CA2791318A1 - Steam flooding with oxygen injection, and cyclic steam stimulation with oxygen injection - Google Patents
Steam flooding with oxygen injection, and cyclic steam stimulation with oxygen injection Download PDFInfo
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- CA2791318A1 CA2791318A1 CA2791318A CA2791318A CA2791318A1 CA 2791318 A1 CA2791318 A1 CA 2791318A1 CA 2791318 A CA2791318 A CA 2791318A CA 2791318 A CA2791318 A CA 2791318A CA 2791318 A1 CA2791318 A1 CA 2791318A1
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- oxygen
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
- E21B43/24—Enhanced recovery methods for obtaining hydrocarbons using heat, e.g. steam injection
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
- E21B43/24—Enhanced recovery methods for obtaining hydrocarbons using heat, e.g. steam injection
- E21B43/243—Combustion in situ
Abstract
A process to recover heavy oil from a hydrocarbon reservoir, said process comprising injecting oxygen-containing gas and steam separately injected via separate wells into the reservoir to cause heated hydrocarbon fluids to flow more readily to a production well, wherein:
(i) the hydrocarbon is heavy oil (API from 10 to 20; with some initial gas injectivity (ii) the ratio of oxygen/steam injectant gas is controlled in the range from 0.05 to 1.00 (v/v) (iii) the process uses Cyclic Steam Stimulation or Steam Flooding techniques and well geometry, with extra well(s) or a segregated zone to inject oxygen gas wherein the oxygen contact zone within the reservoir is less than substantially 50 metres long.
(i) the hydrocarbon is heavy oil (API from 10 to 20; with some initial gas injectivity (ii) the ratio of oxygen/steam injectant gas is controlled in the range from 0.05 to 1.00 (v/v) (iii) the process uses Cyclic Steam Stimulation or Steam Flooding techniques and well geometry, with extra well(s) or a segregated zone to inject oxygen gas wherein the oxygen contact zone within the reservoir is less than substantially 50 metres long.
Description
TITLE OF THE INVENTION
Steam Flooding with Oxygen Injection, and Cyclic Steam Stimulation with Oxygen Injection FIELD OF THE INVENTION
The present invention relates to an enhanced oil recovery process for heavy oil in subterranean reservoirs and specifically processes for cyclic steam stimulation and/or steam flooding both improved by the additional step of injecting oxygen into the reservoir.
Acronym Dictionary of Terms API American Petroleum Institute (density) ASU Air Separation Unit (to produce oxygen gas) CAGD Combustion Assisted Gravity Drainage CIM Canadian Institute of Mining COFCAW Combination of Forward Combustion and Waterflood CSS Cyclic Steam Simulation CSSOX CSS with Oxygen DOE (US) Department of Energy EOR Enhanced Oil Recovery ETOR Energy to Oil Ratio (MMBTU/bbl) HTO High Temperature Oxidation ISC In Situ Combustion JCPT Journal of Canadian Petroleum Technology JPT Journal of Petroleum Technology LTO Low Temperature Oxidation OGJ Oil & Gas Journal 00IP Original Oil in Place
Steam Flooding with Oxygen Injection, and Cyclic Steam Stimulation with Oxygen Injection FIELD OF THE INVENTION
The present invention relates to an enhanced oil recovery process for heavy oil in subterranean reservoirs and specifically processes for cyclic steam stimulation and/or steam flooding both improved by the additional step of injecting oxygen into the reservoir.
Acronym Dictionary of Terms API American Petroleum Institute (density) ASU Air Separation Unit (to produce oxygen gas) CAGD Combustion Assisted Gravity Drainage CIM Canadian Institute of Mining COFCAW Combination of Forward Combustion and Waterflood CSS Cyclic Steam Simulation CSSOX CSS with Oxygen DOE (US) Department of Energy EOR Enhanced Oil Recovery ETOR Energy to Oil Ratio (MMBTU/bbl) HTO High Temperature Oxidation ISC In Situ Combustion JCPT Journal of Canadian Petroleum Technology JPT Journal of Petroleum Technology LTO Low Temperature Oxidation OGJ Oil & Gas Journal 00IP Original Oil in Place
2 SAGD Steam Assisted Gravity Drainage SAGDOX SAGD + Oxygen SF Steam Flood SFOX Steam Flood with Oxygen SOR Steam to Oil Ratio (bbls/bbl) SPE Society of Petroleum Engineers STARS Steam, Thermal and Advanced Process Reservoir Simulator References = Anderson, R.E. et al ¨ "Method of Direct Steam Generation Using an Oxyfuel Combustor", Int'l. Pat. W02010/101647 A2, 2010.
= Arabian Oil & Gas Company, "Middle East Enhanced Oil Recovery", May 5, 2011.
= Balog, S. et al., "The Wet Air Oxidation Boiler for EOR", JCP, Sept-Oct., 1982.
= Bousard, "Recovery of Oil by a Combustion of LTO and Hot Water or Steam Injection", U.S.Pat. 3976137, Aug., 1976.
= Butler, R.M., "Thermal Recovery of Oil & Bitumen", Prentice Hall, 1991.
= Carcoana, A.N., "Enhanced Oil Recovery in Rumania", SPE, Apr. 1982.
= Donaldson, E.G. et al, "Enhanced Oil Recovery II, Process and Operations Elsevier, 1989.
= Escobar, E., et al, "Optimization Methodology for Cyclic Steam Injection with Horizontal Wells", SPE/CIM, Nov., 2000.
= Farouq Ali, S.M., et al, ,"The Promise and Problems of Enhanced Oil Recovery Method. JCPT, July 1996.
= Frauenfeld, T.W.J. et al., "Effect of an Initial Gas Content on Thermal EOR
as Applied to Oil Sands", JPT, March, 1988.
= Green Car Congress, "Chevron leveraging information technology to optimize thermal production of heavy oil with increased recovery and reduced costs".
June 23,2011.
= Arabian Oil & Gas Company, "Middle East Enhanced Oil Recovery", May 5, 2011.
= Balog, S. et al., "The Wet Air Oxidation Boiler for EOR", JCP, Sept-Oct., 1982.
= Bousard, "Recovery of Oil by a Combustion of LTO and Hot Water or Steam Injection", U.S.Pat. 3976137, Aug., 1976.
= Butler, R.M., "Thermal Recovery of Oil & Bitumen", Prentice Hall, 1991.
= Carcoana, A.N., "Enhanced Oil Recovery in Rumania", SPE, Apr. 1982.
= Donaldson, E.G. et al, "Enhanced Oil Recovery II, Process and Operations Elsevier, 1989.
= Escobar, E., et al, "Optimization Methodology for Cyclic Steam Injection with Horizontal Wells", SPE/CIM, Nov., 2000.
= Farouq Ali, S.M., et al, ,"The Promise and Problems of Enhanced Oil Recovery Method. JCPT, July 1996.
= Frauenfeld, T.W.J. et al., "Effect of an Initial Gas Content on Thermal EOR
as Applied to Oil Sands", JPT, March, 1988.
= Green Car Congress, "Chevron leveraging information technology to optimize thermal production of heavy oil with increased recovery and reduced costs".
June 23,2011.
3 = Hanzlik, E.J., et at, "Forty Years of Steam Injection in California ¨ The Evolution of Heat Management", SPE, Oct., 2003.
= Heavyoilinfo.com, "Wafra pilot delivers for Chevron", Oct. 21, 2010.
= Hong, K.C., et at, "Effects of Noncondensable Gas Injection on Oil Recovery by Steam Floods, JPT, Dec. 1984.
= L. Lake et al, "A Niche for Enhanced Oil Recovery in the 1990's, Oilfield Rev., Jan. 1992.
= Leung, L.C., "Numerical Evaluation of the Effect of Simultaneous Steam and Carbon Dioxide Injection of the Recovery of Heavy Oil", JPT, Sept., 1983.
= Luo, R. et al, "Feasibility Study of CO2 Injection for Heavy Oil Reservoir After Cyclic Steam Simulation: Liaohe Oil Field Test", SPE, Nov. 2005.
= Kumar, M., et al, "Cyclic steaming in Heavy Oil Diatomite", SPE, March, 1995.
= Moore, R.G., et al, "In Situ Performance in Steam Flooded Heavy Oil Cores", JCP, Sept., 1999.
= Moore, R.G., et al, "Parametric Study of Steam Assisted In Situ Combustion", unpublished, Feb., 1994.
= Nasr, T.N., et at, "Thermal Techniques for the Recovery of Heavy Oil and Bitumen", SPE, Dec., 2005.
= OGJ, "More US EOR Projects start but EOR production continues to decline".
Apr 21, 2008.
= Parrish, D.R. et al, "Laboratory Study of a Combination of Forward Combustion and Waterflooding ¨ the COFCAW Process", JPT, June, 1969.
= Pfefferle, W.C., "Method for CAGD Recovery of Heavy Oil", Int'l Pat.
W02008/060311 A2, May, 2008.
= Praxair, website, 2010.
= Sarathi, P. "In Situ Combustion EOR Status", DOE, 1999.
= Sarkar et al, "Comparison of Thermal EOR Process Using Combinations of Vertical and Horizontal Wells", SPE, Feb., 1993.
= Stevens, S.H. et al, "A Versatile Model for Evaluation Thermal EOR
Economics"
SPE 1998.113, 1998.
= Heavyoilinfo.com, "Wafra pilot delivers for Chevron", Oct. 21, 2010.
= Hong, K.C., et at, "Effects of Noncondensable Gas Injection on Oil Recovery by Steam Floods, JPT, Dec. 1984.
= L. Lake et al, "A Niche for Enhanced Oil Recovery in the 1990's, Oilfield Rev., Jan. 1992.
= Leung, L.C., "Numerical Evaluation of the Effect of Simultaneous Steam and Carbon Dioxide Injection of the Recovery of Heavy Oil", JPT, Sept., 1983.
= Luo, R. et al, "Feasibility Study of CO2 Injection for Heavy Oil Reservoir After Cyclic Steam Simulation: Liaohe Oil Field Test", SPE, Nov. 2005.
= Kumar, M., et al, "Cyclic steaming in Heavy Oil Diatomite", SPE, March, 1995.
= Moore, R.G., et al, "In Situ Performance in Steam Flooded Heavy Oil Cores", JCP, Sept., 1999.
= Moore, R.G., et al, "Parametric Study of Steam Assisted In Situ Combustion", unpublished, Feb., 1994.
= Nasr, T.N., et at, "Thermal Techniques for the Recovery of Heavy Oil and Bitumen", SPE, Dec., 2005.
= OGJ, "More US EOR Projects start but EOR production continues to decline".
Apr 21, 2008.
= Parrish, D.R. et al, "Laboratory Study of a Combination of Forward Combustion and Waterflooding ¨ the COFCAW Process", JPT, June, 1969.
= Pfefferle, W.C., "Method for CAGD Recovery of Heavy Oil", Int'l Pat.
W02008/060311 A2, May, 2008.
= Praxair, website, 2010.
= Sarathi, P. "In Situ Combustion EOR Status", DOE, 1999.
= Sarkar et al, "Comparison of Thermal EOR Process Using Combinations of Vertical and Horizontal Wells", SPE, Feb., 1993.
= Stevens, S.H. et al, "A Versatile Model for Evaluation Thermal EOR
Economics"
SPE 1998.113, 1998.
4 = The Jakarta Post, "12 Oil Companies to use EOR methods to boost production", June 27,2011.
= Thomas, S. "Enhanced Oil Recovery ¨ An Overview", Oil & Gas Sci& Tech, 63, 2008.
= Wylie et al, "Hot Fluid Recovery of Heavy Oil with Steam and Carbon Dioxide", U.S. Pat. 2010/0276148 Al, Nov., 2010.
= Yang, X. et al, "Combustion Kinetics of Athabasca Bitumen from 1D Combustion Tube Experiments", Nat. Res. Res., 18, No.3, Sept. 2009(2).
= Yang, X. et al, "Design and Optimization of Hybrid Ex Situ/In Situ Steam Generation Recovery Process for Heavy Oil and Bitumen", SPE, Calgary, Oct.
2008.
= Yang, X. et al, "Design of Hybrid Steam - ISC Bitumen Recovery Processes".
Nat. Res. Res., Sept.3, 2009(1).
= Zawierucua et al., "Material Compatibility and Systems Considerations in Thermal EOR Environments containing High-Pressure oxygen, " JPT, Nov., 1988.
BACKGROUND OF THE INVENTION
Steam Floods (SF) and Cyclic Steam Stimulation (CSS) are EOR processes that recover heavy oil and/or bitumen. These processes have been practiced for over 50 years. The processes use steam to deliver heat energy to the reservoir. An alternative to steam is to use mixtures of steam and oxygen. Oxygen delivers heat by combustion to supplement steam energy delivery.
The present invention supplements and improves steam floods (SF) by adding oxygen gas (SFOX) and supplements and improves cyclic steam stimulation (CSS) by adding oxygen gas (CSSOX).
= Thomas, S. "Enhanced Oil Recovery ¨ An Overview", Oil & Gas Sci& Tech, 63, 2008.
= Wylie et al, "Hot Fluid Recovery of Heavy Oil with Steam and Carbon Dioxide", U.S. Pat. 2010/0276148 Al, Nov., 2010.
= Yang, X. et al, "Combustion Kinetics of Athabasca Bitumen from 1D Combustion Tube Experiments", Nat. Res. Res., 18, No.3, Sept. 2009(2).
= Yang, X. et al, "Design and Optimization of Hybrid Ex Situ/In Situ Steam Generation Recovery Process for Heavy Oil and Bitumen", SPE, Calgary, Oct.
2008.
= Yang, X. et al, "Design of Hybrid Steam - ISC Bitumen Recovery Processes".
Nat. Res. Res., Sept.3, 2009(1).
= Zawierucua et al., "Material Compatibility and Systems Considerations in Thermal EOR Environments containing High-Pressure oxygen, " JPT, Nov., 1988.
BACKGROUND OF THE INVENTION
Steam Floods (SF) and Cyclic Steam Stimulation (CSS) are EOR processes that recover heavy oil and/or bitumen. These processes have been practiced for over 50 years. The processes use steam to deliver heat energy to the reservoir. An alternative to steam is to use mixtures of steam and oxygen. Oxygen delivers heat by combustion to supplement steam energy delivery.
The present invention supplements and improves steam floods (SF) by adding oxygen gas (SFOX) and supplements and improves cyclic steam stimulation (CSS) by adding oxygen gas (CSSOX).
5 Review of Prior Art 2.1 Cyclic Steam Stimulation (CSS) Perhaps the oldest process for thermal FOR is cyclic steam stimulation (also called the "huff" and "puff' process).
As seen in Figure 3, the process takes place using a vertical well, in three steps¨first, steam is injected until injectivity/back-pressure limits injection rates or until a target slug size of steam is injected (the "huff" part of the cycle). For some reservoirs, fracture pressure may be exceeded during this phase to create fractures that aid in steam distribution and provide a conduit for oil flow. Second, the well is shut in and allowed to "soak" for a few weeks/months. This helps to spread heat by conduction and maximize the heated oil. Third, the well is put on production and oil flows to surface or is pumped to surface (the "puff' part of the cycle).
Although, a simple CSS process uses vertical wells, CSS can also be conducted using horizontal or deviated wells (Sarker (1993), Escobar (2000)). This can help distribute steam and shorten the flow path of heated heavy oil during the production phase.
CSS heats oil and reduces viscosity so the oil can more-easily flow to the production well. Steam also provides some gas drive during the production cycle. CSS also uses a form of gravity drainage, particularly if a partial steam chamber is retained around the vertical well during the soak phase (Figure 3). Oil can drain downward and replace steam as it condenses (Butler (1991)). The process has been labeled a "stimulation"
process, because even if the native oil has some mobility but rates are low, by heating oil and the matrix rock, steam can reduce near-well-bore resistance to oil flow and increase recovery rates.
CSS started in the 1950's in field trials. The largest CSS project in the world is now the Imperial Oil (EXXON) project at Cold Lake, Alberta (Table 4, Figure 5, Figure 8). For
As seen in Figure 3, the process takes place using a vertical well, in three steps¨first, steam is injected until injectivity/back-pressure limits injection rates or until a target slug size of steam is injected (the "huff" part of the cycle). For some reservoirs, fracture pressure may be exceeded during this phase to create fractures that aid in steam distribution and provide a conduit for oil flow. Second, the well is shut in and allowed to "soak" for a few weeks/months. This helps to spread heat by conduction and maximize the heated oil. Third, the well is put on production and oil flows to surface or is pumped to surface (the "puff' part of the cycle).
Although, a simple CSS process uses vertical wells, CSS can also be conducted using horizontal or deviated wells (Sarker (1993), Escobar (2000)). This can help distribute steam and shorten the flow path of heated heavy oil during the production phase.
CSS heats oil and reduces viscosity so the oil can more-easily flow to the production well. Steam also provides some gas drive during the production cycle. CSS also uses a form of gravity drainage, particularly if a partial steam chamber is retained around the vertical well during the soak phase (Figure 3). Oil can drain downward and replace steam as it condenses (Butler (1991)). The process has been labeled a "stimulation"
process, because even if the native oil has some mobility but rates are low, by heating oil and the matrix rock, steam can reduce near-well-bore resistance to oil flow and increase recovery rates.
CSS started in the 1950's in field trials. The largest CSS project in the world is now the Imperial Oil (EXXON) project at Cold Lake, Alberta (Table 4, Figure 5, Figure 8). For
6 this project, steam injection pressures cause vertical fractures to help distribute steam and provide enhanced flow channels for heated heavy oil. SAGD has now overtaken CSS as Canada's leading steam EOR process (Table 4). Soon SAGD will be the largest single project for steam FOR in Canada. But, CSS will remain a large producer.
CSS has also been recently introduced to the mid east (Arabian Oil & Gas (2011)). Some of the issues with CSS include the following:
(1) For heavy oils, recovery is limited to about 20% 00IP (Butler, (1992).
Another process may be necessary, post CSS, to exploit the reservoir (2) SOR deteriorates (increases) as the project matures.
(3) Production is not continuous, for isolated wells (4) Inter well communication may develop and necessitate cycle coordination of several wells and/or a change in recovery process.
(5) For bitumen, steam injectivity is too poor to run CSS
(6) High pressure CSS requires monitoring to prevent well bore damage
CSS has also been recently introduced to the mid east (Arabian Oil & Gas (2011)). Some of the issues with CSS include the following:
(1) For heavy oils, recovery is limited to about 20% 00IP (Butler, (1992).
Another process may be necessary, post CSS, to exploit the reservoir (2) SOR deteriorates (increases) as the project matures.
(3) Production is not continuous, for isolated wells (4) Inter well communication may develop and necessitate cycle coordination of several wells and/or a change in recovery process.
(5) For bitumen, steam injectivity is too poor to run CSS
(6) High pressure CSS requires monitoring to prevent well bore damage
(7) Steam override 2.2 Steam Floods (SF) If injectivity is good or if CSS wells start communicating, the process can be changed to a steam flood, where steam is injected continuously into one (or more) well and "pushes"
heated oil to one (or more) production wells. Figure 9 shows the simple SF
geometry using vertical wells. Usually the wells are arranged in regular patterns (e.g.
Figure 12).
SF processes can recover more oil than CSS, but, one of the problems with SF
processes is steam override, where steam rises to the top of the pay zone and breaks through to the production well, bypassing the heated oil bank. This can reduce productivity or even cause a premature abandonment of the process. If the reservoir dips, it is advantageous to arrange the wells so the steam injector is higher than the producer to take advantage of gravity drainage and to minimize steam override (e.g. California heavy oils).
One of the recent trends in SF is to consider the process, at least partially, as a gravity drainage process and manage heat input and production like SAGD (Green Car Cong.
(2011). If this is done, recovery factors can approach 70-80%, similar to SAGD
(ibid).
Horizontal wells are also being considered to improve productivity and recovery (Green Car Cong. (2011)). SAGD (Figure 2) can be considered as a vertical SF using gravity drainage as the dominant recovery mechanism (Butler, (1991)). Tangleflags, Sask. is an example of a vertical SF using a combination of vertical steam injectors and horizontal production wells (Figure 7, Thomas (2008)). SF based solely on horizontal wells is also feasible (Figure 10).
Screening criteria for CSS and SF are similar (Table 2), but SF processes can recover more oil than CSS and SF has dominated world production for thermal FOR
(Figure 1).
Both CSS and SF have limitations in oil density (API>10), oil viscosity (p. <
1000 cp.), depth (<5000 ft.), pay thickness (>20 ft.) and initial oil saturation (S0>
.50). But, many of these limitations are economic and were evaluated in an economic environment with low oil prices (<$30/bbl), so the screens may be outdated. They are not hard technical barriers. Figure 6 shows thermal (steam) EOR is a medium-cost FOR process (Lake (1992)).
SF FOR began in the USA in the 1950-1960's (Lake (1992)) and the USA has continued as a dominant player (Figure 5). In 1998, California SF projects produced about 400 KBD using 20,000 vertical wells in the Bakersfield area (Stevens (1998)).
Chevron is the largest US producer (Green, (2011)). The largest single SF project is the Dun i field, operated by Caltex, in Indonesia, currently producing about 300 KBD (Jakarta Post (2011), Figure 8). SF technology has also been introduced to the Mid East (heavyoilinfo (2010), Arabian Oil & Gas (2011)).
Some of the problems with SF include the following:
(1) SOR can be poor (higher than for SAGD).
heated oil to one (or more) production wells. Figure 9 shows the simple SF
geometry using vertical wells. Usually the wells are arranged in regular patterns (e.g.
Figure 12).
SF processes can recover more oil than CSS, but, one of the problems with SF
processes is steam override, where steam rises to the top of the pay zone and breaks through to the production well, bypassing the heated oil bank. This can reduce productivity or even cause a premature abandonment of the process. If the reservoir dips, it is advantageous to arrange the wells so the steam injector is higher than the producer to take advantage of gravity drainage and to minimize steam override (e.g. California heavy oils).
One of the recent trends in SF is to consider the process, at least partially, as a gravity drainage process and manage heat input and production like SAGD (Green Car Cong.
(2011). If this is done, recovery factors can approach 70-80%, similar to SAGD
(ibid).
Horizontal wells are also being considered to improve productivity and recovery (Green Car Cong. (2011)). SAGD (Figure 2) can be considered as a vertical SF using gravity drainage as the dominant recovery mechanism (Butler, (1991)). Tangleflags, Sask. is an example of a vertical SF using a combination of vertical steam injectors and horizontal production wells (Figure 7, Thomas (2008)). SF based solely on horizontal wells is also feasible (Figure 10).
Screening criteria for CSS and SF are similar (Table 2), but SF processes can recover more oil than CSS and SF has dominated world production for thermal FOR
(Figure 1).
Both CSS and SF have limitations in oil density (API>10), oil viscosity (p. <
1000 cp.), depth (<5000 ft.), pay thickness (>20 ft.) and initial oil saturation (S0>
.50). But, many of these limitations are economic and were evaluated in an economic environment with low oil prices (<$30/bbl), so the screens may be outdated. They are not hard technical barriers. Figure 6 shows thermal (steam) EOR is a medium-cost FOR process (Lake (1992)).
SF FOR began in the USA in the 1950-1960's (Lake (1992)) and the USA has continued as a dominant player (Figure 5). In 1998, California SF projects produced about 400 KBD using 20,000 vertical wells in the Bakersfield area (Stevens (1998)).
Chevron is the largest US producer (Green, (2011)). The largest single SF project is the Dun i field, operated by Caltex, in Indonesia, currently producing about 300 KBD (Jakarta Post (2011), Figure 8). SF technology has also been introduced to the Mid East (heavyoilinfo (2010), Arabian Oil & Gas (2011)).
Some of the problems with SF include the following:
(1) SOR can be poor (higher than for SAGD).
8 (2) Start-up may be difficult or prolonged because of injectivity limitations or lack of communication between injectors and producers. Often, SF is started by CSS.
(3) Fracturing can also be an issue. If a fracture is formed, steam will flow in the fracture and transfer heat, by conduction, to surrounding oil. But, production will be slow because the steam is not driving the oil to the production well.
(4) If the reservoir is too deep, heat losses are a concern.
(5) Steam override is always an issue, unless we have a tilted reservoir with a gravity drive component.
(6) Ultimate recovery, without gravity drainage, can still be poor (30 to 40%
00IP).
2.3 Steam + Oxygen COFCAW (combination of forward combustion and waterflood) is a version of an ISC
process that injects water to produce steam in the reservoir. It produces a steam + oxygen (or air) mixture, upstream of the combustion front (Parrish (1969)). But, the process is a modified 1SC process, not a modified SF process, and it is suited to a vertical well geometry, not to a horizontal well geometry. If liquid water is allowed to impinge on the combustion front, HTO will be quenched and either oxygen gas will break through to the production well or LTO oxidation will occur. LTO is undesirable because oxygen use is incomplete, heat release per unit oxygen consumed is less than HTO, and oxidation products include organic acids that can create undesirable emulsions that can cause reservoir blockages and/or oil/water (treating) separation problems.
When oxygen combusts in a hydrocarbon reservoir, the dominant, non-condensable gas produced is carbon dioxide. Steam + 02 injected will produce steam + CO2 in the reservoir. Several studies have looked at steam + CO2 for CSS or SF EOR
applications (Luo (2005), Frauenfeld (1988), Balog (1982)). There has also been some activity to produce steam + CO2 or steam + flue gas mixtures using surface or down hole equipment (Balog (1982), Wylie (2010), Anderson (2010)). Steam + CO2 generally has been shown to improve steam-only processes (CSS or SF). The incremental benefits of CO2 may be
(3) Fracturing can also be an issue. If a fracture is formed, steam will flow in the fracture and transfer heat, by conduction, to surrounding oil. But, production will be slow because the steam is not driving the oil to the production well.
(4) If the reservoir is too deep, heat losses are a concern.
(5) Steam override is always an issue, unless we have a tilted reservoir with a gravity drive component.
(6) Ultimate recovery, without gravity drainage, can still be poor (30 to 40%
00IP).
2.3 Steam + Oxygen COFCAW (combination of forward combustion and waterflood) is a version of an ISC
process that injects water to produce steam in the reservoir. It produces a steam + oxygen (or air) mixture, upstream of the combustion front (Parrish (1969)). But, the process is a modified 1SC process, not a modified SF process, and it is suited to a vertical well geometry, not to a horizontal well geometry. If liquid water is allowed to impinge on the combustion front, HTO will be quenched and either oxygen gas will break through to the production well or LTO oxidation will occur. LTO is undesirable because oxygen use is incomplete, heat release per unit oxygen consumed is less than HTO, and oxidation products include organic acids that can create undesirable emulsions that can cause reservoir blockages and/or oil/water (treating) separation problems.
When oxygen combusts in a hydrocarbon reservoir, the dominant, non-condensable gas produced is carbon dioxide. Steam + 02 injected will produce steam + CO2 in the reservoir. Several studies have looked at steam + CO2 for CSS or SF EOR
applications (Luo (2005), Frauenfeld (1988), Balog (1982)). There has also been some activity to produce steam + CO2 or steam + flue gas mixtures using surface or down hole equipment (Balog (1982), Wylie (2010), Anderson (2010)). Steam + CO2 generally has been shown to improve steam-only processes (CSS or SF). The incremental benefits of CO2 may be
9 reduced if the heavy oil already contains some dissolved gas (Frauenfeld (1988)). In some cases the improvement due to CO2 was manifest in oil production rates, not in ultimate recovery (Leung, (1983)).
Activity based on steam + oxygen injection has been much less than steam +
CO2.
Laboratory combustion tube tests have been performed using mixtures of steam +
oxygen (Moore (1994), (1999)). Combustion was very robust, showing good HTO
combustion, even for very low oxygen concentrations in the mixture. The combustion was stable and more complete (less CO) than other oxidants (steam + air; air). Oxygen concentrations in the mix varied from under 3 to over 12% (v/v).
Yang (2008) (2009(1)) proposed to use steam + oxygen as an alternative to steam in a SAGD process. The process was simulated using a modified STARS simulation model, incorporating combustion kinetics. Yang demonstrated that for all oxygen mixes, the combustion zone was contained in the gas/steam chamber, using residual bitumen as a fuel. The combustion front never intersected the steam chamber walls. But, the steam/gas chamber was contained with no provision to remove non-condensable gases. So, back pressure in the gas chamber inhibited gas injection and bitumen production, using steam + oxygen mixtures. Also, there was no consideration of the corrosion issue for steam +
oxygen injection in a horizontal well, nor was there any consideration of minimum oxygen flux rates to initiate and sustain HTO combustion using a long horizontal well for 02 injection.
Yang ((2008), 2009(1)) also proposed an alternating steam/oxygen process as an alternative to continuous injection of steam + 02 mixes. But, issues of corrosion, minimum oxygen flux maintenance, ignition risks and combustion stability maintenance, were not addressed.
Bousard (1976) proposed to inject air or oxygen with hot water or steam to propagate LTO combustion as a method to inject heat into a heavy oil reservoir. But HTO
is desirable and LTO is undesirable, as discussed above.
Activity based on steam + oxygen injection has been much less than steam +
CO2.
Laboratory combustion tube tests have been performed using mixtures of steam +
oxygen (Moore (1994), (1999)). Combustion was very robust, showing good HTO
combustion, even for very low oxygen concentrations in the mixture. The combustion was stable and more complete (less CO) than other oxidants (steam + air; air). Oxygen concentrations in the mix varied from under 3 to over 12% (v/v).
Yang (2008) (2009(1)) proposed to use steam + oxygen as an alternative to steam in a SAGD process. The process was simulated using a modified STARS simulation model, incorporating combustion kinetics. Yang demonstrated that for all oxygen mixes, the combustion zone was contained in the gas/steam chamber, using residual bitumen as a fuel. The combustion front never intersected the steam chamber walls. But, the steam/gas chamber was contained with no provision to remove non-condensable gases. So, back pressure in the gas chamber inhibited gas injection and bitumen production, using steam + oxygen mixtures. Also, there was no consideration of the corrosion issue for steam +
oxygen injection in a horizontal well, nor was there any consideration of minimum oxygen flux rates to initiate and sustain HTO combustion using a long horizontal well for 02 injection.
Yang ((2008), 2009(1)) also proposed an alternating steam/oxygen process as an alternative to continuous injection of steam + 02 mixes. But, issues of corrosion, minimum oxygen flux maintenance, ignition risks and combustion stability maintenance, were not addressed.
Bousard (1976) proposed to inject air or oxygen with hot water or steam to propagate LTO combustion as a method to inject heat into a heavy oil reservoir. But HTO
is desirable and LTO is undesirable, as discussed above.
10 Pfefferle (2008) suggested using oxygen + steam mixtures in a SAGD process, as a way to reduce steam demands and to partially upgrade heavy oil. Combustion was purported to occur at the bitumen interface (the chamber wall) and combustion temperature was controlled by adjusting oxygen concentrations. But, as shown by Yang, combustion will not occur at the chamber walls. It will occur inside the steam chamber, using residual bitumen as a fuel not bitumen from/at the chamber wall. Also, combustion temperature is almost independent of oxygen concentration (Butler, 1991). It is dependant on fuel (coke) lay-down rates by the combustion/pyrolysis process. Pfefferle also suggested oxygen injection over the full length of a horizontal well and did not address the issues of corrosion, nor of maintaining minimum oxygen flux rates if a long horizontal well is used for injection.
It is therefore a primary object of the invention to provide an enhanced oil recovery process for both steam flooding and cyclic steam stimulation wherein oxygen and steam are injected separately into a heavy oil reservoir.
It is a further object of the invention to provide at least one well to vent produced gases from the reservoir to control reservoir pressures.
It is yet a further object of the invention to provide oxygen at an amount of substantially 35% (v/v) and corresponding steam levels at 65%.
It is yet a further object of the invention to provide pipe sizes for CSSOX or SFOX wells that may be much smaller than for steam-only processes because oxygen carries about ten times the heat content, per unit volume.
Further and other objects of the invention will be apparent to one skilled in the art when considering the following summary of the invention and the more detailed description of the preferred embodiments illustrated herein.
It is therefore a primary object of the invention to provide an enhanced oil recovery process for both steam flooding and cyclic steam stimulation wherein oxygen and steam are injected separately into a heavy oil reservoir.
It is a further object of the invention to provide at least one well to vent produced gases from the reservoir to control reservoir pressures.
It is yet a further object of the invention to provide oxygen at an amount of substantially 35% (v/v) and corresponding steam levels at 65%.
It is yet a further object of the invention to provide pipe sizes for CSSOX or SFOX wells that may be much smaller than for steam-only processes because oxygen carries about ten times the heat content, per unit volume.
Further and other objects of the invention will be apparent to one skilled in the art when considering the following summary of the invention and the more detailed description of the preferred embodiments illustrated herein.
11 SUMMARY OF INVENTION
According to a primary aspect of the invention there is provided a process to recover heavy oil from a hydrocarbon reservoir, said process comprising injecting oxygen-containing gas and steam separately injected via separate wells into the reservoir to cause heated hydrocarbon fluids to flow more readily to a production well, wherein:
(i) the hydrocarbon is heavy oil (API from 10 to 20; with some initial gas inj ectivity) (ii) the ratio of oxygen/steam injectant gas is controlled in the range from 0.05 to 1.00 (v/v) (iii) the process uses Cyclic Steam Stimulation or Steam Flooding techniques and well geometry, with extra well(s) or a segregated zone to inject oxygen gas, wherein the oxygen contact zone within the reservoir is less than substantially 50 metres long.
Preferably a separate well or segregation is used for non-condensable gas produced by combustion.
In one embodiment the oxygen-containing gas has an oxygen content of 95 to 99.9%
(v/v).and preferably wherein the oxygen-containing gas has an oxygen content of 95 to 97% (v/v), In another embodiment the oxygen-containing gas is air.
Preferably the oxygen-containing gas is enriched air with an oxygen content of substantially 20 to 95% (v/v).
In one embodiment the oxygen injection well within the reservoir is less than substantially 50 metres long proximate a steam swept zone.
According to a primary aspect of the invention there is provided a process to recover heavy oil from a hydrocarbon reservoir, said process comprising injecting oxygen-containing gas and steam separately injected via separate wells into the reservoir to cause heated hydrocarbon fluids to flow more readily to a production well, wherein:
(i) the hydrocarbon is heavy oil (API from 10 to 20; with some initial gas inj ectivity) (ii) the ratio of oxygen/steam injectant gas is controlled in the range from 0.05 to 1.00 (v/v) (iii) the process uses Cyclic Steam Stimulation or Steam Flooding techniques and well geometry, with extra well(s) or a segregated zone to inject oxygen gas, wherein the oxygen contact zone within the reservoir is less than substantially 50 metres long.
Preferably a separate well or segregation is used for non-condensable gas produced by combustion.
In one embodiment the oxygen-containing gas has an oxygen content of 95 to 99.9%
(v/v).and preferably wherein the oxygen-containing gas has an oxygen content of 95 to 97% (v/v), In another embodiment the oxygen-containing gas is air.
Preferably the oxygen-containing gas is enriched air with an oxygen content of substantially 20 to 95% (v/v).
In one embodiment the oxygen injection well within the reservoir is less than substantially 50 metres long proximate a steam swept zone.
12 Preferably the oxygen-containing gas injection step is started only after a steam-swept zone is formed around the injection point, preferably controlled by:
(i) adjusting steam and oxygen flow ratios to attain a target.
(ii) adjusting steam + oxygen flows to attain an energy rate target.
In a preferred embodiment a separate produced gas removal well is used to minimize steam override to production wells.
Preferably oxygen/steam (v/v) ratios start at about 0.05 and ramp up to 1.00 as the process matures.
In another embodiment the oxygen/steam (v/v) ratio is held between 0.4 and 0.7 and most preferably 0.35.
In a further embodiment the ratio of oxygen/steam (v/v) is between 0.4 and 0.7 and the oxygen purity in the oxygen-containing gas is between 95 and 97% (v/v).
In another embodiment the process further comprises an injector well (either a separate vertical well or the segregated portion of a well) having a maximum perforated zone (or zone with slotted liners) of less than substantially 50 m so that oxygen flux rates can be maximized.
Preferably Oxygen is injected proximate a steam-swept zone, whereby combustion of residual fuel in the reservoir is the source of energy for said combustion, said zone being preheated, at start-up, so spontaneous High Temperature Oxidation can occur.
According to yet another embodiment of the invention there is provided an improved Cyclic Steam Stimulation Enhanced Oil Recovery process to recover heavy oil comprising adding oxygen gas during a typical steam-injection cycle (the "huff), the
(i) adjusting steam and oxygen flow ratios to attain a target.
(ii) adjusting steam + oxygen flows to attain an energy rate target.
In a preferred embodiment a separate produced gas removal well is used to minimize steam override to production wells.
Preferably oxygen/steam (v/v) ratios start at about 0.05 and ramp up to 1.00 as the process matures.
In another embodiment the oxygen/steam (v/v) ratio is held between 0.4 and 0.7 and most preferably 0.35.
In a further embodiment the ratio of oxygen/steam (v/v) is between 0.4 and 0.7 and the oxygen purity in the oxygen-containing gas is between 95 and 97% (v/v).
In another embodiment the process further comprises an injector well (either a separate vertical well or the segregated portion of a well) having a maximum perforated zone (or zone with slotted liners) of less than substantially 50 m so that oxygen flux rates can be maximized.
Preferably Oxygen is injected proximate a steam-swept zone, whereby combustion of residual fuel in the reservoir is the source of energy for said combustion, said zone being preheated, at start-up, so spontaneous High Temperature Oxidation can occur.
According to yet another embodiment of the invention there is provided an improved Cyclic Steam Stimulation Enhanced Oil Recovery process to recover heavy oil comprising adding oxygen gas during a typical steam-injection cycle (the "huff), the
13 "soak" and "puff' cycles being similar to conventional CSS, wherein the injection of Oxygen provides extra energy from combustion of residual oil , for heavy oil recovery while creating CO2 in the reservoir and removing produced CO2 separately to better control the process.
Preferably an extra oxygen injection well is utilized.
Preferably the process further comprises segregating oxygen injection within steam injection wells using separate tubing and a packer.
Steam and oxygen are injected at separate times, as long as oxygen injection follows steam, so the reservoir is preheated for auto-ignition of High Temperature Oxidation combustion.
In one embodiment of the process oxygen injection is segregated near the top of the injector well or using a separate 02 well, during the "huff' cycle, by injecting steam and oxygen; and during the "puff" cycle removing produced gases (mainly CO2) separately to better control the process.
In a preferred embodiment the CSSOX process is the startup process for a SFOX
process.
According to yet another aspect of the invention there is provided an improved Steam Flooding (SFOX EOR) process Enhanced Oil Recovery to recover heavy oil, basically similar to a conventional SF process, the improvement comprising injection of oxygen gas continuously injected near (or at) the steam injector to provide an added source of energy from in situ combustion of residual fuels, said Steam and oxygen being injected in a vertical-well geometry, with producer/injector wells arranged in regular patterns.
In a preferred embodiment separate wells are provided to remove non-condensable combustion gases.
Preferably an extra oxygen injection well is utilized.
Preferably the process further comprises segregating oxygen injection within steam injection wells using separate tubing and a packer.
Steam and oxygen are injected at separate times, as long as oxygen injection follows steam, so the reservoir is preheated for auto-ignition of High Temperature Oxidation combustion.
In one embodiment of the process oxygen injection is segregated near the top of the injector well or using a separate 02 well, during the "huff' cycle, by injecting steam and oxygen; and during the "puff" cycle removing produced gases (mainly CO2) separately to better control the process.
In a preferred embodiment the CSSOX process is the startup process for a SFOX
process.
According to yet another aspect of the invention there is provided an improved Steam Flooding (SFOX EOR) process Enhanced Oil Recovery to recover heavy oil, basically similar to a conventional SF process, the improvement comprising injection of oxygen gas continuously injected near (or at) the steam injector to provide an added source of energy from in situ combustion of residual fuels, said Steam and oxygen being injected in a vertical-well geometry, with producer/injector wells arranged in regular patterns.
In a preferred embodiment separate wells are provided to remove non-condensable combustion gases.
14 Preferably the process further comprises use of horizontal wells, especially for the more viscous heavy oils.
In a preferred embodiment of the process the pipe sizes for CSSOX or SFOX
wells can be much smaller than for steam-only processes because oxygen carries about ten times the heat content, per unit volume.
BRIEF DESCRIPTION OF THE FIGURES
Figure 1 illustrates World EOR Production.
Figure 2 illustrates the SAGD EOR Process.
Figure 3 illustrates the CSS Process.
Figure 4 illustrates an oil viscosity chart.
Figure 5 illustrates USA/Canada Steam EOR.
Figure 6 illustrates a cost comparison of EOR methods.
Figure 7 illustrates Tangleflags steam flood.
Figure 8 charts the Kern River, California and Dun, Indonesia SF projects.
Figure 9 illustrates SF geometry.
Figure 10 illustrates a horizontal well SF.
Figure 11 illustrates a SFOX geometry.
In a preferred embodiment of the process the pipe sizes for CSSOX or SFOX
wells can be much smaller than for steam-only processes because oxygen carries about ten times the heat content, per unit volume.
BRIEF DESCRIPTION OF THE FIGURES
Figure 1 illustrates World EOR Production.
Figure 2 illustrates the SAGD EOR Process.
Figure 3 illustrates the CSS Process.
Figure 4 illustrates an oil viscosity chart.
Figure 5 illustrates USA/Canada Steam EOR.
Figure 6 illustrates a cost comparison of EOR methods.
Figure 7 illustrates Tangleflags steam flood.
Figure 8 charts the Kern River, California and Dun, Indonesia SF projects.
Figure 9 illustrates SF geometry.
Figure 10 illustrates a horizontal well SF.
Figure 11 illustrates a SFOX geometry.
15 Figure 12 illustrates a 5-spot pattern for SFOX.
Figure 13 illustrates well geometry for CSSOX 1.
Figure 14 illustrates well geometry for CSSOX 2.
Figure 15 illustrates residual bitumen in steam-swept zones.
Figure 16 illustrates SFOX geometry.
Figure 17 illustrates another SFOX geometry.
Figure 18 illustrates CSSOX with produced gas removal.
DETAILED DESCRIPTION OF THE INVENTION
3.1 Steam + Oxygen If we inject steam and oxygen, in separate or segregated streams, into a heavy oil reservoir, we have two separate sources of heat. Oxygen will cause combustion of the residual heavy oil left behind by steam. As shown in Figure 15, we can expect residual heavy oil to be about 10% (v/v) (of pore space). This is sufficient to support and sustain combustion. Steam can transfer heat directly to the reservoir constituents from latent heat (heat released when steam condenses) or from sensible heat (heat transferred as hot condensate cools).
As previously discussed (2.3), there are two kinds of oxidation that can occur HTO (380-800 C) where combustion produces mostly CO,, CO and H20 and LTO (150-300 C) where combustion produces partially oxidized compounds including organic acids that can cause production difficulties. HTO is desirable and LTO is undesirable.
Figure 13 illustrates well geometry for CSSOX 1.
Figure 14 illustrates well geometry for CSSOX 2.
Figure 15 illustrates residual bitumen in steam-swept zones.
Figure 16 illustrates SFOX geometry.
Figure 17 illustrates another SFOX geometry.
Figure 18 illustrates CSSOX with produced gas removal.
DETAILED DESCRIPTION OF THE INVENTION
3.1 Steam + Oxygen If we inject steam and oxygen, in separate or segregated streams, into a heavy oil reservoir, we have two separate sources of heat. Oxygen will cause combustion of the residual heavy oil left behind by steam. As shown in Figure 15, we can expect residual heavy oil to be about 10% (v/v) (of pore space). This is sufficient to support and sustain combustion. Steam can transfer heat directly to the reservoir constituents from latent heat (heat released when steam condenses) or from sensible heat (heat transferred as hot condensate cools).
As previously discussed (2.3), there are two kinds of oxidation that can occur HTO (380-800 C) where combustion produces mostly CO,, CO and H20 and LTO (150-300 C) where combustion produces partially oxidized compounds including organic acids that can cause production difficulties. HTO is desirable and LTO is undesirable.
16 A convenient way to label steam + oxygen processes, for CSS or SF
applications, is to consider the oxygen content in the steam + oxygen mix. (This doesn't imply that we inject a mixture or that we expect good mixing in the reservoir). Using this terminology, CSSOX (10) implies a 10% (v/v) oxygen concentration in a steam/oxygen mix used for a CSS application (CSSOX=CSS with oxygen). SFOX (10) implies the same mix used for an SF application.
Table 1 shows the properties of various steam + oxygen mixes, where we assume the heat release for oxygen combustion is 480 BTU/SCF (Butler (1991)) and we use an average steam heat content of 1000 BTU/lb. Because oxygen contains about 10 times the heat content of a similar volume of steam, as oxygen concentration in the mix increases, oxygen quickly dominates heat delivery. The transition point where oxygen heat = steam heat is for a mixture containing 9% (v/v) oxygen.
Mixtures of saturated steam and oxygen are very corrosive to carbon steel and other alloys (Zawierucha (1988)). Separate wells or a segregation system are needed.
One suggestion (Yang (2009)) is to use a steam injector for alternating volumes of steam and oxygen. But, to sustain HTO combustion, we need a constant supply and a minimum flux of oxygen (Sarathi (1999)), otherwise oxygen will break through to production wells or LTO combustion may start.
It has also been suggested that we can simply inject mixtures of steam +
oxygen and control corrosion using appropriate alloys or inhibitors (Yang (2009), Pfefferle (2008)) but this is difficult (Zawierucha (1988)). If a horizontal well is used as an injector, we have corrosion issues, and oxygen flux rates may be a concern. Oxygen flux is diluted over the length of the horizontal well. In some areas, oxygen flux may be too low to sustain HTO. Even if average flux rates are satisfactory, inhomogeneties in the reservoir may cause local oxygen depletions.
applications, is to consider the oxygen content in the steam + oxygen mix. (This doesn't imply that we inject a mixture or that we expect good mixing in the reservoir). Using this terminology, CSSOX (10) implies a 10% (v/v) oxygen concentration in a steam/oxygen mix used for a CSS application (CSSOX=CSS with oxygen). SFOX (10) implies the same mix used for an SF application.
Table 1 shows the properties of various steam + oxygen mixes, where we assume the heat release for oxygen combustion is 480 BTU/SCF (Butler (1991)) and we use an average steam heat content of 1000 BTU/lb. Because oxygen contains about 10 times the heat content of a similar volume of steam, as oxygen concentration in the mix increases, oxygen quickly dominates heat delivery. The transition point where oxygen heat = steam heat is for a mixture containing 9% (v/v) oxygen.
Mixtures of saturated steam and oxygen are very corrosive to carbon steel and other alloys (Zawierucha (1988)). Separate wells or a segregation system are needed.
One suggestion (Yang (2009)) is to use a steam injector for alternating volumes of steam and oxygen. But, to sustain HTO combustion, we need a constant supply and a minimum flux of oxygen (Sarathi (1999)), otherwise oxygen will break through to production wells or LTO combustion may start.
It has also been suggested that we can simply inject mixtures of steam +
oxygen and control corrosion using appropriate alloys or inhibitors (Yang (2009), Pfefferle (2008)) but this is difficult (Zawierucha (1988)). If a horizontal well is used as an injector, we have corrosion issues, and oxygen flux rates may be a concern. Oxygen flux is diluted over the length of the horizontal well. In some areas, oxygen flux may be too low to sustain HTO. Even if average flux rates are satisfactory, inhomogeneties in the reservoir may cause local oxygen depletions.
17 Oxygen needs to be injected into (or near to) a steam-swept zone, so combustion of residual fuel is the source of energy and injectivity is not a problem. The zone needs to be preheated, at start-up, so spontaneous HTO occurs.
There is a synergy between steam and oxygen for in situ EOR processes. Steam helps combustion by preheating the reservoir so auto-ignition can occur. In the combustion zone, steam adds OH and H radicals that improve (accelerate) and stabilize HTO
combustion (analogous to smokeless flare technology). Steam is an effective heat transfer medium to attain high productivity. Steam also increases combustion completeness (Moore (1994)). Oxygen helps steam by reducing steam/water demands per unit energy injected, generating extra steam by reflux, vaporizing connate water and producing steam directly as a product of combustion. Oxygen also increases energy efficiency.
Oxygen adds CO2 that can dissolve into heavy oil to reduce viscosity; providing dissolved gas drive recovery mechanisms. When non-condensable gases migrate to the top of the pay zone they will partially insulate the process from heat loss to the overburden, extending the economic limit (oxygen costs less than steam per unit heat delivered to the reservoir) to increase ultimate recovery. Lastly, if some CO2 is retained in the reservoir, CO2 emissions can be reduced.
3.2 In Situ Combustipn Chemistry Oxygen creates energy in a heavy oil reservoir by combustion. The 'coke" that is prepared by hot combustion gases fractionating and polymerizing residual heavy oil, can be represented by a reduced formula of CH5. This ignores trace components (S, N, 0,...
etc) and it doesn't imply a molecular structure nor a molecular size. It only means that the "coke" has an WC atomic ratio of 0.5.
Let's also assume:
(1) CO in the product gases is about 10% of the carbon combusted (see Moore (1994)) for HTO.
There is a synergy between steam and oxygen for in situ EOR processes. Steam helps combustion by preheating the reservoir so auto-ignition can occur. In the combustion zone, steam adds OH and H radicals that improve (accelerate) and stabilize HTO
combustion (analogous to smokeless flare technology). Steam is an effective heat transfer medium to attain high productivity. Steam also increases combustion completeness (Moore (1994)). Oxygen helps steam by reducing steam/water demands per unit energy injected, generating extra steam by reflux, vaporizing connate water and producing steam directly as a product of combustion. Oxygen also increases energy efficiency.
Oxygen adds CO2 that can dissolve into heavy oil to reduce viscosity; providing dissolved gas drive recovery mechanisms. When non-condensable gases migrate to the top of the pay zone they will partially insulate the process from heat loss to the overburden, extending the economic limit (oxygen costs less than steam per unit heat delivered to the reservoir) to increase ultimate recovery. Lastly, if some CO2 is retained in the reservoir, CO2 emissions can be reduced.
3.2 In Situ Combustipn Chemistry Oxygen creates energy in a heavy oil reservoir by combustion. The 'coke" that is prepared by hot combustion gases fractionating and polymerizing residual heavy oil, can be represented by a reduced formula of CH5. This ignores trace components (S, N, 0,...
etc) and it doesn't imply a molecular structure nor a molecular size. It only means that the "coke" has an WC atomic ratio of 0.5.
Let's also assume:
(1) CO in the product gases is about 10% of the carbon combusted (see Moore (1994)) for HTO.
18 (2) Water-gas-shift reactions occur to completion in the reservoir¨i.e. CO +
4 CO2 + H2 + HEAT. This reaction is favored by lower T (lower than combustion) and by high concentrations of steam. The heat release is small compared to combustion.
Then, our net combustion stoichiometry is determined as follows:
Combustion: CH5 -I 1.075024 0.9CO2 + 0.1C0 + 0.25H20 + HEAT
Shift: 0.1C0 + 0.11-1,0 4 0.1CO, + 0.1142 + HEAT
Net: CH5 + 1.075024 CO/ + 0.11-12 + 0.15H20 + HEAT
Features are as follows:
(1) heat release = 480 BTU/SCF 02 (Butler (1991)) (2) non-condensable gas make = 102% of oxygen used (v/v) (3) combustion net water make = 14% of oxygen used (v/v) (4) hydrogen gas make = 9.3% of oxygen used (v/v) (5) produced gas composition ((v/v) %):
Wet Dry CO2 80.0 90.9 8.0 9.1 1120 12.0 Total 100.0 100.0 (6) Combustion temperature is controlled by "coke" content and matrix properties.
Typically, HTO combustion T is between (380-800 C).
4 CO2 + H2 + HEAT. This reaction is favored by lower T (lower than combustion) and by high concentrations of steam. The heat release is small compared to combustion.
Then, our net combustion stoichiometry is determined as follows:
Combustion: CH5 -I 1.075024 0.9CO2 + 0.1C0 + 0.25H20 + HEAT
Shift: 0.1C0 + 0.11-1,0 4 0.1CO, + 0.1142 + HEAT
Net: CH5 + 1.075024 CO/ + 0.11-12 + 0.15H20 + HEAT
Features are as follows:
(1) heat release = 480 BTU/SCF 02 (Butler (1991)) (2) non-condensable gas make = 102% of oxygen used (v/v) (3) combustion net water make = 14% of oxygen used (v/v) (4) hydrogen gas make = 9.3% of oxygen used (v/v) (5) produced gas composition ((v/v) %):
Wet Dry CO2 80.0 90.9 8.0 9.1 1120 12.0 Total 100.0 100.0 (6) Combustion temperature is controlled by "coke" content and matrix properties.
Typically, HTO combustion T is between (380-800 C).
19 3.3 CSSOX
The CSSOX EOR process to recover heavy oil is similar to CSS (previously described) but oxygen gas is added during the steam-injection cycle (the "huff"). The "soak" and "puff' cycles are similar to CSS. Oxygen provides extra energy from combustion, and creates CO2 in the reservoir.
Figures 13 and 14 show how CSSOX can be conducted using an extra oxygen injection well or by segregating oxygen injection within the steam injection wells using separate tubing and a packer. Alternately, steam and oxygen can be injected at separate times, as long as oxygen injection follows steam, so the reservoir is preheated for auto-ignition of HTO combustion.
If we segregate oxygen injection near the top of the injector or using a separate 02 well, as shown in Figure 18 during the "huff' cycle we inject steam and oxygen;
during the "puff' cycle we can remove produced gases (mainly CO2) separately to better control the process.
3.4 SFOX
The SFOX EOR process to recover heavy oil is similar to SF (previously described) but oxygen gas is continuously injected near (or at) the steam injector to provide an added source of energy from in situ combustion. Steam + oxygen are injected in a vertical-well geometry, with producer/injector wells arranged in regular patterns.
Figures 9, 11 and 12 show how SFOX can be arranged. We can also use horizontal wells as shown in Figure 10, especially for the more viscous heavy oils.
The distinction between SF and SAGD process can sometimes be subtle. SAGD can be considered as a top-down steamflood, aided by gravity drainage. Figure 7 shows an
The CSSOX EOR process to recover heavy oil is similar to CSS (previously described) but oxygen gas is added during the steam-injection cycle (the "huff"). The "soak" and "puff' cycles are similar to CSS. Oxygen provides extra energy from combustion, and creates CO2 in the reservoir.
Figures 13 and 14 show how CSSOX can be conducted using an extra oxygen injection well or by segregating oxygen injection within the steam injection wells using separate tubing and a packer. Alternately, steam and oxygen can be injected at separate times, as long as oxygen injection follows steam, so the reservoir is preheated for auto-ignition of HTO combustion.
If we segregate oxygen injection near the top of the injector or using a separate 02 well, as shown in Figure 18 during the "huff' cycle we inject steam and oxygen;
during the "puff' cycle we can remove produced gases (mainly CO2) separately to better control the process.
3.4 SFOX
The SFOX EOR process to recover heavy oil is similar to SF (previously described) but oxygen gas is continuously injected near (or at) the steam injector to provide an added source of energy from in situ combustion. Steam + oxygen are injected in a vertical-well geometry, with producer/injector wells arranged in regular patterns.
Figures 9, 11 and 12 show how SFOX can be arranged. We can also use horizontal wells as shown in Figure 10, especially for the more viscous heavy oils.
The distinction between SF and SAGD process can sometimes be subtle. SAGD can be considered as a top-down steamflood, aided by gravity drainage. Figure 7 shows an
20 example of a hybrid process (SF and SAGD) where a vertical well is used as an injector and a lower horizontal well is used as a producer.
Gas (steam) override is an issue for SF processes. It may be advantageous in SFOX to include separate wells to remove non-condensable combustion gases as shown in Figure 16 or to segregate production as shown in Figure 17. Gas volumes are small and these wells need not be large (Table 3).
3.5 CSSOX/SFOX Advantages Because, many times, a CSS project can be converted to a SF project, or CSS is deliberately used as a start-up process for SF; the advantages of the steam +
oxygen version of each are similar ¨ as follows, comparing CSSOX and SFOX to their non-oxygen cousins:
(1) Lower energy costs (per unit heat delivered to the reservoir, oxygen gas costs less than steam).
(2) Reduced water use, per bbl. of production.
(3) More energy injected per unit volume of injectant gas. Table 1 shows that and equal mix (v/v) of oxygen and steam contains over 450 percent more energy than pure steam. This can increase production rates.
(4) Excess water production. A combustion process will mobilize connate water, in the combustion-swept zone, as steam. When produced, as water, this will contribute to an excess water production if all the injected steam is also produced as water.
(5) Combustion also produces water directly as a product of hydrocarbon oxidation.
(6) Carbon dioxide is produced by combustion. When CO2 dissolves into periphery heavy oil, it will provide a dissolved-gas-drive mechanism and add to production and to ultimate recovery (Balog (1982), Luo (2005)).
(7) Steam stimulates and helps HTO combustion (Moore (1994)).
(8) Steam also causes combustion to be more complete ¨ less CO more CO2.
Gas (steam) override is an issue for SF processes. It may be advantageous in SFOX to include separate wells to remove non-condensable combustion gases as shown in Figure 16 or to segregate production as shown in Figure 17. Gas volumes are small and these wells need not be large (Table 3).
3.5 CSSOX/SFOX Advantages Because, many times, a CSS project can be converted to a SF project, or CSS is deliberately used as a start-up process for SF; the advantages of the steam +
oxygen version of each are similar ¨ as follows, comparing CSSOX and SFOX to their non-oxygen cousins:
(1) Lower energy costs (per unit heat delivered to the reservoir, oxygen gas costs less than steam).
(2) Reduced water use, per bbl. of production.
(3) More energy injected per unit volume of injectant gas. Table 1 shows that and equal mix (v/v) of oxygen and steam contains over 450 percent more energy than pure steam. This can increase production rates.
(4) Excess water production. A combustion process will mobilize connate water, in the combustion-swept zone, as steam. When produced, as water, this will contribute to an excess water production if all the injected steam is also produced as water.
(5) Combustion also produces water directly as a product of hydrocarbon oxidation.
(6) Carbon dioxide is produced by combustion. When CO2 dissolves into periphery heavy oil, it will provide a dissolved-gas-drive mechanism and add to production and to ultimate recovery (Balog (1982), Luo (2005)).
(7) Steam stimulates and helps HTO combustion (Moore (1994)).
(8) Steam also causes combustion to be more complete ¨ less CO more CO2.
21 (9) If non-condensable gas is produced, it is mostly CO2 and suitable for capture and sequestration.
(10) For the same reservoir pressure, average temperatures will be higher.
Oxidation or HTO combustion occurs at 380-800 C, much higher than saturated steam temperatures for typical reservoir pressures (Ito 4 MPa).
(11) Up to a limit of oxygen injection, the heavy oil (residual coke) that is combusted is oil that would otherwise not be recovered (residual oil in the steam-swept zone).
(12) Steam-only processes leave behind residual oil (about 10% of the pore space).
Some of this oil is mobilized and recovered by the steam + oxygen processes.
(13) If some of the combustion CO2 is left-behind in the reservoir or if some of the produced CO2 is captured and sequestered, CSSOX or SFOX can have reduced CO2 emissions compared to their steam-only counterparts.
(14) As shown in Table 3, because oxygen carries about ten times the heat content, per unit volume, pipe sizes for CSSOX or SFOX wells can be much smaller than for steam-only processes.
(15) Table 3 also demonstrates for a wide range of oxygen + steam mixes, if we wish to deliver oxygen gas at a segregated section in an existing steam injector (e.g.
Figure 14), there is enough room for an oxygen tube and steam in the annulus, even for mixes as lean as 5% oxygen.
4. Preferred Embodiments 4.1 Heavy Oil This invention applies to heavy oil with some initial oil mobility and initial gas injectivity. It does not apply to bitumen (API<10) that is better suited to the SAGD-version SAGDOX (in a separate patent).
For the purpose of this document we will define "heavy oil" as between 10 API
and 20 API, with some initial gas injectivity in the reservoir.
(10) For the same reservoir pressure, average temperatures will be higher.
Oxidation or HTO combustion occurs at 380-800 C, much higher than saturated steam temperatures for typical reservoir pressures (Ito 4 MPa).
(11) Up to a limit of oxygen injection, the heavy oil (residual coke) that is combusted is oil that would otherwise not be recovered (residual oil in the steam-swept zone).
(12) Steam-only processes leave behind residual oil (about 10% of the pore space).
Some of this oil is mobilized and recovered by the steam + oxygen processes.
(13) If some of the combustion CO2 is left-behind in the reservoir or if some of the produced CO2 is captured and sequestered, CSSOX or SFOX can have reduced CO2 emissions compared to their steam-only counterparts.
(14) As shown in Table 3, because oxygen carries about ten times the heat content, per unit volume, pipe sizes for CSSOX or SFOX wells can be much smaller than for steam-only processes.
(15) Table 3 also demonstrates for a wide range of oxygen + steam mixes, if we wish to deliver oxygen gas at a segregated section in an existing steam injector (e.g.
Figure 14), there is enough room for an oxygen tube and steam in the annulus, even for mixes as lean as 5% oxygen.
4. Preferred Embodiments 4.1 Heavy Oil This invention applies to heavy oil with some initial oil mobility and initial gas injectivity. It does not apply to bitumen (API<10) that is better suited to the SAGD-version SAGDOX (in a separate patent).
For the purpose of this document we will define "heavy oil" as between 10 API
and 20 API, with some initial gas injectivity in the reservoir.
Claims (25)
1. A process to recover heavy oil from a hydrocarbon reservoir, said process comprising injecting oxygen-containing gas and steam separately injected via separate wells into the reservoir to cause heated hydrocarbon fluids to flow more readily to a production well, wherein:
(i) the hydrocarbon is heavy oil (API from about 10 to 20; with some initial gas injectivity (ii) the ratio of oxygen/steam injectant gas is controlled substantially in the range from 0.05 to 1.00 (v/v) (iii) the process uses Cyclic Steam Stimulation or Steam Flooding techniques and well geometry, with extra well(s) or a segregated zone to inject oxygen gas wherein the oxygen contact zone within the reservoir is less than substantially 50 metres long.
(i) the hydrocarbon is heavy oil (API from about 10 to 20; with some initial gas injectivity (ii) the ratio of oxygen/steam injectant gas is controlled substantially in the range from 0.05 to 1.00 (v/v) (iii) the process uses Cyclic Steam Stimulation or Steam Flooding techniques and well geometry, with extra well(s) or a segregated zone to inject oxygen gas wherein the oxygen contact zone within the reservoir is less than substantially 50 metres long.
2. The process of claim 1 wherein a separate well or segregation is used for non-condensable gas produced by combustion.
3. The process of claim 1 wherein the oxygen-containing gas has an oxygen content of 95 to 99.9% (v/v).
4. The process of claim 3 wherein the oxygen-containing gas has an oxygen content of 95 to 97% (v/v).
5. The process of claim 1 wherein the oxygen-containing gas is air.
6. The process of claim 5 wherein the oxygen-containing gas is enriched air with an oxygen content of substantially 20 to 95% (v/v).
7. The process of claim 1 wherein the oxygen injection well within the reservoir is less than substantially 50 metres long proximate a steam swept zone.
8. The process of claim 1 whereby the oxygen-containing gas injection step is started only after a steam-swept zone is formed around the injection point.
9. The process of claim 8 controlled by:
(i) adjusting steam and oxygen flow ratios to attain a target.
(ii) adjusting steam + oxygen flows to attain an energy rate target.
(i) adjusting steam and oxygen flow ratios to attain a target.
(ii) adjusting steam + oxygen flows to attain an energy rate target.
10. The process of claim 2 or 9 wherein a separate produced gas removal well is used to minimize steam override to production wells.
11. The process of claim 1 wherein oxygen/steam (v/v) ratios start at about 0.05 and ramp up to about 1.00 as the process matures.
12. The process of claim 1 or 2 where the oxygen/steam (v/v) ratio is held between 0.4 and 0.7 and most preferably .35.
13. The process of claim 1 wherein:
(i) the ratio of oxygen/steam (v/v) is between 0.4 and 0.7 (ii) the oxygen purity in the oxygen-containing gas is between 95 and 97%
(v/v).
(i) the ratio of oxygen/steam (v/v) is between 0.4 and 0.7 (ii) the oxygen purity in the oxygen-containing gas is between 95 and 97%
(v/v).
14. The process of claim 1 or 7 further comprising an injector well (either a separate vertical well or the segregated portion of a well) having a maximum perforated zone (or zone with slotted liners) of less than substantially 50 m so that oxygen flux rates can be maximized.
15. The process of claim 14 wherein Oxygen is injected proximate a steam-swept zone, whereby combustion of residual fuel in the reservoir is the source of energy for said combustion, said zone being preheated, at start-up, so spontaneous High Temperature Oxidation can occur.
16. An improved Cyclic Steam Stimulation Enhanced Oil Recovery process to recover heavy oil comprising adding oxygen gas during a typical steam-injection cycle (the "huff'), the "soak"
and "puff' cycles being similar to conventional CSS, wherein the injection of Oxygen provides extra energy from combustion of residual oil, for heavy oil recovery while creating CO2 in the reservoir and removing produced CO2 separately to better control the process.
and "puff' cycles being similar to conventional CSS, wherein the injection of Oxygen provides extra energy from combustion of residual oil, for heavy oil recovery while creating CO2 in the reservoir and removing produced CO2 separately to better control the process.
17. The process of claim 16 wherein an extra oxygen injection well is utilized.
18. The process of claim 16 further comprising segregating oxygen injection within steam injection wells using separate tubing and a packer.
19. The process of claim 16 wherein steam and oxygen are injected at separate times, as long as oxygen injection follows steam, so the reservoir is preheated for auto-ignition of High Temperature Oxidation combustion.
20. The process of claim 16 wherein;
oxygen injection is segregated near the top of the injector well or using a separate O2 well, during the "huff' cycle, by injecting steam and oxygen;
and during the "puff' cycle removing produced gases (mainly CO2) separately to better control the process.
oxygen injection is segregated near the top of the injector well or using a separate O2 well, during the "huff' cycle, by injecting steam and oxygen;
and during the "puff' cycle removing produced gases (mainly CO2) separately to better control the process.
21. The process of claim 16 wherein the CSSOX process is the startup process for a SFOX
process.
process.
22. An improved Steam Flooding (SFOX EOR) Enhanced Oil Recovery process to recover heavy oil, basically similar to a conventional SF process, the improvement comprising injection of oxygen gas continuously injected near (or at) the steam injector to provide an added source of energy from in situ combustion of residual fuels, said Steam and oxygen being injected in a vertical-well geometry, with producer/injector wells arranged in regular patterns.
23. The process of claim 22 wherein separated wells are provided to remove non-condensable combustion gases.
24. The process of claim 22 or 23 further comprising use of horizontal wells, especially for the more viscous heavy oils.
25. The process of claim 1, 16 or 22 wherein the pipe sizes for CSSOX or SFOX
wells can be much smaller than for steam-only processes because oxygen carries about ten times the heat content, per unit volume.
wells can be much smaller than for steam-only processes because oxygen carries about ten times the heat content, per unit volume.
Applications Claiming Priority (2)
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US201161550479P | 2011-10-24 | 2011-10-24 | |
US61/550,479 | 2011-10-24 |
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CA2791318A1 true CA2791318A1 (en) | 2013-04-24 |
Family
ID=48135022
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CA2791318A Abandoned CA2791318A1 (en) | 2011-10-24 | 2012-09-27 | Steam flooding with oxygen injection, and cyclic steam stimulation with oxygen injection |
Country Status (5)
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---|---|
US (1) | US20130098607A1 (en) |
CN (1) | CN103917744A (en) |
BR (1) | BR112014009440A2 (en) |
CA (1) | CA2791318A1 (en) |
WO (1) | WO2013059909A1 (en) |
Cited By (2)
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US9163491B2 (en) | 2011-10-21 | 2015-10-20 | Nexen Energy Ulc | Steam assisted gravity drainage processes with the addition of oxygen |
US9803456B2 (en) | 2011-07-13 | 2017-10-31 | Nexen Energy Ulc | SAGDOX geometry for impaired bitumen reservoirs |
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US9869169B2 (en) | 2013-12-12 | 2018-01-16 | Husky Oil Operations Limited | Method to maintain reservoir pressure during hydrocarbon recovery operations using electrical heating means with or without injection of non-condensable gases |
US10233727B2 (en) * | 2014-07-30 | 2019-03-19 | International Business Machines Corporation | Induced control excitation for enhanced reservoir flow characterization |
CN107130951B (en) * | 2017-05-17 | 2019-09-10 | 中国石油天然气股份有限公司 | The method and its system of situation are connected between a kind of monitoring steam flooding well |
CA2972203C (en) | 2017-06-29 | 2018-07-17 | Exxonmobil Upstream Research Company | Chasing solvent for enhanced recovery processes |
CA2974712C (en) | 2017-07-27 | 2018-09-25 | Imperial Oil Resources Limited | Enhanced methods for recovering viscous hydrocarbons from a subterranean formation as a follow-up to thermal recovery processes |
CA2978157C (en) | 2017-08-31 | 2018-10-16 | Exxonmobil Upstream Research Company | Thermal recovery methods for recovering viscous hydrocarbons from a subterranean formation |
CA2983541C (en) | 2017-10-24 | 2019-01-22 | Exxonmobil Upstream Research Company | Systems and methods for dynamic liquid level monitoring and control |
CN112302598B (en) * | 2020-11-20 | 2022-04-01 | 西南石油大学 | System and method for generating steam underground in ultra-deep heavy oil reservoir |
CN115478824A (en) * | 2021-06-16 | 2022-12-16 | 中国石油天然气股份有限公司 | Fire flooding huff and puff effect-inducing oil production method |
US20230160293A1 (en) * | 2021-11-23 | 2023-05-25 | Halliburton Energy Services, Inc. | Conversion of carbon dioxide captured from fracturing operation to formic acid used in fracturing fluid |
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-
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- 2012-09-27 CA CA2791318A patent/CA2791318A1/en not_active Abandoned
- 2012-09-27 CN CN201280052026.XA patent/CN103917744A/en active Pending
- 2012-09-27 US US13/628,178 patent/US20130098607A1/en not_active Abandoned
- 2012-09-27 WO PCT/CA2012/000898 patent/WO2013059909A1/en active Application Filing
- 2012-09-27 BR BR112014009440A patent/BR112014009440A2/en not_active Application Discontinuation
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US9803456B2 (en) | 2011-07-13 | 2017-10-31 | Nexen Energy Ulc | SAGDOX geometry for impaired bitumen reservoirs |
US9163491B2 (en) | 2011-10-21 | 2015-10-20 | Nexen Energy Ulc | Steam assisted gravity drainage processes with the addition of oxygen |
Also Published As
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BR112014009440A2 (en) | 2017-04-11 |
US20130098607A1 (en) | 2013-04-25 |
WO2013059909A1 (en) | 2013-05-02 |
CN103917744A (en) | 2014-07-09 |
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