U.S. patent application number 14/446524 was filed with the patent office on 2015-02-05 for steam generation with carbon dioxide recycle.
The applicant listed for this patent is CONOCOPHILLIPS COMPANY. Invention is credited to David LARKIN, Scott MACADAM, James SEABA.
Application Number | 20150034322 14/446524 |
Document ID | / |
Family ID | 52426605 |
Filed Date | 2015-02-05 |
United States Patent
Application |
20150034322 |
Kind Code |
A1 |
MACADAM; Scott ; et
al. |
February 5, 2015 |
STEAM GENERATION WITH CARBON DIOXIDE RECYCLE
Abstract
Systems and methods relate to recovering hydrocarbons by
injecting into a reservoir steam along with carbon dioxide
recovered from flue gases produced while generating the steam and
from separation of produced fluids. Due to benefits from the carbon
dioxide injection, carbon dioxide capture rates from the flue gases
selected below fifty percent in such combined recovery of the
carbon dioxide enables lower fuel consumption even given that
additional fuel is needed for the carbon dioxide capture versus
steam only operations. As the capture rates from the flue gases
increase above fifty percent like when employed for sequestration
purposes, such approaches use more fuel than the steam only
operations and may not be cost efficient. A carbon dioxide recovery
unit coupled to an air-fired boiler or an auxiliary oxy-fired
boiler may supply the carbon dioxide recovered from the flue
gases.
Inventors: |
MACADAM; Scott; (Calgary,
CA) ; SEABA; James; (Calgary, CA) ; LARKIN;
David; (Tulsa, OK) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CONOCOPHILLIPS COMPANY |
Houston |
TX |
US |
|
|
Family ID: |
52426605 |
Appl. No.: |
14/446524 |
Filed: |
July 30, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61862309 |
Aug 5, 2013 |
|
|
|
Current U.S.
Class: |
166/305.1 ;
166/52 |
Current CPC
Class: |
E21B 43/2408
20130101 |
Class at
Publication: |
166/305.1 ;
166/52 |
International
Class: |
E21B 43/24 20060101
E21B043/24; E21B 43/16 20060101 E21B043/16 |
Claims
1. A method of recovering hydrocarbons with steam, comprising:
generating the steam with combustion to heat and vaporize water;
injecting into a formation the steam and carbon dioxide; producing
a mixture including the hydrocarbons, condensate of the steam and a
portion of the carbon dioxide; and supplying flow of the carbon
dioxide for sustaining the injecting by recovering the carbon
dioxide from the mixture produced and capturing less than 50
percent of carbon dioxide content within exhaust from the
combustion.
2. The method of claim 1, wherein the steam is generated in an
air-fired steam generator and the carbon dioxide content within the
exhaust is separated from other gases of the exhaust.
3. The method of claim 1, wherein the steam is generated in an
air-fired steam generator and the carbon dioxide content within the
exhaust is separated from other gases of the exhaust such that the
carbon dioxide injected is mixed with less than 10 percent nitrogen
by mass.
4. The method of claim 1, wherein an amine based absorption unit
captures the carbon dioxide content within the exhaust.
5. The method of claim 1, wherein the steam is generated in an
air-fired steam generator in which the carbon dioxide content in
the exhaust thereof is released and an oxy-fired steam generator in
which the carbon dioxide content in the exhaust thereof is used in
the supplying of the flow of the carbon dioxide.
6. The method of claim 1, wherein the carbon dioxide is injected
with the steam and at a rate between 1 and 25 percent of the steam
by mass.
7. The method of claim 1, wherein the carbon dioxide that is
injected is mixed with less than 10 percent nitrogen by mass.
8. The method of claim 1, wherein the steam is generated in a once
through steam generator.
9. The method of claim 1, wherein the injecting is into a well
disposed in the formation for a steam assisted gravity drainage
operation.
10. The method of claim 1, wherein less than 32 percent of the
carbon dioxide content within the exhaust from the combustion is
captured and a remainder is released to atmosphere.
11. A method of recovering hydrocarbons with steam, comprising:
producing the steam in an air-fired steam generator; injecting into
a formation the steam and carbon dioxide that is injected at a rate
between 1 and 25 percent of the steam by mass and is recovered from
production fluids and separated from other exhaust constituents of
the steam generator such that capture of carbon dioxide content
within exhaust from the steam generator is relied on to maintain
the rate given retention of a portion of the carbon dioxide in the
reservoir; and recovering the production fluids including the
hydrocarbons.
12. The method of claim 11, wherein the carbon dioxide is separated
from the other exhaust constituents of the steam generator to
provide the carbon dioxide mixed with less than 10 percent nitrogen
by mass.
13. The method of claim 11, wherein the carbon dioxide is separated
from the other exhaust constituents of the steam generator with an
amine based absorption unit.
14. The method of claim 11, wherein the carbon dioxide that is
separated from the other exhaust constituents of the steam
generator captures less than 50 percent of carbon dioxide content
within the exhaust of the steam generator.
15. The method of claim 1, wherein up to 16 percent of the carbon
dioxide content within the exhaust from the combustion is captured
and a remainder is released to atmosphere.
16. A system for recovering hydrocarbons with steam, comprising: a
steam generator that heats water with combustion to produce the
steam; at least one injection well coupled to the steam generator
for introducing the steam and carbon dioxide into a formation; at
least one production well to recover from the formation a mixture
including the hydrocarbons, condensate of the steam and a portion
of the carbon dioxide; and a carbon dioxide supply coupled to the
at least one injection well for providing the carbon dioxide that
is recovered from the mixture produced and captured from less than
50 percent of carbon dioxide content within exhaust from the
combustion.
17. The system of claim 16, wherein the steam generator includes an
air-fired steam generator in which the carbon dioxide content in
the exhaust thereof is released and an oxy-fired steam generator in
which the carbon dioxide content in the exhaust thereof forms part
of the carbon dioxide supply.
18. The system of claim 16, wherein the carbon dioxide supply
includes an amine based absorption unit to capture the carbon
dioxide content within the exhaust.
19. The system of claim 16, wherein the steam generator is a once
through steam generator.
20. The system of claim 16, wherein the injection well and the
production well form a steam assisted gravity drainage well pair.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a non-provisional application which
claims benefit under 35 USC .sctn.119(e) to U.S. Provisional
Application Ser. No. 61/862,309 filed Aug. 5, 2013, entitled "STEAM
GENERATION WITH CARBON DIOXIDE RECYCLE," which is incorporated
herein in its entirety.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
[0002] None
FIELD OF THE INVENTION
[0003] Embodiments of the invention relate to methods and systems
of producing a fluid of steam and carbon dioxide for injection into
a reservoir to facilitate oil recovery.
BACKGROUND OF THE INVENTION
[0004] Enhanced oil recovery processes employ thermal methods to
improve recovery of heavy oils from subsurface reservoirs. For
example, injection of steam into heavy oil bearing formations heats
the oil in the reservoir, which reduces the viscosity of the oil
and allows the oil to flow to a collection well. A mixture of the
oil and produced water that flows to the collection well is
recovered to the surface where the oil is separated from the
water.
[0005] Different approaches exist for generating the steam. Prior
once through steam generators (OTSGs) produce a wet steam by a
single pass of water through a boiler isolated from fluid
communication with combustion used to heat the boiler. An
alternative approach utilizes a direct steam generator (DSG) to
produce steam by contacting water with products from oxy-fuel
combustion.
[0006] Effluent from the DSG thus includes carbon dioxide along
with the steam from water vaporization and the combustion to limit
water replenishing requirements. The carbon dioxide may enhance
hydrocarbon recovery and provide another advantage over the OTSG.
However, the DSG can only provide a narrow range of carbon dioxide
concentrations and other ranges may be more effective.
[0007] Therefore, a need exists for systems and methods that are
cost efficient to generate steam with desired concentrations of
carbon dioxide.
SUMMARY OF THE INVENTION
[0008] In one embodiment, a method of recovering hydrocarbons with
steam includes generating the steam with combustion to heat and
vaporize water and injecting into a formation the steam and carbon
dioxide. The method further includes producing a mixture including
the hydrocarbons, condensate of the steam and a portion of the
carbon dioxide. Supplying flow of the carbon dioxide sustains the
injecting by recovering the carbon dioxide from the mixture
produced and capturing less than 50 percent of carbon dioxide
content within exhaust from the combustion.
[0009] According to one embodiment, a method of recovering
hydrocarbons with steam includes producing the steam in an
air-fired steam generator and injecting into a formation the steam
and carbon dioxide that is injected at a rate between 1 and 25
percent of the steam by mass and is recovered from production
fluids and separated from other exhaust constituents of the steam
generator. Capture of carbon dioxide content within exhaust from
the steam generator is relied on to maintain the rate given
retention of a portion of the carbon dioxide in the reservoir. In
addition, the method includes recovering the production fluids
including the hydrocarbons.
[0010] For one embodiment, a system for recovering hydrocarbons
with steam includes a steam generator that heats water with
combustion to produce the steam. At least one injection well
couples to the steam generator for introducing the steam and carbon
dioxide into a formation while at least one production well
recovers from the formation a mixture including the hydrocarbons,
condensate of the steam and a portion of the carbon dioxide. A
carbon dioxide supply couples to the at least one injection well
for providing the carbon dioxide that is recovered from the mixture
produced and captured from less than 50 percent of carbon dioxide
content within exhaust from the combustion.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] A more complete understanding of the present invention and
benefits thereof may be acquired by referring to the following
description taken in conjunction with the accompanying
drawings.
[0012] FIG. 1 depicts a schematic of a hydrocarbon recovery system
including a steam generator with flue gas exhaust coupled to a
carbon dioxide recovery unit for injection of steam and carbon
dioxide both from the recovery unit and separated from recovered
production fluids, according to one embodiment of the
invention.
[0013] FIG. 2 depicts a schematic of a hydrocarbon recovery system
including an oxy-fired boiler and an exhausted steam generator for
injection of steam and carbon dioxide both from flue gas exhaust of
the oxy-fired boiler and separated from recovered production
fluids, according to one embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0014] Embodiments of the invention relate to systems and methods
of recovering hydrocarbons by injecting into a reservoir steam
along with carbon dioxide recovered from flue gases produced while
generating the steam and from separation of produced fluids. Due to
benefits from the carbon dioxide injection, carbon dioxide capture
rates from the flue gases selected below fifty percent in such
combined recovery of the carbon dioxide enables lower fuel
consumption even given that additional fuel is needed for the
carbon dioxide capture versus steam only operations. As the capture
rates from the flue gases increase above fifty percent like when
employed for sequestration purposes, such approaches use more fuel
than the steam only operations and may not be cost efficient. A
carbon dioxide recovery unit coupled to an air-fired boiler or an
auxiliary oxy-fired boiler may supply the carbon dioxide recovered
from the flue gases.
[0015] FIG. 1 illustrates a system for recovering hydrocarbons that
includes a processing unit 102, an air-fired steam generator 116
and a carbon dioxide (CO2) recovery unit 110 that are all coupled
to at least one production well 100 and at least one injection well
124. In an exemplary embodiment, the injection well 124 and the
production well 100 provide a well pair for a steam assisted
gravity drainage (SAGD) operation. Various other recovery
operations including cyclic steam stimulation, solvent aided SAGD
and steam drive may also employ processes described herein.
[0016] In operation, the processing unit 102 receives a mixture
that is recovered from the production well 100 and includes
hydrocarbons or oil, condensate from steam that is injected to heat
and mobilize the oil and some carbon dioxide injected with the
steam. The processing unit 102 may include liquid-gas separators,
water-oil separators, treatment equipment for gas and water, and
compression equipment for gas. The processing unit 102 separates
the mixture into a sales stream 104 of the oil, a steam generator
feed stream 106 of water and a gas recycle stream 108 of the carbon
dioxide. The gas recycle stream 108 conveys the carbon dioxide that
is recovered in the processing unit 102 back to the injection well
124 for introducing into the formation.
[0017] Recovery of the carbon dioxide from produced fluids at the
processing unit 102 costs less than recovering the carbon dioxide
in flue streams that are majority nitrogen or providing an air
separation unit for oxy-combustion to limit the nitrogen in such
flue streams. In some embodiments, at least 90, 95, 99 or 100
percent of the carbon dioxide in the produced fluids is recycled
for injection into the formation. Embodiments described herein thus
utilize the carbon dioxide recovered from the produced fluids along
with the carbon dioxide recovered at rates less than fifty percent
of total carbon dioxide output from generation of the steam that is
injected. In contrast to other approaches that produce carbon
dioxide for offsite sequestration, such partial capture makes up
for reservoir retention to maintain a desired carbon dioxide
injection rate without requiring excess additional capture.
[0018] The steam generator 116 burns fuel, such as natural gas, in
air to heat and vaporize the water input via the feed stream 106.
Exhaust combustion gases exit from the steam generator 116 separate
from a steam output 122 that conveys resulting vaporized water to
the injection well 124. A boiler or once through steam generator
(OTSG) may provide the steam generator 116.
[0019] At least part of the combustion gases from the steam
generator 116 pass to the CO2 recovery unit 110. A concentrated
carbon dioxide stream 114 exits the CO2 recovery unit 110 and is
conveyed to the injection well 124 for injection with the steam
output 122. In some embodiments, the carbon dioxide stream 114
contains at least 90 percent, 95 percent or 99 percent carbon
dioxide by mass.
[0020] How much of the combustion gases that are diverted and/or
sizing of the CO2 recovery unit 110 depends on both retention rate
of the carbon dioxide in the reservoir and desired carbon dioxide
injection concentration rather than selection for maximizing carbon
dioxide emission avoidance. Increases in the retention rate of the
carbon dioxide in the reservoir reduce the amount of the carbon
dioxide produced and available for recycle, thereby requiring a
higher capture in the CO2 recovery unit 110 for a given desired
carbon dioxide injection concentration. Similarly, increasing the
desired carbon dioxide injection concentration also raises amount
of capture required in the CO2 recovery unit 110. In some
embodiments, level of the carbon dioxide in injected fluids may
range between 1 percent and 25 percent, greater than 15 percent or
less than 5 percent of the steam by mass with the fluids including
the steam and less than 10, 5 or 1 percent by mass other gases.
[0021] By way of example, the CO2 recovery unit 110 may utilize a
selective amine solution to strip the carbon dioxide from other
flue gas constituents by absorption of the carbon dioxide within
the solution. The amine solution comes in direct contact with the
combustion gases from the steam generator 116 in an absorber of the
CO2 recovery unit 110. The other flue gas constituents pass through
the absorber and may exit the CO2 recovery unit 110 as treated
exhaust via a discharge that opens to the atmosphere.
[0022] Ethanolamine(s) and/or other suitable solvents may be used
for the absorber solutions in some embodiments. Once the amine
solution has been used to separate the carbon dioxide, the amine
solution can be regenerated in a regenerator of the CO2 recovery
unit 110. For some embodiments, liberation of the carbon dioxide
from the amine solution may occur with temperature increase and
pressure reduction.
[0023] FIG. 2 shows an alternative hydrocarbon recovery system
including an oxy-fired boiler 216 to provide makeup carbon dioxide
within flue gas output 214 instead of utilizing the CO2 recovery
unit 110 in FIG. 1. Combustion exhaust from the air-fired steam
generator 116 may therefore release to the atmosphere. Other
components identified in FIG. 2 by like reference numbers to those
identified in FIG. 1 operate as described already herein.
[0024] In contrast to the air-fired steam generator 116, the
oxy-fired steam generator 216 burns fuel, such as natural gas or
methane, in oxygen to heat and vaporize the water input via the
feed stream 106. An air separation unit (ASU) may supply the oxygen
to the oxy-fired steam generator 216. The flue gas output 214 from
the oxy-fired steam generator 216 thus outputs carbon dioxide and
additional steam as products of combustion with less than 10, 5 or
1 percent other gases by mass conveyed to the injection well 124
separate from an auxiliary steam output 222 from the oxy-fired
steam generator 216 that also conveys resulting vaporized water to
the injection well 124.
[0025] Similar to sizing of the CO2 recovery unit 110, sizing of
the oxy-fired steam generator 216 depends on both retention rate of
the carbon dioxide in the reservoir and desired carbon dioxide
injection concentration rather than selection for maximizing carbon
dioxide emission avoidance. Increases in the retention rate of the
carbon dioxide in the reservoir reduce the amount of the carbon
dioxide produced and available for recycle, thereby requiring an
increase in the production rate of the oxy-fired steam generator
216 relative to the air-fired steam generator 116 for a given
desired carbon dioxide injection concentration. Similarly,
increasing the desired carbon dioxide injection concentration also
raises the production rate of the oxy-fired steam generator 216
relative to the air-fired steam generator 116.
[0026] Mixing of the steam output 122 and the recycle stream 108
with the carbon dioxide stream 114 from the CO2 recovery unit 110
or the flue gas output 214 of the oxy-fired steam generator 216
enables adjusting concentration range of carbon dioxide being
injected. Such control of the carbon dioxide concentration in the
steam being injected provides flexibility. For example, a
production profile may call for a lower carbon dioxide injection
concentration in early production stages and more in later stages,
which may be accomplished by increasing over time the amount of the
carbon dioxide sent to the injection well 124 via the recycle
stream 108.
[0027] As shown in the following table, process modeling compared
results associated with a steam only case and two exemplary cases
(e.g., as shown in FIG. 1) all for a 90,000 barrel per day SAGD
facility having all electrical power generated by a natural
gas-fired combined cycle (NGCC) plant. These three cases include
generating all required steam with an OTSG without carbon dioxide
capture, with partial capture of 32 percent of the carbon dioxide
produced by the OTSG for 40 percent carbon dioxide retention in the
reservoir, and with partial capture of 16 percent of the carbon
dioxide produced by the OTSG for 20 percent carbon dioxide
retention in the reservoir. Reservoir modeling shows that while
such fractions of the injected carbon dioxide may be retained in
the reservoir significant remaining amounts may return to the
surface in the produced gas making recycling possible.
[0028] For this analysis, an ideal carbon dioxide injection rate
selected corresponds to carbon dioxide at 11.4 percent of the steam
by mass. This carbon dioxide concentration results in lowering the
steam to oil ratio (SOR) from 2.5 to 2.125. Such reduction in the
SOR derives from benefits associated with injecting the carbon
dioxide with the steam, which benefits may include viscosity
reduction of the hydrocarbons from dissolution with the carbon
dioxide, insulating effects of the carbon dioxide or carbon dioxide
pressure support.
TABLE-US-00001 OTSG with Partial CO2 Capture 40 Percent CO2 20
Percent CO2 OTSG Retention Retention SOR 2.5 2.125 2.125 Steam
(tons per hour) Total 1488 1264 1264 CO2 Flowrates (tons per hour)
Captured 0 58 (32 percent) 29 (16 percent) Recycle 0 87 115 Total 0
144 144 Electrical Loads (megawatts) Facility base 92 92 92 CO2
recovery 0 2 1 CO2 compress 0 15 13 Total 92 109 106 Fuel Flowrates
(tons per hour) OTSG 78 68 66 NGCC 15 18 18 Total 93 86 84 Relative
usage 1 .92 .90 Green House Gas Emissions to Atmosphere (tons per
hour) CO2 emissions 251 173 196
[0029] Relative fuel usage shown in the table compares total fuel
used by being normalized to the steam only case without carbon
dioxide capture. The relative fuel use in the partial capture cases
range between 0.90-0.92, which represents reduction in fuel
operating expense relative to the steam only case using the OTSG
without any carbon dioxide capture. The partial capture application
also still enables recovering some of the carbon dioxide produced
such that carbon dioxide emissions may drop 22-31 percent in the
partial capture application relative to the steam only case without
any carbon dioxide capture.
[0030] The preferred embodiments of the invention have been
disclosed and illustrated. However, the invention is intended to be
as broad as defined in the claims below. Those skilled in the art
may be able to study the preferred embodiments and identify other
ways to practice the invention that are not exactly as described
herein. It is the intent of the inventors that variations and
equivalents of the invention are within the scope of the claims
below and the description, abstract and drawings are not to be used
to limit the scope of the invention.
* * * * *