U.S. patent application number 13/584333 was filed with the patent office on 2013-08-15 for methods and systems for in-situ extraction of bitumen.
This patent application is currently assigned to MARATHON OIL CANADA CORPORATION. The applicant listed for this patent is Mahendra Joshi, Julian Kift. Invention is credited to Mahendra Joshi, Julian Kift.
Application Number | 20130206405 13/584333 |
Document ID | / |
Family ID | 47711315 |
Filed Date | 2013-08-15 |
United States Patent
Application |
20130206405 |
Kind Code |
A1 |
Kift; Julian ; et
al. |
August 15, 2013 |
METHODS AND SYSTEMS FOR IN-SITU EXTRACTION OF BITUMEN
Abstract
Methods and systems for in situ extraction of bitumen from
deposits of bitumen-containing material are described. The methods
and systems can generally include establishing freeze walls within
the deposit of bitumen-containing material to establish a confined
zone into which solvents can be injected in order to extract
bitumen from the bitumen-containing deposits. Different types of
solvents can be sequentially injected in order to extract bitumen
and also help reduce the amount of solvent left behind in the
deposit.
Inventors: |
Kift; Julian; (Reno, NV)
; Joshi; Mahendra; (Katy, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kift; Julian
Joshi; Mahendra |
Reno
Katy |
NV
TX |
US
US |
|
|
Assignee: |
MARATHON OIL CANADA
CORPORATION
Calgary
CA
|
Family ID: |
47711315 |
Appl. No.: |
13/584333 |
Filed: |
August 13, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61522904 |
Aug 12, 2011 |
|
|
|
Current U.S.
Class: |
166/268 ;
166/279; 166/52 |
Current CPC
Class: |
E21B 43/16 20130101;
E21B 36/001 20130101; E21B 43/20 20130101; E21B 43/30 20130101 |
Class at
Publication: |
166/268 ;
166/279; 166/52 |
International
Class: |
E21B 43/20 20060101
E21B043/20; E21B 43/30 20060101 E21B043/30 |
Claims
1. A method of in-situ bitumen extraction comprising: forming one
or more vertical freeze walls within or around a deposit of
bituminous material and establishing a laterally confined deposit
of bituminous material; injecting a first solvent within the
laterally confined deposit of bituminous material; withdrawing a
mixture of dissolved bitumen and first solvent from within the
laterally confined deposit of bituminous material; injecting a
second solvent within the laterally confined deposit of bituminous
material; withdrawing a mixture of first solvent and second solvent
from within the laterally confined deposit of bituminous material;
injecting water within the laterally confined deposit of bituminous
material; and withdrawing a mixture of second solvent and water
from within the laterally confined deposit of bituminous
material.
2. The method as recited in claim 1, wherein the method further
comprises forming one or more horizontal freeze walls within the
deposit of bituminous material and vertically confining the
laterally confined deposit of bituminous material.
3. The method as recited in claim 1, wherein the one or more
vertical freeze walls abut an impervious geological material
located (within or) below the deposit of bituminous material.
4. The method as recited in claim 1, wherein forming one or more
vertical freeze walls within or around the deposit of bituminous
material comprises: drilling a plurality of spaced apart vertical
bores within or around the deposit of bituminous material; and
circulating a refrigerant through the vertical bores.
5. The method as recited in claim 1, wherein injecting the first
solvent within the laterally confined deposit of bituminous
material comprises: drilling one or more vertical injection bores
within the laterally confined deposit of bituminous material; and
injecting the first solvent within the laterally confined deposit
of bituminous material through the one or more vertical injection
bores.
6. The method as recited in claim 5, wherein withdrawing the
mixture of dissolved bitumen and first solvent from within the
laterally confined deposit of bituminous material comprises:
drilling one or more vertical production bores within the laterally
confined deposit of bituminous material; and withdrawing the
mixture of dissolved bitumen and first solvent from the laterally
confined deposit of bituminous material through the one or more
vertical production bores.
7. The method as recited in claim 1, wherein prior to injecting the
first solvent within the laterally confined deposit of bituminous
material, water is injected into the laterally confined deposit of
bituminous material.
8. The method as recited in claim 7, wherein the water comprises
steam.
9. The method as recited in claim 5, wherein injecting the second
solvent within the laterally confined deposit of bituminous
material comprises injecting the second solvent through the one or
more vertical injection bores.
10. The method as recited in claim 6, wherein withdrawing the
mixture of first solvent and second solvent from within the
laterally confined deposit of bituminous material comprises
withdrawing the mixture of first solvent and second solvent through
the one or more vertical production bores.
11. The method as recited in claim 5, wherein injecting water
within the laterally confined deposit of bituminous material
comprises injecting water through the one or more vertical
injection bores.
12. The method as recited in claim 6, wherein withdrawing the
mixture of second solvent and water from within the laterally
confined deposit of bituminous material comprises withdrawing the
mixture of second solvent and water through the one or more
vertical production bores.
13. The method as recited in claim 1, wherein the first solvent
comprises an aromatic solvent.
14. The method as recited in claim 1, wherein the second solvent
comprises a polar solvent.
15. The method as recited in claim 6, wherein: the one or more
vertical injection bores are arranged in a straight line; the one
or more vertical production bores are arranged in a straight line
parallel to and spaced a distance away from the straight line of
vertical injection bores; and the first solvent is injected into
the laterally confined deposit of bituminous material in a
direction towards the straight line of one or more vertical
production bores.
16. The method as recited in claim 1, further comprising:
separating the mixture of dissolved bitumen and first solvent
withdrawn from within the laterally confined deposit of bituminous
material into a bitumen stream and a first solvent stream; and
reusing the first solvent stream in the step of injecting first
solvent within the laterally confined deposit of bituminous
material.
17. A system for in-situ bitumen extraction comprising: a plurality
of vertical freeze wall bores formed in a deposit of bituminous
material and aligned in a geometric pattern; a refrigerant source
in fluid communication with the plurality of vertical freeze wall
bores; a plurality of vertical injection bores formed win the
deposit of bituminous material and located within the geometric
pattern of the plurality of freeze walls; a water source in fluid
communication with the plurality of vertical injection bores; a
solvent source in fluid communication with the plurality of
vertical injection bores; a second solvent source in fluid
communication with the plurality of vertical injection bores; and a
plurality of vertical production wells formed in the deposit of
bituminous material and located within the geometric pattern of the
plurality of freeze walls.
18. The system as recited in claim 17, further comprising: a
bitumen-first solvent separator in fluid communication with the
plurality of vertical production wells; a first solvent-second
solvent separator in fluid communication with the plurality of
vertical production wells; and a second solvent-water separator in
fluid communication with the plurality of vertical production
wells.
19. The system as recited in claim 17, wherein the plurality of
vertical freeze wall bores are in fluid communication with one
another.
20. The system as recited in claim 17, wherein the plurality of
vertical injection bores each comprises: an inner passage; a
co-annular outer passage separated from the inner passage by a
partition; a plurality of inner passage injection ports extending
from the inner passage to the exterior of the vertical injection
bore; and a plurality of outer passage injection ports extending to
the exterior of the vertical injection bore.
21. The system as recited in claim 20, wherein the inner passage is
in fluid communication with only the water source and the outer
passage is in fluid communication with only the first solvent
source and the second solvent source.
Description
[0001] This application claims priority to U.S. Provisional Patent
Application No. 61/522,904, filed Aug. 12, 2011, the entirety of
which is hereby incorporated by reference.
BACKGROUND
[0002] Deposits of bituminous material can be found throughout the
world, including in the United States and Canada. Depending on the
depth of the bituminous material, various methods can be used to
extract bitumen from bituminous deposits. When the bituminous
material is located relatively close to the surface, surface mining
can be used to remove the bituminous material from the ground.
However, deeper deposits of bituminous material cannot be
economically obtained through surface mining. Accordingly, methods
involving the use of well bores drilled into the bituminous
deposits have been developed.
[0003] One such method for obtaining deeper deposits of bituminous
material is the Steam Assisted Gravity Drainage (SAGD) method. The
SAGD method generally includes injecting steam into the bituminous
deposit to warm the bituminous material and make it flowable. Once
the viscosity of the bituminous material is sufficiently lowered,
the bituminous material can flow downwardly to a horizontal
production well that is positioned below the horizontal well used
to inject steam into the deposit. While the SAGD method can be
relatively effective in extracting bituminous material from bitumen
deposits, other methods that do not require the use of water and
that provide better bitumen extraction rates are desired.
[0004] The use of solvents to extract bitumen from mined oil sands
or the like is considered an effective method for separating
bitumen from other components of the oil sands material. The
solvent is generally used to dissolve the bitumen, after which the
bitumen-loaded solvent is separated from the sand, clay, and other
components of the oil sands. The injection of solvent into a
deposit of oil sands to dissolve the bitumen would appear to be an
effective means for extracting bitumen from a bituminous deposit,
but several problems are associated with solvent injection into the
ground that have prevented the method from being feasible.
[0005] One primary problem with injecting solvent into the oil
sands deposit is that it has been difficult or impossible to
recover a sufficient amount of the injected solvent to make the
process economical. For example, in some instances, only 25% of the
solvent injected into the deposit can be recovered. The cost of
having to replenish large amounts of solvent to continue the
process generally makes the process uneconomical.
[0006] An additional problem with injecting solvent into the oil
sands deposits relates to the environmental concerns of injecting
potentially hazardous solvent material into the ground without any
effective way of recovering the solvent or preventing the solvent
from migrating to a location outside of the oil sands deposit. For
example, if the oil sands deposit is near an aquifer, then concerns
arise regarding the flow of solvent out of the oils sands deposit
and into the aquifer, where potential well water would be
contaminated.
SUMMARY
[0007] The foregoing and other features, utilities and advantages
of the invention will be apparent from the following more
particular description of a preferred embodiment of the invention
as illustrated in the accompanying drawings.
[0008] In some embodiments, a method of in-situ bitumen extraction
is disclosed, the method including a step of forming one or more
vertical freeze walls within or around a deposit of bituminous
material and establishing a laterally confined deposit of
bituminous material; a step of injecting a first solvent within the
laterally confined deposit of bituminous material; a step of
withdrawing a mixture of dissolved bitumen and first solvent from
within the laterally confined deposit of bituminous material; a
step of injecting a second solvent within the laterally confined
deposit of bituminous material; a step of withdrawing a mixture of
first solvent and second solvent from within the laterally confined
deposit of bituminous material; a step of injecting water within
the laterally confined deposit of bituminous material; and a step
of withdrawing a mixture of second solvent and water from within
the laterally confined deposit of bituminous material.
[0009] In some embodiments, a system for in-situ bitumen extraction
is disclosed, the system including a plurality of vertical freeze
wall bores formed in a deposit of bituminous material and aligned
in a geometric pattern; a refrigerant source in fluid communication
with the plurality of vertical freeze wall bores; a plurality of
vertical injection bores formed win the deposit of bituminous
material and located within the geometric pattern of the plurality
of freeze walls; a water source in fluid communication with the
plurality of vertical injection bores; a first solvent source in
fluid communication with the plurality of vertical injection bores;
optionally a second solvent source in fluid communication with the
plurality of vertical injection bores; and a plurality of vertical
production wells formed in the deposit of bituminous material and
located within the geometric pattern of the plurality of freeze
walls.
[0010] The foregoing and other features and advantages of the
present application will become more apparent from the following
detailed description, which proceeds with reference to the
accompanying figures. In this regard, it is to be understood that
the scope of the invention is to be determined by the claims as
issued and not by whether given subject includes any or all
features or aspects noted in this Summary or addresses any issues
noted in the Background.
BRIEF DESCRIPTION OF THE DRAWING
[0011] The preferred and other embodiments are disclosed in
association with the accompanying drawings in which:
[0012] FIG. 1 is flow chart of embodiments of an in-situ bitumen
extraction method described herein;
[0013] FIG. 2 is an aerial view of a configuration of well bores
formed in a deposit of bituminous material in accordance with some
embodiments described herein;
[0014] FIG. 3 is an aerial view of a configuration of well bores
formed in a deposit of bituminous material, including a two loop
refrigerant circulation system according to some embodiments
described herein;
[0015] FIG. 4 is a cross-sectional view of a bituminous deposit
having a vertical injection well and a vertical production well
formed therein in accordance with some embodiments described
herein;
[0016] FIG. 5 is a cross-sectional view of a bituminous deposit
having a horizontal injection well and a horizontal production well
formed therein in accordance with some embodiments described
herein; and
[0017] FIG. 6 is a cross-sectional view of a composite injection
according to some embodiments described herein.
DETAILED DESCRIPTION
[0018] With reference to FIG. 1, some embodiments of a method of
in-situ extraction of bitumen generally include a step 100 of
forming one or more vertical freeze walls within or around a
deposit of bituminous material and establishing a laterally
confined deposit of bituminous material, a step 110 of injecting a
first solvent within the laterally confined deposit of bituminous
material, a step 120 of withdrawing a mixture of dissolved bitumen
and first solvent from within the laterally confined deposit of
bituminous material, a step 130 of injecting a second solvent
within the laterally confined deposit of bituminous material, a
step 140 of withdrawing a mixture of first solvent and second
solvent from within the laterally confined deposit of bituminous
material, a step 150 of injecting water within the laterally
confined deposit of bituminous material, and a step 160 of
withdrawing a mixture of second solvent and water from within the
laterally confined deposit of bituminous material. Such embodiments
can successfully confine material injected into the bituminous
deposit within a prescribed area. Similarly, mixtures of dissolved
bitumen and solvent created by injecting material into the
bituminous deposit are maintained within the area defined by the
freeze walls. Accordingly, contamination of, for example,
underground water sources can be mitigated or prevented and
recovery of dissolved bitumen can be enhanced by providing barriers
around the bitumen deposit being subjected to the bitumen
extraction processes.
[0019] In step 100, one or more vertical freeze walls are formed
within or around a deposit of bituminous material. The vertical
freeze walls formed within or around the deposit of bituminous
material form a boundary around all or a portion of the deposit of
bituminous material and establish a laterally confined deposit of
bituminous material. An objective of step 100 is to provide
vertical boundaries that will prevent material injected into the
deposit of bituminous material and mixture of materials formed
within the bituminous deposit from traveling outside of the
laterally confined area, thus alleviating environmental concerns of
in-situ bitumen extraction and making collection of dissolved
bitumen easier.
[0020] The deposit of bituminous material in which the vertical
freeze walls are formed in step 100 can be any suitable deposit of
bituminous material. Suitable deposits of bituminous material
include tar sands or oil sands formations, such as those located in
the Athabasca region of Canada. In some embodiments, the deposit of
bituminous material is a deposit or a portion for a deposit that is
located at a depth that is too deep for surface mining but too
shallow for traditional in-situ bitumen extraction methods such as
stream assisted gravity drainage (SAGD). In some embodiments, the
deposit of bituminous material is located at a depth of from
between 250 feet and 1,500 feet below the surface.
[0021] The one or more freeze walls formed in the deposit of
bituminous material can be any type of freeze wall capable of
slowing or preventing the movement of fluids through the freeze
wall. The freeze walls are typically made from water that is
naturally present in the ground in a liquid form. By freezing this
water, a barrier of ice is created in the ground. Freeze walls can
be formed in deposits of bituminous material because bituminous
material (such as oil sands deposits) typically includes a water
content.
[0022] Any manner of forming the one or more freeze walls known to
those of ordinary skill in the art can be used in the embodiments
of this method. In an exemplary method, a series of interconnected
vertical well bores are constructed within or around the deposit of
bituminous material, and a refrigerant is circulated through the
vertical well bores until the water in the ground proximate the
vertical well bores freezes. The refrigerant can be continuously
circulated through the vertical well bores to ensure the water
remains frozen and the freeze walls remain intact. Any suitable
refrigerant can be used, such as brine or ammonia. In some
embodiments, the refrigerant is circulated within the well bores
for a period of from 6 weeks to 16 weeks in order to establish the
freeze walls.
[0023] The arrangement and spacing of the vertical well bores
within or around the deposit of bituminous material can be any
suitable arrangement for providing freeze walls. In some
embodiments, the vertical well bores are spaced close enough
together that the water in the area between two adjacent vertical
well bores can be frozen to create a vertical freeze wall. In some
embodiments, the well bores are spaced apart approximately 2 to 6
meters from one another.
[0024] The dimensions of the well bores can vary based on the
specific application but are typically selected to ensure that a
suitable amount of refrigerant passes through the well bores to
freeze the water in the surrounding ground. In some embodiments,
the well bores have a diameter in the range of from 3 to 15 inches.
The depth of the well bores can be dependent on a variety of
factors. In some embodiments, the depth of the well bores is
selected based on the depth of the deposit of bituminous material
and/or the depth of any bed rock or other geological formation that
might be located beneath the deposit of bituminous material. A bed
rock or other geological formation below the deposit of bituminous
material can serve as a lower horizontal boundary for the deposit
of bituminous material, so it can be beneficial to extend the well
bores down to abut a rock formation or the like. Generally
speaking, the well bores will have a depth of from 100 to 1,500
feet.
[0025] In some embodiments, the vertical well bores are arranged in
a closed geometric pattern (when looking down at the vertical well
bores from above) to thereby create vertical freeze walls that
enclose a deposit of bituminous material. Any suitable closed
geometric shape can be used. With reference to FIG. 2, the vertical
well bores 200 are arranged in a rectangular shape, with each side
of the rectangle including several well bores 200. The well bores
200 are spaced close enough to freeze the area 210 between each
well bore 200 and ultimately form a series of vertical freeze walls
arranged in a rectangular shape and enclosing a deposit of
bituminous material 220.
[0026] The well bores used to form the freeze walls are generally
constructed by drilling vertical holes into the deposit of
bituminous material and providing piping within the drilled holes.
The piping can be any suitable type of piping, but is typically of
a type that is impermeable to fluids and has good heat transfer for
allowing the refrigerant to freeze the water proximate the piping.
The piping may also have structural additions to improve heat
transfer, such as a plurality of fins extending out from the
piping. As noted above, the piping provided in the drilled holes
can be interconnected with piping in adjacent drilled holes such
that the refrigerant can circulate throughout the plurality of well
bores.
[0027] In some embodiments, the well bores constructed for
establishing freeze walls in the deposit of bituminous material can
include a two loop system of interconnected well bores. The two
loop system allows for refrigerant to be supplied into the
interconnected well bores in a first loop and for refrigerant to be
removed from the interconnected well bores in a second loop. With
reference to FIG. 3, the two loop system 300 provides a first loop
310 where refrigerant is introduced into the system to flow through
the well bores 350 and create and/or maintain freeze walls. The
first loop 310 extends around the closed geometric arrangement of
well bores 350 and is in fluid communication 315 with each of the
well bores 350 such that refrigerant introduced into the first loop
310 can travel to each of the well bores 350 and provide
refrigerant into the well bores 350. The two loop system also
includes a second loop 320. Like first loop 310, second loop 320
extends around the closed geometric arrangement of well bores 350
and is in fluid communication 325 with each of the well bores 350.
Second loop 320 receives refrigerant that has flowed through the
well bores 350 and provides a path 360 for the refrigerant to leave
the system 300. In some embodiments, the first loop 310 will be in
fluid communication at a bottom end of each well bore 350 and the
second loop 320 will be in fluid communication with the top end of
each well bore 350 such that new refrigerant is introduced into
each well bore 350 at the bottom via the first loop 310 and then
exits the well bore 350 at the top via the second loop 320. The
opposite arrangement can also be used. The two loop system 300
provides a manner for fresh refrigerant to be introduced into the
system and for used refrigerant to be taken out of the system,
where it can be reconditioned and reinjected back into the well
bores 350.
[0028] Well bores as described above are not the only mechanism
that can be used to create the freeze walls in step 110. In some
embodiments, freeze walls can be formed using thermosyphons.
Thermosyphons generally include a fully enclosed system having a
low temperature fluid (such as liquid CO.sub.2, or ammonia)
circulating inside. Natural convection allows the liquid to pick up
heat from the bed rock at the bottom of the closed system below and
convert to a vapor. The vapor rises to the top of the system, where
cooling occurs (such as wind cooling via radiators) to convert the
vapor back to liquid. The cooled liquid drains back to the bottom
of the system, and the process repeats.
[0029] As noted above, bed rock or other geological formations can
be used to serve as a lower horizontal barrier of the confined
deposit of bituminous material. However, natural barriers may not
always be available. Accordingly, in some embodiments, steps can
also be taken to form a horizontal freeze wall that will serve as a
barrier that vertically confines the deposit of bituminous
material. Generally speaking, such a horizontal freeze wall will
extend up to or beyond the vertical freeze walls laterally
confining the deposit of bituminous material. It can also be
preferable to have the horizontal freeze wall abut the bottom end
of the vertical freeze walls. In this manner, the material injected
into the confined deposit of bituminous material will be prevented
from leaving the confined area in both a lateral direction and in a
downward direction.
[0030] Any suitable manner of forming horizontal freeze walls can
be used. In some embodiments, the manner of forming the horizontal
freeze wall is similar or identical to the manner in which the
vertical freeze walls are used. For example, directional drilling
techniques can be used to form a plurality of horizontal well bores
through which refrigerant can flow in order to freeze the water in
the ground between adjacent horizontal well bores.
[0031] In step 100, the vertical freeze walls formed serve to
laterally confine a deposit of bituminous material. When bed rock
(or other geological formation) or a horizontal freeze wall are
used in conjunction with the vertical freeze walls, a "bath tub"
configuration is provided that is capable of retaining liquid
material within the confined "bath tub" area. Accordingly, when
solvents are injected into the confined area of bituminous
material, the "bath tub" configuration mitigates or eliminates
concerns related to injected solvent drifting out of the area
undergoing bitumen extraction and into, for example, underground
water sources. Similarly, the "bath tub" configuration helps to
keep dissolved bitumen within a confined area, which helps make
withdrawing dissolved bitumen from the deposit of bituminous
material more effective and efficient.
[0032] In step 110, a first solvent is injected into the laterally
confined deposit of bituminous material. The injected first solvent
is injected to dissolve bitumen and create a dissolved bitumen (or
"disbit") phase within the deposit. Once dissolved, the mixture of
bitumen and solvent can be withdrawn from the deposit to thereby
extract bitumen.
[0033] The first solvent used in step 110 may include a hydrocarbon
solvent. Any hydrocarbon solvent or mixture of hydrocarbon solvents
that is capable of dissolving bitumen can be used. In some
embodiments, the hydrocarbon solvent is a hydrocarbon solvent that
does not result in asphaltene precipitation. The hydrocarbon
solvent or mixture of hydrocarbon solvents can be economical and
relatively easy to handle and store. The hydrocarbon solvent or
mixture of hydrocarbon solvents may also be generally compatible
with refinery operations.
[0034] In some embodiments, the first solvent is a light aromatic
solvent. The light aromatic solvent is an aromatic compound having
a boiling point temperature less than about 400.degree. C. at
atmospheric pressure. In some embodiments, the light aromatic
solvent used in the first mixing step is an aromatic having a
boiling point temperature in the range of from about 75.degree. C.
to about 350.degree. C. at atmospheric pressure, and more
specifically, in the range of from about 100.degree. C. to about
250.degree. C. at atmospheric pressure.
[0035] It should be appreciated that the light aromatic solvent
need not be 100% aromatic compounds. Instead, the light aromatic
solvent may include a mixture of aromatic and non-aromatic
compounds. For example, the first solvent can include greater than
zero to about 100 wt % aromatic compounds, such as approximately 10
wt % to 100 wt % aromatic compounds, or approximately 20 wt % to
100 wt % aromatic compounds.
[0036] Any of a number of suitable aromatic compounds may be used
as the first solvent. Examples of aromatic compounds that can be
used as the first solvent include benzene, toluene, xylene,
aromatic alcohols and combinations and derivatives thereof. The
first solvent can also include compositions, such as kerosene,
diesel (including biodiesel), light gas oil, light distillate,
commercial aromatic solvents such as Solvesso 100, Solvesso 150,
and Solvesso 200 (also known in the U.S.A. as Aromatic 100, 150,
and 200, including mainly C.sub.10-C.sub.11 aromatics, and produced
by ExxonMobil), and/or naphtha. In some embodiments, the first
solvent may have a boiling point temperature of approximately
75.degree. C. to 375.degree. C. Naphtha, for example, is
particularly effective at dissolving bitumen and is generally
compatible with refinery operations.
[0037] In some embodiments, a portion or all of the first solvent
is derived from bitumen recovered by the in-situ bitumen extraction
process described herein. The bitumen extracted by the process
described herein can be subjected to distillation processing to
separate a light end portion of the bitumen that is suitable for
use as a first solvent in the process described herein. In some
embodiments, the light end portion of the recovered bitumen is a
fraction of the bitumen having a boiling point temperature in the
range of up to 225.degree. C.
[0038] Any distillation methods capable of separating fractions of
bitumen material known to those of ordinary skill in the art can be
used, including the use of atmospheric or vacuum distillation
towers. In some embodiments, a make-up first solvent, such as any
of the above discussed first solvents, can be mixed with the light
end portion of the bitumen in order to provide a suitable amount of
first solvent for the process. Obtaining a portion or all of the
first solvent from the bitumen recovered by the in-situ bitumen
extraction process described herein can be useful in that the
process can become essentially self-sustainable. Additionally, use
of first solvent derived from the recovered bitumen can reduce or
eliminate environmental concerns associated with using
non-indigenous or commercial solvents.
[0039] In some embodiments, the first solvent suitable for use in
step 110 includes a bitumen content, and can therefore be
considered as disbit or dilbit. The first solvent having a bitumen
content may be solvent obtained from a step of solvent extraction
process performed on bituminous material, such as tar sands or oil
sands.
[0040] The amount of first solvent injected into the laterally
confined deposit of bituminous material can be any suitable amount
of first solvent needed for dissolving bitumen. In some
embodiments, the amount of solvent injected into the deposit of
bituminous material will depend on the quality of the deposit of
bituminous material (i.e., the bitumen content of the bituminous
material). Larger bitumen contents can require larger amounts of
first solvent to ensure as much bitumen as possible is dissolved
into a disbit phase. The amount of first solvent injected into the
deposit of bituminous material can also vary on the size of the
area being subjected to bitumen extraction. In some embodiments,
the amount of first solvent injected into the deposit ranges from
0.5:1 to 5:1.
[0041] In some embodiments, the desired amount of first solvent is
injected into the deposit of bituminous material and is then
allowed to stay in the deposit of bituminous material for a period
of time before production wells are used to remove any disbit
formed. Holding the first solvent into the deposit of bituminous
material allows for the first solvent to migrate to a larger area
and have sufficient time to dissolve the bitumen. In some
embodiments, the first solvent is held in the deposit of bituminous
material for a period of from 1 day to 1 month.
[0042] Any suitable technique for injecting solvent into the
laterally confined deposit of bituminous material can be used in
step 110. In some embodiments, one or more injection wells are
formed in the laterally confined area, which allows for solvent to
flow down and into the bituminous material bound by the freeze
walls. Once the solvent is injected into the confined deposit of
bituminous material, the solvent works to dissolve the bitumen and
create a disbit phase within the deposit of bituminous material.
The injection wells can be paired with production wells capable of
drawing the disbit phase out of the deposit of bituminous material
and up to the surface.
[0043] The injection wells can be any type of injection wells
suitable for injecting solvent into a deposit of bituminous
material, and can be constructed by any suitable technique used by
those or ordinary skill in the art to construct injection wells.
Similarly, production wells used to draw fluid material out of the
deposit of bituminous material (such as disbit) can be any suitable
type of production well and can be constructed by any suitable
technique for constructing production wells. In some embodiments,
the injection wells and productions wells are similar enough that
injection wells can be transformed into production wells with
minimal modifications.
[0044] The dimensions of the production wells and injection wells
can be any suitable dimensions needed to carry out the in-situ
bitumen extraction. The length of the injection wells and the
production wells will generally be equal to or slightly shorter
than the depth of the deposit of bituminous material. The diameter
of the injection wells and production wells can vary, and in some
embodiments, range from 6 to 12 inches.
[0045] With reference to FIG. 4, the injection wells formed in the
laterally confined area can be vertical injection wells 410 that
have a plurality of injection ports 415 located along the height of
the injection well 410 for injecting solvent into the deposit of
bituminous material 400 at various depths. The injection ports 415
are capable of injecting solvent into the deposit of bituminous
material 400, and in some cases will generally inject solvent into
the bituminous deposit 400 at a direction perpendicular to the
vertical injection well 410. The vertical injection wells 410 can
be paired with vertical production wells 430 that are spaced apart
a distance from the injection wells 410. In this manner, the
vertical production wells can collect the mixture of solvent and
dissolved bitumen produced upon injecting solvent into the deposit
of bituminous material 400.
[0046] With reference to FIG. 5, the injection wells formed in the
laterally confined area can also be a series of horizontal
injection wells 510. The horizontal injection wells 510 generally
have an L-shaped configuration that includes a vertical portion
510a and a horizontal portion 510b. Solvent travels down into the
deposit of bituminous material 500 via the vertical portion 510a
and is injected into the deposit of bituminous material 500 via the
horizontal portion 510b. In some embodiments, a plurality of
injection ports 515 are located along the length of the horizontal
portion 510b of the horizontal injection well 510 such that solvent
is injected into the deposit of bituminous material 500 at various
locations along the length of the horizontal portion 510b of the
horizontal injection well 510. In some embodiments, the injection
ports 515 are oriented to inject solvent upwardly into the
bituminous deposit 500. Horizontal production wells 530 can also be
included to withdraw the disbit formed upon the injection of
solvent into the deposit of bituminous material 500 via the
horizontal injection well 510. In some embodiments, the horizontal
production wells 530 have a vertical portion 530a and horizontal
portion 530b. The horizontal portion 530b can be located parallel
to and below the horizontal portion 510b of the horizontal
injection well 510. The disbit formed above the horizontal portion
510b flows downwardly where it collected in the horizontal portion
530b of the horizontal production well 530. The collected disbit is
then transported up the vertical portion 530a of the horizontal
production well 530 to the surface.
[0047] The injection wells and production wells are formed within
the area of bituminous material confined by the freeze walls
established in step 100. The arrangement of the plurality of
injection wells and production wells is generally not limited and
can include any arrangement that will provide for multiple solvent
injection locations and multiple disbit production locations.
Generally speaking, the injection wells and production wells are
located close enough to one another that the production wells can
receive the disbit created by injecting solvent into the deposit of
bituminous material via the injection wells. In some embodiments, a
production well is located from 50 to 100 feet from an injection
well.
[0048] In some embodiments, more injection wells than production
wells will be provided within the deposit of bituminous material
confined by the freeze walls, such as from 2 to 6 injection wells
per production well. The arrangement of injection wells and
production wells can include various geometric shapes and patterns.
One exemplary arrangement involves a hexagonal matrix of production
wells surrounding an injection well located in the middle of the
hexagon.
[0049] In some embodiments where vertical injection wells and
production wells are used, the arrangement of injection wells and
production wells can be a straight line arrangement of injection
wells and a straight line arrangement of production wells parallel
to the injection wells and spaced apart a suitable distance. The
straight lines of injection wells and production wells can be
located relatively close to one of the freeze walls making up the
boundary of the confined deposit of bituminous material, and can
also be oriented in parallel to that freeze wall. Thus, for
example, in a rectangular shaped confined deposit of bituminous
material, a straight line of injection wells can be located next to
and in parallel with a freeze wall, while a straight line of
production wells can be located next to and in parallel with the
straight line of injection wells, and further away from the freeze
wall then the injection wells. The injection ports on the injection
wells can be pointed in a direction towards the production wells
(i.e., away from the freeze wall) to extract bitumen from the area
closest to the freeze wall. Once this area has been sufficiently
treated, the injection wells can be decommissioned, the production
wells can be converted to injection wells (including positioning
injection ports in a direction away from the freeze wall), and a
new straight line of production wells can be formed further into
the confined area and in parallel with the straight line of
injection wells. The space between the new injection wells and the
new production wells can be treated for a sufficient period of
time, after which the above described process of converting
production wells into injection wells and forming new production
wells is repeated. This cycle can be repeated until the entire
length of the rectangular confined area is subjected to bitumen
extraction. Such a system can be referred to as a "line drive"
process of extracting bitumen.
[0050] In some embodiments, the injection of first solvent is
followed by an agitation step in order to promote mixing between
the solvent and the bituminous material. Any suitable manner of
causing agitation within the bituminous deposit can be used. In
some embodiments, the agitation step includes a gas injection or
gas pulsation step. In both gas injection and gas pulsation, the
introduction of the gas into the deposit leads to improved mixing
between the solvent and the bituminous material, which in turn
leads to more bitumen dissolving in the solvent.
[0051] The gas injection or gas pulsation step can be carried out
using the injection wells described in greater detail above. For
example, in gas injection, the gas is injected into the deposit via
the same injection wells used to inject the solvent into the
bituminous deposit. Any gas suitable for use in agitating the
solvent in the bituminous deposit can be used. In some embodiments,
the gas is unreactive to the materials in the bituminous deposit
such that the injection of the gas leads to primarily the
mechanical agitation of the solvent and not to the reaction between
the gas and the solvent or materials in the bituminous deposit.
Exemplary gasses that can be used include but are not limited to
natural gas, nitrogen, air, and carbon dioxide.
[0052] In some embodiments, the gas is preferably injected into the
bituminous deposit at relatively high volumes to ensure agitation.
In some embodiments, the gas is injected into the bituminous
deposit at a rate of 0.20 to 1.45 BCFD (depending on the geologic
conditions and oil production rate) or, in some embodiments, from
130 BOPD to 600 BOPD per MMCFD of gas injected. When gas pulsation
is used, the frequency of the gas pulsation can be between 2 and 10
Hz. The injection of first solvent into the bituminous deposit can
be carried out in several cycles, and in some embodiments, the
agitation step is carried out after every cycle of injecting first
solvent into the bituminous deposit.
[0053] In step 120, a mixture of first solvent and dissolved
bitumen produced from injecting solvent into the deposit of
bituminous material in step 110 is withdrawn from within the
laterally confined deposit of bituminous material. Any suitable
manner of withdrawing the disbit from within the deposit of
bituminous material can be used to carry out step 120. As discussed
in greater detail above, in some embodiments the disbit is
withdrawn from within the deposit of bituminous material using
production wells that are located proximate the injection wells.
Production wells can be operated for extended periods of time, such
as up to 9 months, to ensure that the vast majority of the disbit
produced in step 110 is withdrawn from the deposit. In some
embodiments, the production wells are operated until 90% of the
disbit produced in step 110 is removed. Step 120 is usually
performed after step 110 is completed, but is some embodiments,
step 120 can be commenced prior to step 110 being completed.
[0054] The fluid material withdrawn from within the deposit of
bituminous material in step 120 generally includes first solvent
and dissolved bitumen. Other materials that can be present in the
fluid material include water, and organic and inorganic solids.
Generally speaking, the fluid material withdrawn in step 120
includes from 40 to 75% first solvent, from 25 to 60% bitumen, from
0 to 5% water, and less than 2% other materials. The rate of
withdrawing the fluid material is generally not limited, and in
some embodiments, the fluid is withdrawn from within the deposit of
bituminous material via the production wells at a rate of from
about 5,000 to 25,000 bbls/day.
[0055] Once the mixture of dissolved bitumen and first solvent is
brought to the surface in step 120, various separation steps can
take place to separate the bitumen, first solvent, and water. Any
suitable separation unit or series of separation units can be used
to separate the bitumen, first solvent, and water, such as
distillation towers. Once separated, the bitumen can be further
processed, such as by being subjected to upgrading to produce
useful lighter hydrocarbons. The recovered first solvent can be
reused in the bitumen extraction process, such as by reusing the
first solvent in step 110.
[0056] Steps 110 and 120 described above can be repeated several
times prior to moving on to the injection of a second solvent.
Performing multiple cycles of injecting first solvent and
withdrawing a mixture of first solvent and bitumen can help to
improve the overall amount of bitumen recovered using the methods
described herein.
[0057] In some embodiments, step 120 will not be capable of
withdrawing all of the first solvent injected into the deposit of
bituminous material in step 110. For example, from 10 to 50% of the
first solvent injected into the deposit of bituminous material may
remain in the deposit after the completion of step 120. For
environmental and economical reasons, additional steps should be
taken to attempt to remove the first solvent from the deposit of
bituminous material.
[0058] In steps 130 and 140, a second solvent is injected into the
bituminous material to form a mixture of first solvent and second
solvent, and then the mixture of first solvent and second solvent
is withdrawn from the laterally confined deposit of bituminous
material. The second solvent is injected into the bituminous
material in an effort to mix with and/or displace the first
solvent. Injection of the second solvent can result in the second
solvent pushing the residual first solvent towards the production
wells, where the production wells can then be used to withdraw the
mixture of first solvent and second solvent. Additionally, the
second solvent may dissolve further bitumen not dissolved by the
first solvent, and therefore the injection of the second solvent
can also increase the bitumen extraction rate.
[0059] Any suitable solvent capable of mixing with and/or
displacing the first solvent can be used as the second solvent. In
some embodiments, the second solvent includes one or more aliphatic
compounds that are capable of solvating bitumen and/or the first
solvent. Suitable aliphatic compounds can include compounds such as
alkanes or alkenes. Any of these aliphatic compounds can be
functionalized or non-functionalized. In some embodiments, the
second solvent includes one or more aliphatic hydrocarbons having 3
to 5 carbon atoms. In some embodiments, the second solvent includes
aliphatic hydrocarbons having no more than 5 carbon atoms. The
second solvent can also include lower carbon paraffins, such as
cyclo- and iso-paraffins having 3 to 5 carbon atoms. Exemplary
second solvents include, but are nor limited to, methane, ethane,
propane, butane, and/or pentane, alkene equivalents of these
compounds and/or combinations and derivatives thereof.
[0060] In some embodiments, the second solvent is a polar solvent.
Any polar solvent capable of displacing the first solvent can be
used in step 130. In some embodiments, the polar solvent may be an
oxygenated hydrocarbon. Oxygenated hydrocarbons may include any
hydrocarbons having an oxygenated functional group. Oxygenated
hydrocarbons may include alcohols, ketones and ethers. Oxygenated
hydrocarbons as used in the present application do not include
alcohol ethers or glycol ethers.
[0061] Suitable alcohols for use as the polar solvent may include
methanol, ethanol, propanol, and butanol. The alcohol may be a
primary (e.g., ethanol), secondary (e.g., isopropyl alcohol) or
tertiary alcohol (e.g., tert-butyl alcohol).
[0062] As noted above, the polar solvent may also be a ketone.
Generally, ketones are a type of compound that contains a carbonyl
group (C.dbd.O) bonded to two other carbon atoms in the form:
R1(CO)R2. Neither of the substituents R1 and R2 may be equal to
hydrogen (H) (which would make the compound an aldehyde). A
carbonyl carbon bonded to two carbon atoms distinguishes ketones
from carboxylic acids, aldehydes, esters, amides, and other
oxygen-containing compounds. The double-bond of the carbonyl group
distinguishes ketones from alcohols and ethers. The simplest ketone
is acetone, CH3-CO--CH3 (systematically named propanone).
[0063] In some embodiments, the polar solvent is a polar solvent
that is miscible with the first solvent. By selecting a polar
solvent that is soluble in the first solvent (or in which the first
solvent is soluble), the polar solvent may form a homogenous
mixture with the first solvent. As some bitumen may be present in
the first solvent, the homogenous mixture may also include a
bitumen content. This homogenous mixture of polar solvent and first
solvent (and possibly bitumen) can then be withdrawn from the
deposit of bituminous material via the production wells to help
remove first solvent from the deposit.
[0064] The polar solvent or mixture of polar solvents can be
economical and relatively easy to handle and store. The polar
solvent or mixture of polar solvents may also be generally
compatible with refinery operations.
[0065] The polar solvent need not be 100% polar solvent, although
in some embodiments, the polar solvent is made up entirely of polar
solvent. The polar solvent may include a mixture of polar compounds
and non-polar compounds. However, in some embodiments, the polar
solvent used in step 130 includes more than about 50 wt % polar
solvent, and preferably more than about 70 wt % polar solvent.
[0066] In some embodiments, the second solvent is a mixture of
water and peroxide. Suitable peroxides for use as the second
solvent include those which produce oxygen micro-bubbles upon being
mixed with hydrocarbon liquids or solids. Exemplary peroxides
suitable for use as the second solvent include hydrogen peroxide,
peroxide salts, and any compounds capable of producing hydrogen
peroxide on decomposition in water (e.g., sodium percarbonate).
[0067] The presence of the peroxide in the water can help to remove
bitumen and bitumen-laden solvent. The peroxide accomplishes this
at least in part by altering surface conditions, such as reducing
interfacial tension between oil, water, and inorganic material of
the bituminous deposit (including rocks). Reduced interfacial
tension can, for example, help release bitumen from within pores in
the bituminous deposit. Exothermic heat release associated with the
use of the peroxides can also assist in removal of bitumen and
solvent due to the heat release decreasing the viscosity of the
bitumen and solvent. The decreased viscosity of these materials
improves flowability and drainage and ultimately makes the material
easier to recover.
[0068] The oxygen micro-bubbles formed from the mixing of peroxide
and hydrocarbon material can also be useful in stripping
hydrocarbon material such as bitumen from inorganic material (such
as sand) in the bituminous deposit. It is believed that the oil
stripped from the sand will form a film on the oxygen
micro-bubbles. The stripped bitumen material can then be recovered
in the same manner as other free bitumen in the bituminous deposit,
i.e., by injecting additional wash materials (solvents or water)
into the bituminous deposit to mix with the oxygen micro-bubbles
and carry the stripped bitumen out of the deposit via production
wells. The continuous injection of a second solvent including water
and peroxide will continue to produce the oxygen micro-bubbles
having bitumen films within the deposit of bituminous material and
provide additional free bitumen for recovery from subsequent in
situ wash cycles.
[0069] The ratio of peroxide to water injected into the deposit as
a second solvent can be any suitable ratio that provides for the
creation of oxygen micro-bubbles upon mixing with hydrocarbon
material. In some embodiments, a 10 to 60% concentration of
peroxide in water is provided.
[0070] The manner of injecting second solvent is similar or
identical to the manner in which the first solvent is injected into
the deposit of bituminous material. The same injection wells used
for injecting first solvent can be used to inject second solvent.
The amount of second solvent injected into the laterally confined
deposit of bituminous material can be any suitable amount of second
solvent needed for removing the first solvent. In some embodiments,
the amount of second solvent injected into the deposit of
bituminous material will depend on the amount of first solvent in
the deposit. The amount of second solvent injected into the deposit
of bituminous material can also vary on the size of the area being
subjected to bitumen extraction. In some embodiments, the amount of
second solvent injected into the deposit ranges from 5,000 to
25,000 bbls.
[0071] In some embodiments, the desired amount of second solvent is
injected into the deposit of bituminous material and is then
allowed to stay in the deposit of bituminous material for a period
of time before production wells are used to remove the mixture of
first solvent and second solvent. In some embodiments, the second
solvent is held in the deposit of bituminous material for a period
of from 1 day to 1 month.
[0072] The manner of withdrawing a mixture of first and second
solvent from within the deposit if bituminous material is similar
or identical to the manner in which the mixture of first solvent
and dissolved bitumen is withdrawn from the deposit of bituminous
material. The same production wells used to withdraw disbit from
the deposit can be used to withdraw a mixture of first and second
solvent from the deposit.
[0073] The fluid material withdrawn from within the deposit of
bituminous material in step 140 generally includes first solvent
and second solvent. Other materials that can be present in the
fluid material include water, bitumen, and organic and inorganic
solids. Generally speaking, the fluid material withdrawn in step
140 includes from 40 to 75% first solvent, from 0 to 80% second
solvent, from 0 to 5% water, from 25 to 60% bitumen, and less than
2% other materials. The constituency of the fluid withdrawn in step
140 can also change over time as the second solvent reaches the
well head. The rate of withdrawing the fluid material is generally
not limited, and in some embodiments, the fluid is withdrawn from
within the deposit of bituminous material via the production wells
at a rate of from about 5,000 to 25,000 bbls/day.
[0074] Once the mixture of first solvent and second solvent is
brought to the surface in step 140, various separation steps can
take place to separate the first solvent from the second solvent.
Any suitable separation unit or series of separation units can be
used to separate the first solvent from the second solvent. Once
separated, the first solvent and the second solvent can both be
reused in the extraction process, with the first solvent reused in
step 110 and the second solvent reused in step 130.
[0075] As with steps 110 and 120, steps 130 and 140 can be carried
out multiple times in order to improve bitumen extraction and
solvent recovery rates. Also, step 130 can be followed by an
agitation step similar or identical to the agitation step performed
after step 110 as described in greater detail above. Thus, in some
embodiments, each time second solvent is injected into the
bituminous deposit, a gas injection or gas pulsation step can be
carried out in order to promote mixing between the injected second
solvent and the residual first solvent and bitumen located in the
bituminous deposit.
[0076] In some embodiments, step 140 will not be capable of
withdrawing all of the second solvent injected into the deposit of
bituminous material in step 130. For example, from 10 to 50% of the
second solvent injected into the deposit of bituminous material may
remain in the deposit after the completion of step 140. For
environmental and economical reasons, additional steps should be
taken to attempt to remove the second solvent from the deposit of
bituminous material.
[0077] In steps 150 and 160, water is injected into the bituminous
material to displace the residual second solvent towards the
production wells, where the second solvent and water may then be
withdrawn from the laterally confined deposit of bituminous
material. In embodiments where the second solvent is a polar
solvent, the injection of water is especially useful at displacing
the second solvent towards the production wells due to the
difference in polarity between the polar solvent and water. The
water injected into the deposit can be in the form of steam or as
liquid water.
[0078] The manner of injecting water is similar or identical to the
manner in which the first solvent and second solvent is injected
into the deposit of bituminous material. The same injection wells
used for injecting first solvent and second solvent can be used to
inject water. The amount of water injected into the laterally
confined deposit of bituminous material can be any suitable amount
of water needed for removing the second solvent. In some
embodiments, the amount of water injected into the deposit of
bituminous material will depend on the amount of second solvent in
the deposit. The amount of water injected into the deposit of
bituminous material can also vary based on the size of the area
being subjected to bitumen extraction. In some embodiments, the
amount of water injected into the deposit ranges from 3:1 to 10:1
on a water:bitumen ratio.
[0079] In some embodiments, the desired amount of water is injected
into the deposit of bituminous material and is then allowed to stay
in the deposit of bituminous material for a period of time before
production wells are used to remove the mixture of water and second
solvent. In some embodiments, the water is held in the deposit of
bituminous material for a period of from 1 day to 1 month.
[0080] In some embodiments, the water can include peroxide in order
to improve the solvent and bitumen recovery. Any suitable peroxide
can be added to the water used in step 150, including but not
limited to, hydrogen peroxide. In some embodiments, the amount of
peroxide included in the water used in step 150 is 10 to 60%.
[0081] The addition of peroxide to the water is considered
beneficial for two reasons. Firstly, the peroxide improves the
removal of residual solvent form within the bituminous deposit. As
discussed above, this is due at least in part to the peroxide
reducing interfacial tension between hydrocarbon material, water,
and inorganic material. Secondly, the peroxide is believed to
reduce the viscosity of bitumen, which improves the drainage of the
bitumen from the deposit via the production wells. Peroxides are
believed to reduce the viscosity of bitumen by oxidizing the sulfur
contained in the bitumen.
[0082] The use of peroxides to improve solvent and bitumen removal
from the bituminous deposit is also beneficial because the peroxide
does not leave behind harmful residual chemicals in the deposit.
For example, when hydrogen peroxide is used in the water wash, the
hydrogen peroxide will break down to oxygen and water.
[0083] The manner of withdrawing a mixture of water and second
solvent from within the deposit if bituminous material is similar
or identical to the manner in which the mixture of first solvent
and dissolved bitumen and the mixture of first solvent and second
solvent is withdrawn from the deposit of bituminous material. The
same production wells used to withdraw disbit and mixtures of first
and second solvent from the deposit can be used to withdraw a
mixture of water and second solvent from the deposit.
[0084] The fluid material withdrawn from within the deposit of
bituminous material in step 160 generally includes water and second
solvent. Other materials that can be present in the fluid material
include water, bitumen, and organic and inorganic solids. Generally
speaking, the fluid material withdrawn in step 160 includes from 40
to 90% water, from 60 to 95% second solvent, from 2 to 10% first
solvent, from 2 to 10% bitumen, and less than 2% other materials.
The constituency of the fluid withdrawn in step 160 can change over
time as the injected water reaches the well head. The rate of
withdrawing the fluid material is generally not limited, and in
some embodiments, the fluid is withdrawn from within the deposit of
bituminous material via the production wells at a rate of from
about 500 to 2,000 bbls/day per well head (by gravity
drainage).
[0085] Once the mixture of water and second solvent is brought to
the surface in step 160, various separation steps can take place to
separate the water solvent from the second solvent. Any suitable
separation unit or series of separation units can be used to
separate the water from the second solvent. In embodiments where
the second solvent is polar solvent, separation may occur naturally
or with minimal effort due to the difference in polarity. Once
separated, the second solvent can be reused in the extraction
process.
[0086] Any water left in the deposit of bituminous material can
remain in the deposit, as the water is not an environmental
concern. In some embodiments, 5 to 50% of the water injected into
the deposit in step 150 will remain in the deposit.
[0087] The above described method can be performed one or more
times on a confined deposit of bituminous material. Similarly, any
one step or pairs of steps (e.g., step 110 and 120) can be repeated
multiple times before moving on to the next step of the method.
Repeating certain steps of pairs of steps may help to increase the
bitumen extraction efficiency.
[0088] Once a confined deposit of bituminous material has been
subjected to the above-described in-situ bitumen extraction
process, the same process can be carried out on adjacent deposits
of bituminous material. In some embodiments, one or more freeze
walls established for carrying out the in-situ bitumen extraction
process on a first deposit of bituminous material can be re-used
when confining an adjoining deposit of bituminous material. For
example, when a confined deposit of bituminous material has a
square shape, three of the freeze walls can be decommissioned while
a fourth wall can be used as the first wall of a new confined
deposit of bituminous material located next to the first
deposit.
[0089] Additional pretreatment steps can also be carried out prior
to or during the method described above. For example, any of a
variety of fracturing steps or method to increase porosity can be
carried out prior to any of the solvent injection steps in an
attempt to create more passageways for solvent and other materials
to pass through.
[0090] Additionally, hot water or sloppy steam can be injected into
the deposit of bituminous material prior to or during the injection
of the first solvent in an effort to soften the oil sands and the
bitumen component or create channels for the subsequently injected
solvent to pass through. In some embodiments, the injection wells
can be adapted to allow for the simultaneous injection of water and
solvent through the same injection wells. The injection wells can
be "composite" injection wells that include multiple passage ways
within the same general piping. With reference to FIG. 6, a
composite injection well 600 can include a co-annular inner passage
610 and a co-annular outer passage 620, with the inner passage 610
having injection ports 615 that extend through the outer passage to
the exterior of the injection well 600. In this manner, steam or
water can travel down the inner passage 610 of the injection well
600 and be injected into the deposit at the same time that solvent
passes down the outer passage 620 of the injection well 600 and is
injected into the deposit through standard injection ports 625 in
fluid communication with the outer passage 620.
[0091] The majority of the system used to carry out the in-situ
bitumen extraction methods described herein is discussed above,
including the vertical freeze walls, the optional horizontal freeze
wall, the plurality of injection bores, and the plurality of
production wells. Also discussed above are the separation units
that can be provided, including the separator for separating disbit
into bitumen and solvent, the separator for separating a mixture of
first solvent and second solvent, a separator for separating a
mixture of second solvent and water, and distillation units for
producing solvent from recovered bitumen.
[0092] Additional components that can be part of the system include
a refrigerant source, a first solvent source, a water source, and a
second solvent source. Each source can include any type of supply
vessel that is capable of supplying the desired fluid needed for
the method. The supply vessels may also include recycle inputs for
receiving fluid material that is recovered from the process and
sent back into the system. The refrigerant source is in fluid
communication with the interconnected well bores used to establish
the freeze walls and, when a two loop system as described above is
used, can include a recycle input for receiving refrigerant that
has passed through the two loop system back into the refrigerant
source for storage and further use. The first solvent and water
sources can be in fluid communication with the outer and inner
passage of a composite injection well, respectively. Additionally,
the second solvent source can be in fluid communication with the
injection well.
[0093] While the invention has been particularly shown and
described with reference to a preferred embodiment thereof, it will
be understood by those skilled in the art that various other
changes in the form and details may be made without departing from
the spirit and scope of the invention.
[0094] A presently preferred embodiment of the present invention
and many of its improvements have been described with a degree of
particularity. It should be understood that this description has
been made by way of example, and that the invention is defined by
the scope of the following claims.
* * * * *