 mol % (such as, for example, less
than 25 mol %, such
as, for example, less than 15 mol %) of the production phase solvent, of the
production-initiating
fluid, consists of light hydrocarbon material, based on the total number of
moles of the
production phase solvent being injected, wherein the production phase solvent
has a lower molar
concentration of heavy hydrocarbon material than the start-up phase solvent.
In some
embodiments, for example, the vapour pressure of the production-initiating
fluid is greater than
the vapour pressure of the start-up phase fluid. In some of these embodiments,
for example, the
vapour pressure of the production-initiating fluid is greater than the vapour
pressure of the start-
up phase fluid by at least 10%, such as, for example, at least 20%, such as,
for example, at least
30%.
(D)
Multicomponent solvents for use within the start-up phase solvent or the
production
phase solvent
[0070] As
mentioned above, either one, or both of, the start-up phase solvent and the
production phase solvent may be a single or multi-component solvent. Multi-
component
solvents allow for operational flexibility, as the functionality of the
solvent may be preserved
over a wider range of operating conditions.
[0071]
Additionally, in producing a solvent, by combining two or more hydrocarbon
compounds, advantageously, the characteristics of the resulting produced
solvent may be more
favourable to effecting mobilization of bitumen, relative to each one of the
constituent
hydrocarbons, in isolation. In some embodiments, for example, at least one of
vapour pressure,
solubility, and viscosity of the produced solvent may be sufficiently
different from that of each
one of the constituent hydrocarbons, in isolation, such that the resulting
produced solvent may be
more favourable to effecting mobilization of bitumen, relative to each one of
the constituent
hydrocarbons, in isolation.
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100721 In this respect, the solvent includes heavy hydrocarbon material and
light
hydrocarbon. A suitable solvent composition is illustrated in Figure 3.
100731 In some embodiments, for example, the solvent includes at least 50
mole % of heavy
hydrocarbon material having a total number of carbon atoms of seven (7) or
more, based on the
total number of moles of the solvent. In some of these embodiments, for
example, the solvent
includes at least 60 mole % of heavy hydrocarbon material having a total
number of carbon
atoms of seven (7) or more, based on the total number of moles of the solvent.
In some of these
embodiments, for example, the solvent includes at least 70 mole % of heavy
hydrocarbon
material having a total number of carbon atoms of seven (7) or more, based on
the total number
of moles of the solvent.
[0074] Heavy hydrocarbons are favourable to bitumen mobilization, in some
respects, as
heavy hydrocarbons are more soluble within bitumen relative to light
hydrocarbons. The
dissolving of the heavy hydrocarbon within the bitumen produces a fluid having
a reduced
viscosity, relative to that of bitumen, in isolation, thereby improving the
mobility of bitumen
within the reservoir. However, generally speaking, heavy hydrocarbons,
relative to light
hydrocarbons, are more viscous. Accordingly, the effective viscosity
reduction, effected by the
dissolution of a heavy hydrocarbon within the bitumen, may not be sufficiently
significant to
effect a sufficiently appreciable increase in the mobility of bitumen within
the reservoir. As
well, generally speaking, heavy hydrocarbons, relative to light hydrocarbons,
have lower vapour
pressures and will, therefore, condense at higher temperatures, which means
that the use of
heavy hydrocarbons as a solvent is more sensitive to temperature decreases.
[0075] Combining the heavy hydrocarbon material with the light hydrocarbon
material
produces a solvent having a lower viscosity relative to the heavy hydrocarbon
material, in
isolation, and also having a higher vapour pressure relative to the heavy
hydrocarbon material, in
isolation. In this respect, such combination mitigates at least some of the
characteristics of the
heavy hydrocarbon material that are detrimental to bitumen production, while
still benefiting
from the favourable solubility characteristics of the heavy hydrocarbon
material within bitumen.
[0076] In some embodiments, for example, the start-up phase fluid includes
0.1 to 30 mole
A of heavy hydrocarbon material of the start-up phase solvent within the start-
up phase fluid,
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based on the total number of moles of the start-up phase fluid. In some of
these embodiments,
for example, the start-up phase fluid includes 15 to 25 mole % of heavy
hydrocarbon material of
the start-up phase solvent within the start-up phase fluid, based on the total
number of moles of
the start-up phase fluid.
[0077] In
some embodiments, for example, the production-initiating fluid includes 0.1 to
30
mole % of heavy hydrocarbon material of the production phase solvent within
the production-
initiating fluid, based on the total number of moles of the production-
initiating fluid. In some
embodiments, for example, the production-initiating fluid includes 15 to 25
mole % of heavy
hydrocarbon material of the production phase solvent within the production-
initiating fluid,
based on the total number of moles of the production-initiating fluid.
(E)
Selecting composition of the start-up phase fluid or the production-initiating
fluid such
that the admixed solvent is in a vapour state when supplied to the reservoir
[0078] In
some embodiments, for example, the composition of the start-up phase fluid is
selected such that the start-up phase solvent is disposed, or substantially
disposed, in a vapour
state when supplied to the oil sands reservoir. After the supplying, the start-
up phase fluid
becomes disposed in thermal communication with bitumen within the interwell
region 108, and
transfers heat to the bitumen such that condensation of at least a fraction of
the start-up phase
solvent is effected to produce condensed start-up phase solvent. After the
condensing, the
condensed start-up phase solvent mixes with the bitumen within the oil sands
reservoir such that
dissolution of the produced condensed start-up phase solvent into the bitumen
is effected to
produce a bitumen-comprising mixture. The bitumen-comprising mixture is then
drained, by
gravity, to the production well 106, thereby contributing to the establishment
of interwell
communication (such as in the form of a steam chamber) between the injection
well 104 and the
production well 106.
[0079] The
selection is based upon information embodied in a multicomponent phase
diagram for the components of the start-up phase fluid. In some embodiments,
for example, the
selected composition of the start-up phase fluid is disposed within the vapour
region of the
multicomponent phase diagram at the temperature and pressure of the interwell
region 108 of the
oil sands reservoir to which the start-up phase fluid is being supplied, by
either one, or both of,
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the injection well 104 and the production well 106, during the start-up phase
of SAGD. It is
understood that information embodied in a multicomponent phase diagram is not
limited by the
manner such information is presented, such as by a graphical illustration, and
extends, for
example, to any electronic or digital form of such presentation.
[0080] In some embodiments, for example, the start-up phase solvent of the
start-up phase
fluid is a single component solvent (i.e. one hydrocarbon) or a multicomponent
solvent (i.e. two
or more hydrocarbons).
[0081] In some embodiments, for example, the composition of the production-
initiating fluid
is selected such that the production phase solvent is disposed in a vapour
state when supplied to
the oil sands reservoir. After the supplying, the production-initiating fluid
becomes disposed in
thermal communication with bitumen within the oil sands region, and transfers
heat to the
bitumen such that condensation of at least a fraction of the production phase
solvent is effected
to produce condensed production phase solvent. After the condensing, the
condensed production
phase solvent mixes with the bitumen within the oil sands reservoir such that
dissolution of the
bitumen by the produced condensed production phase solvent is effected to
produce a bitumen-
comprising mixture. The bitumen-comprising mixture is then drained, by
gravity, to the
production well, and is then produced via the production well.
[0082] In some embodiments, for example, the selection is based upon a
multicomponent
phase diagram for the components of the production-initiating fluid. In some
embodiments, for
example, the selected composition of the production-initiating fluid is
disposed within the vapour
region of the multicomponent phase diagram at the temperature and pressure of
the oil sands
reservoir to which the production-initiating fluid is being supplied by the
injection well during
the production phase of SAGD. It is understood that information embodied in a
multicomponent
phase diagram is not limited by the manner such information is presented, such
as by a graphical
illustration, and extends, for example, to any electronic or digital form of
such presentation.
[0083] In some embodiments, for example, the production phase solvent of
the production-
initiating fluid is a single-component solvent or a multicomponent solvent.
(F) Blowdown after completion of SAGD
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[0084] In some embodiments, for example, upon the completion of the
production phase of
SAGD, where, during SAGD, solvent has been co-injected with steam,
sufficiently significant
amounts of residual solvent may remain within the oil sands reservoir, and it
may be desirable to
recover such residual solvent, such as, for example, for purposes of recycle
and re-use.
[0085] In this respect, in some embodiments, for example, a process is
provided for
producing bitumen from an oil sands reservoir through a production well that
is disposed in fluid
communication with an injection well via an interwell region. The process
includes establishing
fluid communication, through the interwell region, between the injection well
and the production
well. The establishing fluid communication includes supplying a start-up phase
fluid via the
injection well or the production well such that thermal communication between
the start-up
phase fluid and the bitumen within the interwell region is effected. The start-
up phase fluid
includes steam. After the fluid communication has been established, during a
SAGD production
phase, a production-initiating fluid is supplied to the oil sands reservoir
via the injection well
such that mobilization of bitumen within the oil sands reservoir is effected,
and such that the
mobilized bitumen is conducted to the production well and produced via the
production well.
The production-initiating fluid includes steam
[0086] At least one of the start-up phase fluid and the production-
initiating fluid also
includes solvent that includes hydrocarbon material. In some embodiments, for
example, both of
the start-up phase fluid and the production-initiating fluid includes solvent
that includes
hydrocarbon material. In some embodiments, for example, where the start-up
phase fluid
includes steam and solvent that includes hydrocarbon material, the start-up
phase fluid may
include between 0.1 and 30 mol % (such as, for example, between 3 and 30 mol
%) of the start-
up phase solvent, based on the total number of moles of the start-up phase
fluid. In some
embodiments, for example, where the production-initiating fluid includes steam
and solvent that
includes hydrocarbon material, the production-initiating fluid may include
between 0.1 and 30
mol % (such as, for example, between 3 and 30 mol %) of production phase
solvent, based on
the total moles of the production-initiating fluid.
[0087] Completion of the SAGD production phase is defined by the suspension
of the
supplying of the production-initiating fluid to the oil sands reservoir via
the injection well. Prior
31
to the suspension of the production-initiating fluid to the oil sands
reservoir via the injection
well, and while the production-initiating fluid is being supplied to the oil
sands reservoir via the
injection well, the reservoir is disposed at a pre-SAGD production phase
suspension pressure.
After the supplying of the production-initiating fluid to the oil sands
reservoir via the injection
well has been suspended, and after the pressure within the oil sands reservoir
has been reduced
from a pre-SAGD production phase suspension pressure, and while the oil sands
reservoir is
being vented via at least one of the injection well and the production well,
collecting gaseous
material that is being conducted via the at least one of the injection well
and the production well
such as at least some of the supplied solvent is recovered. In some
embodiments, for example,
the pressure reduction is at least a 25% pressure reduction. In some
embodiments, for example,
the pressure reduction is at least a 50% pressure reduction. In some
embodiments, for example,
the pressure reduction is such that the oil sands reservoir is disposed at
reservoir pressure.
[0088]
In the above description, for purposes of explanation, numerous details are
set forth in
order to provide a thorough understanding of the present disclosure. However,
it will be
apparent to one skilled in the art that these specific details are not
required in order to practice
the present disclosure.
Although certain dimensions and materials are described for
implementing the disclosed example embodiments, other suitable dimensions
and/or materials
may be used within the scope of this disclosure. All such modifications and
variations, including
all suitable current and future changes in technology, are believed to be
within the sphere and
scope of the present disclosure.
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Date Recue/Date Received 2021-05-28
