Note: Descriptions are shown in the official language in which they were submitted.
,
,
INTEGRATED APPROACH TO ENHANCE THE PERFORMANCE OF GRAVITY
DRAINAGE PROCESSES
Technical Field
[0001] The present disclosure relates generally to methods of
recovering
hydrocarbons, and more specifically to methods of enhancing gravity drainage
processes
for recovering bitumen and heavy oil from underground reservoirs.
Background
[0002] This section is intended to introduce various aspects of the
art that may be
associated with the present disclosure. This discussion aims to provide a
framework to
facilitate a better understanding of particular aspects of the present
disclosure.
Accordingly, it should be understood that this section should be read in this
light, and not
necessarily as an admission of prior art.
[0003] Hydrocarbon resources continue to be heavily relied on for
fuels and
chemical feedstock. Hydrocarbons are generally recovered from subsurface
formations
known as "reservoirs." Different methods for removing or extracting
hydrocarbons from
reservoirs are used depending on the physical properties of the reservoir,
such as the
permeability of the rock containing the hydrocarbons, the ability of the
hydrocarbons to
flow through the subsurface formations, and the proportion of hydrocarbons
present,
among other things.
[0004] One exemplary method for removing (or extracting)
hydrocarbons from
reservoirs is steam-assisted gravity drainage (SAGD). SAGD is an enhanced oil
recovery technology for producing heavy crude oil and bitumen. It is an
advanced form
of steam stimulation in which a pair of horizontal wells is drilled into the
oil reservoir, one
a few metres above the other. Steam is continuously injected into the upper
wellbore to
heat the oil and reduce its viscosity, causing the heated oil to drain into
the lower wellbore,
where it is pumped out. SAGD and SAGD-based processes have been widely applied
for
hydrocarbon recovery from oil sands reservoirs.
[0005] Gravity drainage processes such as SAGD are usually operated
at lower
pressures when compared to cyclic processes (e.g. cyclic steam stimulation
(CSS), liquid
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, addition to steam for enhancing recovery (LASER) and cyclic solvent process
(CSP)) and
are therefore more sensitive to reservoir heterogeneities, particularly
vertical flow barriers.
[0006] Start-up processes utilizing steam to establish well
communication in SAGD
and SAGD-based operations typically require months, which delays recovery of
bitumen.
Further, small spacing between neighbouring SAGD wells is required to achieve
high
estimated ultimate recovery (EUR) which can lead to high initial capital
expenses
(CAPEX) and communication between neighbouring chambers. Once steam reaches
the
top of top of the reservoir, the steam efficiency will start to drop (i.e.
steam to oil ratio, or
SOR, will rise) due to heat loss to the overburden (non-reservoir rock).
[0007] Further, as shown in Figure 1, unswept regions form between
neighbouring
SAGD well pairs that are hard to target after SAGD extraction is exhausted.
InfiII drilling
between SAGD well pairs has been employed by some operators to target unswept
bitumen, maintain or increase oil rate, and increase the EUR. Most of the
infill methods,
however, involve either drilling a well pair for similar gravity-drainage
operation or drilling
a single well to inject a non-condensable gas (NCG) for a flooding-based
process.
[0008] Accordingly, there is a need for improved methods of enhancing
gravity
drainage for bitumen recovery from oil sands reservoirs.
Summary
[0009] The present disclosure provides methods of recovering bitumen
from a
reservoir. In some embodiments, the methods include operating a first injector-
first
producer well pair under a first gravity drainage process, the first injector-
first producer
well pair forming a first gravity drainage chamber in the subterranean
reservoir; operating
a second injector-second producer well pair under a second gravity drainage
process, the
second injector-second producer well pair forming a second gravity drainage
chamber in
the subterranean reservoir; providing an infill well in an unswept region
formed between
the first gravity drainage chamber and the second gravity drainage chamber;
operating
the infill well under a cyclic process utilizing a mobilizing fluid to form a
mobilized region
of the infill well, the operating including injecting the mobilizing fluid
into the infill well and
producing a mixture of the injected mobilizing fluid and bitumen from the
infill well;
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operating the infill well under a flooding process utilizing a driving fluid
to displace bitumen
in the mobilized region towards the first and second producer wells of the
first injector-
first producer well pair and the second injector-second producer well pair;
and recovering
the bitumen from the first and second producer wells of the first injector-
first producer well
pair and the second injector-second producer well pair.
[0010] The operating the infill well under the cyclic process may begin
during either
an early stage or a mid-stage of the first and second gravity drainage
processes when
the first gravity drainage chamber and the second gravity drainage chamber are
spaced
from each other.
[0011] The operating the infill well under the cyclic process may begin
during a late
stage of the first and second gravity drainage processes when the first
gravity drainage
chamber and the second gravity drainage chamber are in communication with each
other.
[0012] The operating the infill well under the flooding process may begin
during a
late stage of the first and second gravity drainage processes when the first
gravity
drainage chamber and the second gravity drainage chamber are in communication
with
each other.
[0013] The providing the infill well in the unswept region formed between
the first
gravity drainage chamber and the second gravity drainage chamber may include
providing the infill well at a position vertically offset from the first and
second producer
wells of the first injector-first producer well pair and the second injector-
second producer
well pair.
[0014] The providing the infill well at a position vertically offset from
the first and
second producer wells of the first injector-first producer well pair and the
second injector-
second producer well pair may include providing the infill well at a position
vertically offset
from the first and second producer wells in a direction towards overburden of
the
reservoir.
[0015] The mobilizing fluid may include a light hydrocarbon or a
combination of
light hydrocarbons in vapor or liquid form.
[0016] The mobilizing fluid may include steam.
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,
[0017] The mobilizing fluid may include primarily the light hydrocarbon
or the
combination of light hydrocarbons.
[0018] The mobilizing fluid may include primarily the steam.
[0019] The driving fluid may include a light hydrocarbon or a
combination of light
hydrocarbons, primarily in vapor phase.
[0020] The driving fluid may include steam.
[0021] The driving fluid may include primarily the light hydrocarbon or
the
combination of light hydrocarbons.
[0022] The driving fluid may include primarily the steam.
[0023] The light hydrocarbon may be one of a C2-C7 alkane, a C2-C7 n-
alkane,
an n-pentane, an n-heptane, or a gas plant condensate comprising alkanes,
naphthenes,
and aromatics.
[0024] The cyclic process may be one of a liquid addition to steam for
enhancing
recovery (LASER) process, a cyclic steam stimulation (CSS) process, and a
cyclic solvent
process (CSP).
[0025] The one or both of the first gravity drainage process and the
second gravity
drainage process may be a steam-assisted gravity drainage (SAGD) process, a
solvent-
assisted-steam-assisted gravity drainage (SA-SAGD) process, a heated solvent
vapor-
assisted petroleum extraction (H-VAPEX) process, or any combination thereof.
[0026] The one or both of the first gravity drainage process and the
second gravity
drainage process may be a SA-SAGD process and the solvent in the SA-SAGD
process
is one of a light hydrocarbon, a mixture of light hydrocarbons, dimethyl ether
(DME), and
a mixture of light hydrocarbons with DME.
[0027] The solvent in the SA-SAGD process may be a C2-C7 alkane, a C2-C7
n-
alkane, an n-pentane, an n-heptane, or a gas plant condensate comprising
alkanes,
naphthenes, and aromatics.
[0028] The one or both of the first gravity drainage process and the
second gravity
drainage process may be an H-VAPEX process and the solvent may be one of a
light
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hydrocarbon, a mixture of light hydrocarbons, dimethyl ether (DME), and a
mixture of light
hydrocarbons with DME.
[0029] The solvent may be a C2 to C7 alkane.
[0030] The method may further include operating one well or both wells of
the first
injector-first producer well pair under a first cyclic process at a first
pressure below a
fracture pressure of the reservoir prior to the operating of the first
injector-first producer
well pair under the first gravity drainage process.
[0031] The method may further include operating one well or both wells of
the
second injector-second producer well pair under a second cyclic process at a
second
pressure below a fracture pressure of the reservoir prior to the operating of
the second
injector-second producer well pair under the second gravity drainage process.
[0032] The providing the infill well in the unswept region formed between
the first
gravity drainage chamber and the second gravity drainage chamber may include
injecting
the mobilizing fluid into the infill well through flow control devices in the
infill well to control
delivery of the mobilizing fluid to target regions along the infill well.
[0033] In some embodiments, the methods of enhancing a gravity drainage
process of recovering bitumen from a reservoir include providing a first
injector-first
producer well pair in the reservoir; providing a second injector-second
producer well pair
in the reservoir, the second injector-second producer well pair spaced from
the first
injector-first producer well pair; operating one or both wells of the first
injector-first
producer well pair under a first cyclic process utilizing a first mobilizing
fluid at a first
pressure below a fracture pressure of the reservoir; operating one or both
wells of the
second injector-second producer well pair under a second cyclic process
utilizing a
second mobilizing fluid at a second pressure below a fracture pressure of the
reservoir;
operating the first injector-first producer well pair under a first gravity
drainage process,
the first injector-first producer well pair forming a first gravity drainage
chamber in the
subterranean reservoir; operating a second injector-second producer well pair
under a
second gravity drainage process, the second injector-second producer well pair
forming
a second gravity drainage chamber in the subterranean reservoir; and
recovering the
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,
,
bitumen from the first and second producer wells of the first injector-first
producer well
pair and the second injector-second producer well pair.
[0034] The first injector well may be operated under the first
cyclic process and the
second injector well may be operated under the second cyclic process.
[0035] The first producer well may be operated under the first
cyclic process and
the second producer well may be operated under the second cyclic process.
[0036] Both wells of the first injector-first producer well pair
may be operated under
the first cyclic process.
[0037] Both wells of the second injector-second producer well pair
may be
operated under the second cyclic process.
[0038] The first cyclic process may include three or less cycles.
[0039] The second cyclic process may include three or less cycles.
[0040] The foregoing has broadly outlined the features of the
present disclosure so
that the detailed description that follows may be better understood.
Additional features
will also be described herein.
[0041] These and other features and advantages of the present
application will
become apparent from the following detailed description taken together with
the
accompanying drawings. However, it should be understood that the detailed
description
and the specific examples, while indicating preferred embodiments of the
application, are
given by way of illustration only, since various changes and modifications
within the spirit
and scope of the application will become apparent to those skilled in the art
from this
detailed description.
Brief Description of the Drawings
[0042] For a better understanding of the various embodiments
described herein,
and to show more clearly how these various embodiments may be carried into
effect,
reference will be made, by way of example, to the accompanying drawings which
show
at least one example embodiment, and which are now described. The drawings are
not
intended to limit the scope of the teachings described herein.
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,
[0043] FIG. 1A is a schematic axial cross section of two pairs of
horizontal
wellbores in a typical SAGD recovery process showing a pair of gravity
drainage
chambers and an unswept region therebetween during an early stage of the SAGD
recovery;
[0044] FIG. 1B is a schematic axial cross section of two pairs of
horizontal
wellbores in a typical SAGD recovery process showing a pair of gravity
drainage
chambers and an unswept region therebetween during a late stage of the SAGD
recovery;
[0045] FIG. 2 is a longitudinal cross-sectional view of the two pairs of
horizontal
wellbores shown in FIGs. 1A and 1B;
[0046] FIG. 3 is a block diagram showing a method of recovering bitumen
from a
reservoir, according to one embodiment;
[0047] FIG. 4A is a diagram showing a pair of gravity drainage chambers
during
an early to mid-stage of a gravity drainage process and an unswept region
during an early
stage of an infill cyclic process between the pair of gravity drainage
chambers of the
method of recovering bitumen from a reservoir of FIG. 3, according to one
embodiment;
[0048] FIG. 4B is a diagram showing the pair of gravity drainage
chambers during
late stage of a gravity drainage process and an unswept region during a late
stage of the
infill cyclic process between the pair of gravity drainage chambers of the
method of
recovering bitumen from a reservoir of FIG. 3, according to one embodiment;
[0049] FIG. 5 is a diagram showing expansion of the unswept region
during the
continuous flooding stage following the infill cyclic process of the method of
recovering
bitumen from a reservoir of FIG. 3, according to one embodiment;
[0050] FIG. 6 is a diagram showing a cyclic solvent process (CSP) as a
startup of
a gravity-drainage process of the method of recovering bitumen from a
reservoir of FIG.
3, according to one embodiment; and
[0051] FIG. 7 is a plane view of targeted delivery of steam/solvent
based on gravity
drainage chamber conformance.
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=
[0052] The skilled person in the art will understand that the drawings,
further
described below, are for illustration purposes only. The drawings are not
intended to limit
the scope of the applicant's teachings in any way. Also, it will be
appreciated that for
simplicity and clarity of illustration, elements shown in the figures have not
necessarily
been drawn to scale. For example, the dimensions of some of the elements may
be
exaggerated relative to other elements for clarity. Further aspects and
features of the
example embodiments described herein will appear from the following
description taken
together with the accompanying drawings.
Detailed Description
[0053] To promote an understanding of the principles of the disclosure,
reference
will now be made to the features illustrated in the drawings and no limitation
of the scope
of the disclosure is hereby intended. Any alterations and further
modifications, and any
further applications of the principles of the disclosure as described herein
are
contemplated as would normally occur to one skilled in the art to which the
disclosure
relates. For the sake of clarity, some features not relevant to the present
disclosure may
not be shown in the drawings.
[0054] At the outset, for ease of reference, certain terms used in this
application
and their meanings as used in this context are set forth. To the extent a term
used herein
is not defined below, it should be given the broadest definition persons in
the pertinent art
have given that term as reflected in at least one printed publication or
issued patent.
Further, the present techniques are not limited by the usage of the terms
shown below,
as all equivalents, synonyms, new developments, and terms or techniques that
serve the
same or a similar purpose are considered to be within the scope of the present
claims.
[0055] As one of ordinary skill would appreciate, different persons may
refer to the
same feature or component by different names. This document does not intend to
distinguish between components or features that differ in name only. In the
following
description and in the claims, the terms "including" and "comprising" are used
in an open-
ended fashion, and thus, should be interpreted to mean "including, but not
limited to."
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,
,
[0056] A "hydrocarbon" is an organic compound that primarily
includes the
elements of hydrogen and carbon, although nitrogen, sulfur, oxygen, metals, or
any
number of other elements may be present in small amounts. Hydrocarbons
generally
refer to components found in heavy oil or in oil sands. Hydrocarbon compounds
may be
aliphatic or aromatic, and may be straight chained, branched, or partially or
fully cyclic.
[0057] A "light hydrocarbon" is a hydrocarbon having carbon numbers
in a range
from 1 to 9.
[0058] "Bitumen" is a naturally occurring heavy oil material.
Generally, it is the
hydrocarbon component found in oil sands. Bitumen can vary in composition
depending
upon the degree of loss of more volatile components. It can vary from a very
viscous,
tar-like, semi-solid material to solid forms. The hydrocarbon types found in
bitumen can
include aliphatics, aromatics, resins, and asphaltenes. A typical bitumen
might be
composed of:
- 19 weight (wt.) percent (%) aliphatics (which can range from 5 wt. % to
30 wt. %
or higher);
- 19 wt. % asphaltenes (which can range from 5 wt. % to 30 wt. % or
higher);
- 30 wt. % aromatics (which can range from 15 wt. % to 50 wt. % or higher);
- 32 wt. % resins (which can range from 15 wt. % to 50 wt. A or higher);
and
- some amount of sulfur (which can range in excess of 7 wt. %), based on
the total
bitumen weight.
[0059] In addition, bitumen can contain some water and nitrogen
compounds
ranging from less than 0.4 wt. % to in excess of 0.7 wt. %. The percentage of
the
hydrocarbon found in bitumen can vary. The term "heavy oil" includes bitumen
as well as
lighter materials that may be found in a sand or carbonate reservoir.
[0060] "Heavy oil" includes oils which are classified by the
American Petroleum
Institute ("API"), as heavy oils, extra heavy oils, or bitumens. The term
"heavy oil" includes
bitumen. Heavy oil may have a viscosity of about 1,000 centipoise (cP) or
more, 10,000
cP or more, 100,000 cP or more, or 1,000,000 cP or more. In general, a heavy
oil has an
API gravity between 22.3 API (density of 920 kilograms per meter cubed
(kg/m3) or 0.920
grams per centimeter cubed (g/cm3)) and 10.00 API (density of 1,000 kg/m3 or 1
g/cm3).
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An extra heavy oil, in general, has an API gravity of less than 10.00 API
(density greater
than 1,000 kg/m3 or 1 g/cm3). For example, a source of heavy oil includes oil
sand or
bituminous sand, which is a combination of clay, sand, water and bitumen.
[0061] The term "viscous oil" as used herein means a hydrocarbon, or
mixture of
hydrocarbons, that occurs naturally and that has a viscosity of at least 10 cP
at initial
reservoir conditions. Viscous oil includes oils generally defined as "heavy
oil" or
"bitumen." Bitumen is classified as an extra heavy oil, with an API gravity of
about 100 or
less, referring to its gravity as measured in degrees on the API Scale. Heavy
oil has an
API gravity in the range of about 22.3 to about 10 . The terms viscous oil,
heavy oil, and
bitumen are used interchangeably herein since they may be extracted using
similar
processes.
[0062] In-situ is a Latin phrase for "in the place" and, in the context
of hydrocarbon
recovery, refers generally to a subsurface hydrocarbon-bearing reservoir. For
example,
in-situ temperature means the temperature within the reservoir. In another
usage, an in-
situ oil recovery technique is one that recovers oil from a reservoir within
the earth.
[0063] The term "subterranean formation" refers to the material existing
below the
Earth's surface. The subterranean formation may comprise a range of
components, e.g.
minerals such as quartz, siliceous materials such as sand and clays, as well
as the oil
and/or gas that is extracted. The subterranean formation may be a subterranean
body of
rock that is distinct and continuous. The terms "reservoir" and "formation"
may be used
interchangeably.
[0064] The term "wellbore" as used herein means a hole in the subsurface
made
by drilling or inserting a conduit into the subsurface. A wellbore may have a
substantially
circular cross section or any other cross-sectional shape. The term "well,"
when referring
to an opening in the formation, may be used interchangeably with the term
"wellbore."
[0065] The term "gravity drainage process" refers to an oil recovery
technique in
which gravity acts as the main driving force for the displacement of oil into
the wellbore
and the voidage volume of oil in the reservoir is replaced by a gas. Gravity
drainage
processes for heavy oil recovery may include a steam-assisted gravity drainage
(SAGD)
process, a solvent-assisted-steam-assisted gravity drainage (SA-SAGD) process,
a
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,
heated solvent vapor-assisted petroleum extraction (H-VAPEX) process, or any
combination thereof.
[0066] The term "cyclic process" refers to an oil recovery
technique in which the
injection of a viscosity reducing agent into a wellbore to stimulate
displacement of the oil
alternates with oil production from the same wellbore and the injection-
production process
is repeated at least once. Cyclic processes for heavy oil recovery may include
a cyclic
steam stimulation (CSS) process, a liquid addition to steam for enhancing
recovery
(LASER) process, a cyclic solvent process (CSP), or any combination thereof.
[0067] The articles "the," "a" and "an" are not necessarily limited
to mean only one,
but rather are inclusive and open ended to include, optionally, multiple such
elements.
[0068] As used herein, the terms "approximately," "about,"
"substantially," and
similar terms are intended to have a broad meaning in harmony with the common
and
accepted usage by those of ordinary skill in the art to which the subject
matter of this
disclosure pertains. It should be understood by those of skill in the art who
review this
disclosure that these terms are intended to allow a description of certain
features
described and claimed without restricting the scope of these features to the
precise
numeral ranges provided. Accordingly, these terms should be interpreted as
indicating
that insubstantial or inconsequential modifications or alterations of the
subject matter
described and are considered to be within the scope of the disclosure.
[0069] "At least one," in reference to a list of one or more
entities should be
understood to mean at least one entity selected from any one or more of the
entity in the
list of entities, but not necessarily including at least one of each and every
entity
specifically listed within the list of entities and not excluding any
combinations of entities
in the list of entities. This definition also allows that entities may
optionally be present
other than the entities specifically identified within the list of entities to
which the phrase
"at least one" refers, whether related or unrelated to those entities
specifically identified.
Thus, as a non-limiting example, "at least one of A and B" (or, equivalently,
"at least one
of A or B," or, equivalently "at least one of A and/or B") may refer, to at
least one, optionally
including more than one, A, with no B present (and optionally including
entities other than
B); to at least one, optionally including more than one, B, with no A present
(and optionally
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including entities other than A); to at least one, optionally including more
than one, A, and
at least one, optionally including more than one, B (and optionally including
other entities).
In other words, the phrases "at least one," "one or more," and "and/or" are
open-ended
expressions that are both conjunctive and disjunctive in operation. For
example, each of
the expressions "at least one of A, B and C," "at least one of A, B, or C,"
"one or more of
A, B, and C," "one or more of A, B, or C" and "A, B, and/or C" may mean A
alone, B alone,
C alone, A and B together, A and C together, B and C together, A, B and C
together, and
optionally any of the above in combination with at least one other entity.
[0070] Where two or more ranges are used, such as but not limited to 1 to
5 or 2
to 4, any number between or inclusive of these ranges is implied.
[0071] As used herein, the phrases "for example," "as an example," and/or
simply
the terms "example" or "exemplary," when used with reference to one or more
components, features, details, structures, methods and/or figures according to
the
present disclosure, are intended to convey that the described component,
feature, detail,
structure, method and/or figure is an illustrative, non-exclusive example of
components,
features, details, structures, methods and/or figures according to the present
disclosure.
Thus, the described component, feature, detail, structure, method and/or
figure is not
intended to be limiting, required, or exclusive/exhaustive; and other
components,
features, details, structures, methods and/or figures, including structurally
and/or
functionally similar and/or equivalent components, features, details,
structures, methods
and/or figures, are also within the scope of the present disclosure. Any
embodiment or
aspect described herein as "exemplary" is not to be construed as preferred or
advantageous over other embodiments.
[0072] In spite of the technologies that have been developed, there
remains a need
in the field for methods of recovering bitumen from a reservoir.
[0073] An integrated approach to mitigate some of above-mentioned
challenges in
the gravity-drainage process targeting startup enhancement, accelerating
production,
increasing EUR, as well as reduction of energy intensity is provided herein.
The proposed
approach involves utilizing and integrating different solvent-assisted or
solvent-dominated
processes and recovery mechanisms (such as a CSP, a LASER process, a solvent
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assisted (SA)-steam flood or solvent flood process, or a combination thereof)
at different
stages of a base gravity-drainage process, which could be steam assisted
gravity
drainage (SAGD), solvent-assisted-steam assisted gravity drainage (SA-SAGD),
heated
vapor extraction (H-VAPEX) or a combination thereof.
[0074] Referring now to Figures 1A and 1B, illustrated therein are
schematic axial
cross-sections of typical SAGD recovery processes. Two pairs of horizontal
wellbores
100, 110 are provided in a formation or reservoir 10 and are spaced apart
vertically by a
distance d. Steam is generally pumped down from the surface through the
overburden 1
and along the upper wellbores 100a, 110a, where it passes into the formation
10 via one
of a number of apertures provided in the wellbore casing. Upper wellbores
100a, 110a
may also be referred to as an injector wellbore or, simply an injector. As
steam is injected,
thermal energy from the steam is transferred to the formation. This thermal
energy
increases the temperature of petroleum products present in the formation 10
(e.g. heavy
crude oil or bitumen), which reduces their viscosity and allows them to flow
downwards
under the influence of gravity towards the lower wellbores 100b, 110b,
respectively,
where it passes into the wellbores 100b, 110b via one of a number of apertures
provided
in the wellbore casing. Lower wellbores 100b, 110b may also be referred to as
producer
wellbores or, simply as a producer.
[0075] As shown in Figure 1A, as the steam enters the reservoir, gravity
drainage
chambers 20a and 20b are formed and an unswept region 30 forms therebetween.
While
during normal operation lower wellbores 100b, 110b act as producers (i.e.
fluid is
extracted from the formation via the wellbores 100b, 110b), it will be
appreciated that
wellbores 100b, 110b may alternatively act as an injector. For example, during
start-up of
a SAGD process, steam may be pumped into both wellbores of each pair of
wellbores to
initially heat the formation proximate both the upper 100a, 110a and lower
100b, 110b
wellbores, respectively, following which wellbores 100b, 110b may be
transitioned to
producers by discontinuing the steam flow in these wellbores.
[0076] Turning to Figure 1B, as the SAGD process continues and steam is
pumped
through the upper wellbores 100a, 110a, petroleum products present in the
formation 10
flow downwards under the influence of gravity towards the lower wellbores
100b, 110b
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and the gravity drainage chambers 20a and 20b grow. Eventually, at a late
phase of the
SAGD process, the gravity drainage chambers 20a and 20b merge and form a
common
gravity drainage chamber. At this point, removal of additional petroleum
products present
in the formation 10 using the SAGD process becomes inefficient.
[0077]
Figure 2 illustrates a schematic longitudinal cross-section of the typical
SAGD recovery process shown in Figure 1. As described above, steam is pumped
down
from the surface through the heels 104, 114 of the injector wellbores 100, 110
and along
the horizontal segments 106, 116 towards the toes 108, 118. A number of
oufflow
locations (e.g. screens, perforations, or other apertures) are provided along
the injector
wellbore casings to allow the steam to access the formation. Heated petroleum
products
and condensate from the injected fluids flow down through the formation 10 and
into
producer wellbores 100b, 110b through one of a number of inflow locations
(e.g. screens,
perforations, or other apertures) provided along the horizontal segments 106,
116 of the
producer wellbore casings between the heels 104, 114 of the producer wellbores
and the
toes 108, 118, respectively. One or more artificial lift devices (not shown)
(e.g.
electrical submersible pumps) is used to pump fluids collected along the
horizontal
segments of the producer wellbores 100b, 110b up to the surface.
[0078]
Referring now to Figure 3, illustrated therein is a method 300 of recovering
bitumen from a reservoir. Method 300 builds upon the typical SAGD process
described
in Figures 1 and 2 and includes providing an infill well between the two pairs
of injector-
producer wells to extract petroleum products form the unswept region
therebetween.
[0079]
At a step 302 of the method 300, a first injector-first producer well pair is
operated under a first gravity drainage process. At a step 304 of the method
300, a second
injector-second producer well pair is operated under a second gravity drainage
process.
It should be noted that steps 302 and 304 may occur concurrently in the method
300.
[0080]
Optionally, prior to the steps 302 and 304 of operating the first injector-
first
producer well pair and the second injector-second producer well pair under a
gravity
drainage process, one or both of the first injector-first producer well pair
and the second
injector-second producer well pair may be operated in a cyclic mode. In some
embodiments, operating one or both of the first injector-first producer well
pair and the
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CA 3027074 2018-12-11
,
,
second injector-second producer well pair in a cyclic mode may enhance startup
(e.g.
reduce time to producing of oil from the producer wells).
[0081] As shown in Figure 4, in one example, a first injector-first
producer well pair
400 is spaced apart from a second injector-first producer well pair 410.
Operation of the
first injector-first producer well pair 400 under a first gravity drainage
process forms a first
gravity drainage chamber 420a in the formation or reservoir 403 and operation
of the
second injector-second producer well pair 410 under a second gravity drainage
process
forms a second gravity drainage chamber 420b in the formation or reservoir
403.
[0082] The first gravity-drainage process and the second gravity-
drainage process
may be the same gravity-drainage process or may be differing gravity-drainage
processes. In some embodiments, one or both of the first gravity drainage
process and
the second gravity drainage process is a SAGD process, a solvent-assisted-
steam-
assisted gravity drainage (SA-SAGD) process, a heated solvent vapor-assisted
petroleum extraction (H-VAPEX) process, or any combination thereof.
[0083] In the aforementioned gravity drainage processes, solvents
may be used to
enhance the extraction of petroleum products from the reservoir 403. For
instance,
solvents are used in SA-SAGD processes to enhance the extraction of petroleum
products from the reservoir 403. In some embodiments where one or both of the
first
gravity drainage process and the second gravity drainage process is a SA-SAGD
process, the solvent used in the SA-SAGD may be a light hydrocarbon, a mixture
of light
hydrocarbons or dimethyl ether. In other embodiments, the solvent may be a C2-
C7
alkane, a C2-C7 n-alkane, an n-pentane, an n-heptane, or a gas plant
condensate
comprising alkanes, naphthenes, and aromatics.
[0084] In other embodiments, one or both of the first gravity
drainage process and
the second gravity drainage process may be an H-VAPEX process. In these
embodiments, the solvent used in the H-VAPEX process may also be one of a
light
hydrocarbon, a mixture of light hydrocarbons and dimethyl ether. In one
specific example,
the solvent used in an H-VAPEX process may be a C2 to C7 alkane.
[0085] In other embodiments, the solvent may be a light, but
condensable,
hydrocarbon or mixture of hydrocarbons comprising ethane, propane, butane, or
pentane.
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The solvent may comprise at least one of ethane, propane, butane, pentane, and
carbon
dioxide. The solvent may comprise greater than 50% C2-05 hydrocarbons on a
mass
basis. The solvent may be greater than 50 mass% propane, optionally with
diluent when
it is desirable to adjust the properties of the injectant to improve
performance.
[0086]
Additional injectants may include CO2, natural gas, C5+ hydrocarbons,
ketones, and alcohols. Non-solvent injectants that are co-injected with the
solvent may
include steam, non-condensable gas, or hydrate inhibitors. The solvent
composition may
comprise at least one of diesel, viscous oil, natural gas, bitumen, diluent,
C5+
hydrocarbons, ketones, alcohols, non-condensable gas, water, biodegradable
solid
particles, salt, water soluble solid particles, and solvent soluble solid
particles.
[0087]
To reach a desired injection pressure of the solvent composition, a
viscosifier may be used in conjunction with the solvent. The viscosifier may
be useful in
adjusting solvent viscosity to reach desired injection pressures at available
pump rates.
The viscosifier may include diesel, viscous oil, bitumen, and/or diluent. The
viscosifier
may be in the liquid, gas, or solid phase. The viscosifier may be soluble in
either one of
the components of the injected solvent and water. The viscosifier may
transition to the
liquid phase in the reservoir before or during production. In the liquid
phase, the
viscosifiers are less likely to increase the viscosity of the produced fluids
and/or decrease
the effective permeability of the formation to the produced fluids.
[0088]
The solvent composition may comprise (i) a polar component, the polar
component being a compound comprising a non-terminal carbonyl group; and (ii)
a non-
polar component, the non-polar component being a substantially aliphatic
substantially
non-halogenated alkane. The solvent composition may have a Hansen hydrogen
bonding parameter of 0.3 to 1.7 (or 0.7 to 1.4). The solvent composition may
have a
volume ratio of the polar component to non-polar component of 10:90 to 50:50
(or 10:90
to 24:76, 20:80 to 40:60, 25:75 to 35:65, or 29:71 to 31:69). The polar
component may
be, for instance, a ketone or acetone. The non-polar component may be, for
instance, a
C2-C7 alkane, a C2-C7 n-alkane, an n-pentane, an n-heptane, or a gas plant
condensate
comprising alkanes, naphthenes, and aromatics. For further details and
explanation of
the Hansen Solubility Parameter System see, for example, Hansen, C. M. and
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CA 3027074 2018-12-11
Beerbower, Kirk-Othmer, Encyclopedia of Chemical Technology, (Suppl. Vol. 2nd
Ed),
1971, pp 889-910 and "Hansen Solubility Parameters A User's Handbook" by
Charles
Hansen, CRC Press, 1999.
[0089]
The solvent composition may comprise (i) an ether with 2 to 8 carbon
atoms; and (ii) a non-polar hydrocarbon with 2 to 30 carbon atoms. Ether may
have 2 to
8 carbon atoms. Ether may be di-methyl ether, methyl ethyl ether, di-ethyl
ether, methyl
iso-propyl ether, methyl propyl ether, di-isopropyl ether, di-propyl ether,
methyl iso-butyl
ether, methyl butyl ether, ethyl iso-butyl ether, ethyl butyl ether, iso-
propyl butyl ether,
propyl butyl ether, di-isobutyl ether, or di-butyl ether. Ether may be di-
methyl ether. The
non-polar hydrocarbon may a C2-C30 alkane. The non-polar hydrocarbon may be a
C2-
05 alkane. The non-polar hydrocarbon may be propane. The ether may be di-
methyl
ether and the hydrocarbon may be propane. The volume ratio of ether to non-
polar
hydrocarbon may be 10:90 to 90:10; 20:80 to 70:30; or 22.5:77.5 to 50:50.
[0090]
The solvent composition may comprise at least 5 mol A) of a high-aromatics
component (based upon total moles of the solvent composition) comprising at
least 60
wt. A aromatics (based upon total mass of the high-aromatics component). One
suitable
and inexpensive high-aromatics component is gas oil from a catalytic cracker
of a
hydrocarbon refining process, also known as a light catalytic gas oil (LCGO).
[0091]
At a third step 306, an infill wellbore 440 is provided (e.g. drilled) in an
unswept region 430 formed between the first gravity drainage chamber 420a and
the
second gravity drainage chamber 420b that form during the steps 302 and 304.
[0092]
The infill wellbore 440 is generally a horizontal wellbore similar in
structure
to the wellbores 100a, 100b, 110a and 110b, described above.
[0093]
The infill wellbore 440 may be provided in the reservoir 403 during an early
stage, a mid-stage or a late stage of at least one of the gravity-drainage
processes that
occur during steps 302 and 304. For instance, in some embodiments, infill
wellbore 440
may be provided during an early stage of at least one of the gravity-drainage
processes
that occur during steps 302 and 304. In these embodiments, an infill cyclic
process can
be operated in the infill wellbore 440 while the gravity-drainage processes
that occur
during steps 302 and 304 at relatively higher pressure.
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[0094] In step 306, a single infill well 440 is drilled in the unswept
region 430
between the first and second gravity drainage chambers 420a, 420b. In some
embodiments, the infill well 440 is provided in the unswept region 430 at a
position that
is vertically offset from the first 400b and second 410b producer wells of the
first injector-
first producer well pair 400 and the second injector-second producer well pair
410,
respectively. For instance, as shown in Figure 4A, the infill well 440 may be
provided at
a position that is vertically offset from both of the first producer well 400b
of the first
injector-first producer well pair 400 and from the second producer well 410b
of the second
injector-second producer well pair 410 in a direction towards overburden 401
of the
reservoir 403. By providing the infill well 440 at a position that is
vertically offset from both
of the first producer well 400b and the second producer well 410b in a
direction towards
the overburden 401 of the reservoir 400, the cyclic process can be at least
partially gravity
driven in displacing the mobilized region 442 towards the producer wells 400b
and 410b.
[0095] At a fourth step 308, the infill well 440 is operated under a
cyclic process
utilizing a mobilizing fluid to form a mobilized region 442 of the infill well
440. In this step,
operating the infill well 440 includes injecting the mobilizing fluid into the
infill well 440 and
producing a mixture of the injected mobilizing fluid and bitumen from the
infill well 440.
Operation of the infill well 440 provide for the formation of the mobilized
region 442 around
the infill well and between the gravity drainage chambers 420a, 420b.
[0096] Infill well 440 is operated using a cyclic process to extract
petroleum
products (e.g. bitumen) in the unswept region 430 between the gravity drainage
chambers
420a and 420b. For instance, the cyclic process could be a pure solvent
process like
CSP, or a CSP-based process with the addition of steam, or a steam process
with solvent
addition such as LASER or a pure steam process such as a cyclic steam
stimulation
(CSS) process.
[0097] The cyclic process may start during an early stage or during a mid-
stage of
the gravity drainage processes that occur during steps 302 and 304. For
instance, as
shown in Figure 4A, the cyclic process may begin at an early stage of the
gravity drainage
processes, "early stage" being from startup of the gravity drainage process to
the steam
chamber reaching about halfway to the top of the reservoir. Further, the
cyclic process
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,
,
may begin at a mid-stage of the gravity drainage process, the mid-stage being
from when
the steam chambers reaches about halfway to the top of the reservoir to when
neighboring steam chambers (e.g. 420a, 420b) touch each other (i.e. are in
fluid
communication with each other). Alternatively, the cyclic process may start at
a late stage
of the gravity drainage processes that occur during steps 302 and 304. For
instance, as
shown in Figure 4B, the cyclic process may begin at a late stage of the
gravity drainage
processes when the gravity drainage chambers 420a, 420b are in communication
with
each other.
[0098] The mobilizing fluid may be a liquid or vapor solvent, a
solvent mixed with
steam, or pure steam. In embodiments where the mobilizing fluid includes a
solvent, the
solvent can be any solvent described above with respect to the solvents that
can be used
during the gravity drainage processes.
[0099] At a fifth step 310, the infill well 440 is operated under a
flooding process
utilizing a driving fluid to displace bitumen in the mobilized region 442
towards the first
and second producer wells 400b, 410b for collection. As shown in Figure 5, the
cyclic
process is transitioned into the flooding process when the mobilized region
442 is in
communication with the first and second producer wells 400b, 410b. During this
step 310,
the driving fluid is continuously injected into the infill well 440 and passes
through
apertures in the infill well 440 into the reservoir 403 to displace the
mobilized region 442
outwardly from the infill well 440 towards the producer wells 400b, 410b.
[0100] In some embodiments, the flooding process can be described
as being both
gravity and pressure driven when there is vertical offset between the infill
well 440 and
the first and second producer wells 400b, 410b (e.g. when the infill well 440
is positioned
between the first and second producer wells 400b, 410b and vertically offset
from the first
and second producer wells 400b, 410b in a direction towards the overburden
401).
[0101] The driving fluid may be a vapor solvent, a solvent mixed
with steam or pure
steam. In embodiments where the driving fluid includes a solvent, the solvent
can be any
solvent described above with respect to the solvents that can be used during
the gravity
drainage processes.
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[0102] According to some embodiments, when the flooding process starts,
steam
injection through the original injector wells (400a and 410a in Figures 4A and
4B) of the
well pairs may stop or may continue at a reduced flow rate. In some
embodiments, when
the flooding process starts, steam injection through the original injector
wells (400a and
410a in Figures 4A and 4B) of the well pairs may switch to injection of a non-
condensable
gas (NCG). The NCG could be methane, CO2, nitrogen, produced gas, flue gas, or
a
combination of thereof.
[0103] At a sixth step 312, the bitumen is recovered from the first
producer well
400b and the second producer well 410b.
[0104] In some embodiments, one or both wells of each of the first
injector-first
producer well pair 400 and the second injector-second producer well pair 410
may be
operated by a cyclic process before being operated by the first gravity
drainage process
and the second gravity drainage process, respectively. For clarity, each well
400a and
400b of pair 400 and each well 410a and 410b of pair 410 can be operated alone
or
together as a pair by the cyclic process. By operating one or both wells of
each of the first
injector-first producer well pair 400 and the second injector-second producer
well pair 410
by a cyclic process before each well pair 400, 410 being operated by the first
gravity
drainage process and the second gravity drainage process, respectively, a
start-up
process of the first and second gravity drainage processes may be improved. As
noted
above, cyclic processes such as a pure solvent process like CSP, or a CSP-
based
process with the addition of steam, or a steam process with solvent addition
such as
LASER or a pure steam process such as a cyclic steam stimulation (CSS) process
are
typically operated at higher pressures than gravity drainage processes like
SAGD.
Referring to Figure 6, operating one or both wells of each of the first
injector-first producer
well pair 400 and the second injector-second producer well pair 410 by a
cyclic process
before each well pair 400, 410 being operated by the first gravity drainage
process and
the second gravity drainage process, respectively, may lead to the formation
of a region
of mobilized fluid 425 around the injector wells 400a, 410a quicker than would
occur under
a strict gravity-drainage process.
- 20 -
CA 3027074 2018-12-11
[0105] According to some embodiments, the start-up of the first and
second gravity
drainage processes may be enhanced by starting with alew short cycles (e.g. up
to three
cycles) of a cyclic process to condition a near well region around the wells
400a, 400b,
410a and 410b, and also to accelerate initial production.
[0106] The cyclic process is operated at a pressure below a fracture
pressure of
the reservoir 403. In one example, a CSP using a light hydrocarbon solvent may
be
operated as the cyclic process. In another example, a low-pressure CSS or
LASER
process may also be operated as the cyclic process. In some examples, two or
three
cycles of a cyclic process may be operated in one or more of the wells 400a,
400b, 410a
and 410b prior to the gravity drainage process over a period of time ranging
from one
month to twelve months, during which the producer wells 400b and 410b may be
producing bitumen when not under injection
[0107] According to some embodiments, fluid distribution in the infill
well may be
better understood when the infill well is operated using a cyclic process by
understanding
steam/solvent vapor conformance in the gravity-drainage processes. Due to
geologic
heterogeneities, the steam/solvent vapor conformance is typically non-uniform
in the
gravity drainage processes, particular when employed in long (e.g. >800 metre)
horizontal
wells. An example of non-uniform conformance is shown by the shapes of the
gravity
drainage chambers 20a and 20b in Figure 2.
[0108] Referring now to Figure 7, in some embodiments, prior to drilling
the infill
well 740 between the two pairs of horizontal wellbores 700 and 710, an
understanding of
the chamber shape (e.g. chambers 720a and 720b) in the gravity drainage
processes
may be developed by applying 4D seismic or other surveillance techniques.
Based on a
mapped chamber shape, the infill well 740 may be completed with flow control
devices
(FCDs) 750 with different density and/or sizes along the infill well 740 to
control the
delivery of fluid into target regions. For example, fluid delivery may be
targeted to force
more fluid delivered into a bypassed region 760 where chambers 720a and 720b
do not
extend as close to the infill well 740 as they do in neighboring regions.
Forcing fluid into
regions such as a bypassed region 760 may improve the solvent utilization in
the cyclic
process and may also increase sweep efficiency and EUR in the infill well 740.
- 21 -
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,
[0109]
While the applicant's teachings described herein are in conjunction with
various embodiments for illustrative purposes, it is not intended that the
applicant's
teachings be limited to such embodiments as the embodiments described herein
are
intended to be examples. On the contrary, the applicant's teachings described
and
illustrated herein encompass various alternatives, modifications, and
equivalents, without
departing from the embodiments described herein, the general scope of which is
defined
in the appended claims.
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