CA1166150A - Method of improved oil recovery by simultaneous injection of water with an in-situ combustion process - Google Patents
Method of improved oil recovery by simultaneous injection of water with an in-situ combustion processInfo
- Publication number
- CA1166150A CA1166150A CA000400177A CA400177A CA1166150A CA 1166150 A CA1166150 A CA 1166150A CA 000400177 A CA000400177 A CA 000400177A CA 400177 A CA400177 A CA 400177A CA 1166150 A CA1166150 A CA 1166150A
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- Canada
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- reservoir
- water
- combustion
- oil
- oxygen
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Abstract
A METHOD OF IMPROVED OIL RECOVERY BY SIMULTANEOUS
INJECTION OF WATER WITH AN IN-SITU COMBUSTION PROCESS
ABSTRACT
In a method of recovering heavy oil from a subterranean, permeable, heavy oil-bearing reservoir, an oxygen-containing gas is injected into the lower portion of the reservoir to establish an in-situ combustion reaction therein and to form a combustion front near the injection well. Injection of the oxygen-containing gas is continued to advance the combustion front that heats the oil and generates gas to displace the oil through the reservoir towards a producing well. Water is injected into the upper portion of the reservoir during combustion to prevent gases from migrating into the upper portion of the reservoir, scavenge heat from the combustion-heated portion of the reservoir, and displace oil from the reservoir, particularly the lower region, towards the production well. The areal sweep efficiency of the injected water may be improved by the addition of thickening agents and water-soluble polymers.
INJECTION OF WATER WITH AN IN-SITU COMBUSTION PROCESS
ABSTRACT
In a method of recovering heavy oil from a subterranean, permeable, heavy oil-bearing reservoir, an oxygen-containing gas is injected into the lower portion of the reservoir to establish an in-situ combustion reaction therein and to form a combustion front near the injection well. Injection of the oxygen-containing gas is continued to advance the combustion front that heats the oil and generates gas to displace the oil through the reservoir towards a producing well. Water is injected into the upper portion of the reservoir during combustion to prevent gases from migrating into the upper portion of the reservoir, scavenge heat from the combustion-heated portion of the reservoir, and displace oil from the reservoir, particularly the lower region, towards the production well. The areal sweep efficiency of the injected water may be improved by the addition of thickening agents and water-soluble polymers.
Description
A METHOD OF IMPROVED OIL RECOVERY BY SIM[JL~NEOUS
INJECTION OF W~ ;K WITH AN IN-SITU a)MBUSTION PROCESS
m is invention concerns a thermal oil recovery method utilizing in-situ combustion which permits efficient recovery of heavy oil from permeable, heavy oil-bearing reservoirs.
It has been proposed to recover oil, in the nature of heavy viscous oils, from a subterranean reservoir by a method which is commonly known as in-situ combustion. In this method, an oxygen-containing gas is injected into the reservoir through an injection well with ignition of oil within the adjacent reservoir initiated by suitable means for establishing a combustion front.
m e reservoir is usually provided with one or more production wells for the production of oil. As the flow of oxygen-containing gas to the reservoir is continued, the combustion front is moved from the injection well toward the production wells. m e heat generated by burning reduces the viscosity of the oil which is displaçed before the combustion front toward the production wells from which the oil is recovered. m e combustion front in displacing the mobile oil before it in the reservoir uses residual carbonaceous deposits as fuel.
In this known process, the gaseous combustion products and light hydrocarbons are considerably lighter than the oil and water present in the reservoir and thus, because of gravity segregation, tend to rise to the top of the reservoir when vertical communication exists. Consequently, these products channel through the top of the formation to the producing well thereby over-riding a major portion of the reservoir and contacting only a small fraction of the reservoir oil. This behavior results in inefficient oil recovery and low vertical sweep efficiency.
Furthermore, in such in-situ combustion processes, large quantities of heated rock are left behind in the reservoir. m is heat is therefore lost, which greatly reduces the thermal efficiency of the process.
~, -According to the present invention, there is provided an improved method for recovering oil, especially viscous or heavy oil, from a permeable, heavy oil-bearing reservoir wherein in-situ combustion is established in the lower portion of the reservoir, water is injected into the upper portion of the formation at a controlled rate and oil is recovered at a production well. An oxidizing gas such as air or oxygen or mixtures thereof is injected into the lower portion of the reservoir to form a combustion front which advances through the reservoir toward a production well. Heat generated by the in-situ combustion reaction heats the viscous oil as it advances through the reservoir thereby reducing its viscosity. The higher density water injected above the in-situ combustion front tends to segregate to the bottom of the reservoir because of gravitational forces, whereas the lower density products of combustion tend to segregate to the top. In addition to effective contact and heat exchange between the water and the gaseous products of combustion, the water tends to fill gas-swept channels thus impeding the flow of gases and diverting them to previously unswept paths resulting in higher vertical sweep efficiency. m e water passing through the combustion-heated formation scavenges heat and becomes a hot water drive displacing oil fr~m lower regions, not subjected to combustion, which further improves recovery efficiency per BTU of heat injected. mis type of vertical crossflow of fluids within a reservoir enables the reservoir to be more efficiently heated over the areal extent of the reservoir thereby greatly enhancing the recovery of oil. Mobility control agents such as thickeners and water-soluble polymers may be added to the injected water to improve its areal sweep efficiency.
The accompanying drawing is a cross-sectional view of an injection well and a production well penetrating a subterranean, permeable, heavy oil-bearing reservoir from which oil is to be recovered by a method according to one example of the invention.
Referring to the drawing, a subterranean, permeable, heavy oil-bearing reservoir 10, is overlain by overburden 12 and underlain il50 F-0938 ~3~
by basement formation 14. m e reservoir 10 is penetrated by an injection well 16 and a production well 18.
m e injection well 16 has perforations 20 providing fluid communication with the upper portion of reservoir 10 and perforations 22 providing fluid communication with the lower portion of the reservoir. A tubing string 24 extends from the earth's surface to the lower portion of reservoir 10 forming an annular space 26 between the tubing string and injection well casing 28.
A packer 30 seals the outer tubing surface from the inside of casing 28. The top of injection well 16 is provided with means 31 for injecting fluid into the annular space 26 between tubing 24 and casing 28.
The production well 18 has perforations 32 providing fluid communication with the lower portion of reservoir 10 for the recovery of oil and gases through conduit 34 to the surface of the earth.
According to a preferred mode of operation, the lower portion of the oil-bearing reservoir 10 is ignited in the vicinity of perforations 22. After ignition, an oxygen-containing gas such as oxygen or air or mixtures thereof is injected through tubing string 24 into the lower portion of the reservoir through perforations 22. A combustion front is formed which progressively advances from the injection well to the production well. After the combustion front has advanced a sufficient distance, water is injected through injection means 31 into the space 26 formed between casing 28 and tubing 24 and outwardly through the perforations 20 into the upper portion of the reservoir 10.
m e water, since it has a relatively high density, tends to segregate to the bottom of the formation because of gravitational forces, whereas the relatively low density combustion gases tend to segregate to the top. m e water also tends to fill gas-swept channels thus impeding the flow of gas and diverting it to previously unswept paths resulting in higher vertical sweep efficiency. The water passing through the combustion-heated F-0938 ~4~
reservoir scavenges heat and becomes a hot water drive displacing oil from lower regions of the reservoir, not subjected to combustion, which further improves recovery efficiency.
m e combustion front and water advance through the reservoir 10 contacting the oil and reducing its viscosity and displacing the oil towards production well 18. Admixtures of oil and gases enter production well 18 through the lower perforations 32, pass up through conduit 34 and are recovered at the surface of the earth.
Once the combustion front is sufficiently near to the production well which can be ascertained by a rise in the tem~erature at the production well, further injection of the oxidizing gas is discontinued. Water injection may be continued until water breaks through at the production well 18.
Water may be injected with the oxygen-containing combustion supporting gas after the initiation of in-situ combustion so as to absorb heat from the combustion 20ne, which is a technique known in the art as wet combustion. The amount of water injected, in relation to the oxygen-containing combustion supporting gas, will vary depending upon the a unt necessary to keep the reservoir below excessive temperature levels. It must not be so great, of course, as to extinguish combustion as would be evidenced by the composition of the gases produced from the reservoir.
The oxygen-containing gas used to support combustion can be air, substantially pure oxygen, or oxygen-enriched air.
The amount of water injected into the upper portion of the reservoir is much larger than that used in conventional wet combustion processes in order to scavenge sufficient heat from the burned out portion of the reservoir and also to restrict gas flow in the burned zone. However, the injection rate must be controlled or intermittently discontinued to prevent the water from overriding the combustion front or extinguishing it. m e st appropriate amount of water injected into the upper portion of the reservoir may vary over a wide range depending on many factors such as reservoir, oil F-0938 ~5~
zone thickness, well spacing, reservoir permeability, and other variables of operation such as the rate of air injection to support the combustion process. In general, however, where air is injected into the low portion of the reservoir, the water injected into the upper portion will be in the range 0.1 to 2.0, more preferably 0.3 to 1.0, barrels of water per 1000 cubic feet of air injected.
In another embodiment of the invention, separate injection wells may be used for the injection of the oxidizing gas such as air or oxygen and water into the selected portions of the reservoir.
For example, two or more closely spaced injection wells may be used with air or oxygen injected near the bottom of the reservoir through one well and water injected near the top of all, or selected, separate wells as dictated by preferred engineering practices.
In another embodiment of the process of this invention, the areal sweep efficiency of the water injected into the upper portion of the reservoir may be improved by the addition thereto of mobility control agents such as thickeners or water-soluble polymers. m ese agents increase the viscosity of the water and hence decrease its bility with a resulting increase in displacement efficiency.
Examples of thickeners and water-soluble polymers useful in connection with this process are disclosed in U. S. Patent Nos.
3,500,918 to Holm and 3,710,861 to Steeg, m e present invention may be carried out utilizing any suitable injection and production system. m e injection and production systems may comprise one or more wells extending from the surface of the earth into the oi~-bearing formation. Such injection and production wells may be located and spaced from one another in any desired pattern. For example, a line drive pattern may be utilized in which a plurality of injection wells are arranged in a more or less straight line toward a plurality of production wells in a more or less straight line parallel to a line intersecting the plurality of injection wells. In addition, a circular drive pattern may be used in which the injection system comprises a central injection well and the production system comprises a plurality of production wells about the injection well in a ring pattern such as a 5-spot or 7-spot well pattern.
INJECTION OF W~ ;K WITH AN IN-SITU a)MBUSTION PROCESS
m is invention concerns a thermal oil recovery method utilizing in-situ combustion which permits efficient recovery of heavy oil from permeable, heavy oil-bearing reservoirs.
It has been proposed to recover oil, in the nature of heavy viscous oils, from a subterranean reservoir by a method which is commonly known as in-situ combustion. In this method, an oxygen-containing gas is injected into the reservoir through an injection well with ignition of oil within the adjacent reservoir initiated by suitable means for establishing a combustion front.
m e reservoir is usually provided with one or more production wells for the production of oil. As the flow of oxygen-containing gas to the reservoir is continued, the combustion front is moved from the injection well toward the production wells. m e heat generated by burning reduces the viscosity of the oil which is displaçed before the combustion front toward the production wells from which the oil is recovered. m e combustion front in displacing the mobile oil before it in the reservoir uses residual carbonaceous deposits as fuel.
In this known process, the gaseous combustion products and light hydrocarbons are considerably lighter than the oil and water present in the reservoir and thus, because of gravity segregation, tend to rise to the top of the reservoir when vertical communication exists. Consequently, these products channel through the top of the formation to the producing well thereby over-riding a major portion of the reservoir and contacting only a small fraction of the reservoir oil. This behavior results in inefficient oil recovery and low vertical sweep efficiency.
Furthermore, in such in-situ combustion processes, large quantities of heated rock are left behind in the reservoir. m is heat is therefore lost, which greatly reduces the thermal efficiency of the process.
~, -According to the present invention, there is provided an improved method for recovering oil, especially viscous or heavy oil, from a permeable, heavy oil-bearing reservoir wherein in-situ combustion is established in the lower portion of the reservoir, water is injected into the upper portion of the formation at a controlled rate and oil is recovered at a production well. An oxidizing gas such as air or oxygen or mixtures thereof is injected into the lower portion of the reservoir to form a combustion front which advances through the reservoir toward a production well. Heat generated by the in-situ combustion reaction heats the viscous oil as it advances through the reservoir thereby reducing its viscosity. The higher density water injected above the in-situ combustion front tends to segregate to the bottom of the reservoir because of gravitational forces, whereas the lower density products of combustion tend to segregate to the top. In addition to effective contact and heat exchange between the water and the gaseous products of combustion, the water tends to fill gas-swept channels thus impeding the flow of gases and diverting them to previously unswept paths resulting in higher vertical sweep efficiency. m e water passing through the combustion-heated formation scavenges heat and becomes a hot water drive displacing oil fr~m lower regions, not subjected to combustion, which further improves recovery efficiency per BTU of heat injected. mis type of vertical crossflow of fluids within a reservoir enables the reservoir to be more efficiently heated over the areal extent of the reservoir thereby greatly enhancing the recovery of oil. Mobility control agents such as thickeners and water-soluble polymers may be added to the injected water to improve its areal sweep efficiency.
The accompanying drawing is a cross-sectional view of an injection well and a production well penetrating a subterranean, permeable, heavy oil-bearing reservoir from which oil is to be recovered by a method according to one example of the invention.
Referring to the drawing, a subterranean, permeable, heavy oil-bearing reservoir 10, is overlain by overburden 12 and underlain il50 F-0938 ~3~
by basement formation 14. m e reservoir 10 is penetrated by an injection well 16 and a production well 18.
m e injection well 16 has perforations 20 providing fluid communication with the upper portion of reservoir 10 and perforations 22 providing fluid communication with the lower portion of the reservoir. A tubing string 24 extends from the earth's surface to the lower portion of reservoir 10 forming an annular space 26 between the tubing string and injection well casing 28.
A packer 30 seals the outer tubing surface from the inside of casing 28. The top of injection well 16 is provided with means 31 for injecting fluid into the annular space 26 between tubing 24 and casing 28.
The production well 18 has perforations 32 providing fluid communication with the lower portion of reservoir 10 for the recovery of oil and gases through conduit 34 to the surface of the earth.
According to a preferred mode of operation, the lower portion of the oil-bearing reservoir 10 is ignited in the vicinity of perforations 22. After ignition, an oxygen-containing gas such as oxygen or air or mixtures thereof is injected through tubing string 24 into the lower portion of the reservoir through perforations 22. A combustion front is formed which progressively advances from the injection well to the production well. After the combustion front has advanced a sufficient distance, water is injected through injection means 31 into the space 26 formed between casing 28 and tubing 24 and outwardly through the perforations 20 into the upper portion of the reservoir 10.
m e water, since it has a relatively high density, tends to segregate to the bottom of the formation because of gravitational forces, whereas the relatively low density combustion gases tend to segregate to the top. m e water also tends to fill gas-swept channels thus impeding the flow of gas and diverting it to previously unswept paths resulting in higher vertical sweep efficiency. The water passing through the combustion-heated F-0938 ~4~
reservoir scavenges heat and becomes a hot water drive displacing oil from lower regions of the reservoir, not subjected to combustion, which further improves recovery efficiency.
m e combustion front and water advance through the reservoir 10 contacting the oil and reducing its viscosity and displacing the oil towards production well 18. Admixtures of oil and gases enter production well 18 through the lower perforations 32, pass up through conduit 34 and are recovered at the surface of the earth.
Once the combustion front is sufficiently near to the production well which can be ascertained by a rise in the tem~erature at the production well, further injection of the oxidizing gas is discontinued. Water injection may be continued until water breaks through at the production well 18.
Water may be injected with the oxygen-containing combustion supporting gas after the initiation of in-situ combustion so as to absorb heat from the combustion 20ne, which is a technique known in the art as wet combustion. The amount of water injected, in relation to the oxygen-containing combustion supporting gas, will vary depending upon the a unt necessary to keep the reservoir below excessive temperature levels. It must not be so great, of course, as to extinguish combustion as would be evidenced by the composition of the gases produced from the reservoir.
The oxygen-containing gas used to support combustion can be air, substantially pure oxygen, or oxygen-enriched air.
The amount of water injected into the upper portion of the reservoir is much larger than that used in conventional wet combustion processes in order to scavenge sufficient heat from the burned out portion of the reservoir and also to restrict gas flow in the burned zone. However, the injection rate must be controlled or intermittently discontinued to prevent the water from overriding the combustion front or extinguishing it. m e st appropriate amount of water injected into the upper portion of the reservoir may vary over a wide range depending on many factors such as reservoir, oil F-0938 ~5~
zone thickness, well spacing, reservoir permeability, and other variables of operation such as the rate of air injection to support the combustion process. In general, however, where air is injected into the low portion of the reservoir, the water injected into the upper portion will be in the range 0.1 to 2.0, more preferably 0.3 to 1.0, barrels of water per 1000 cubic feet of air injected.
In another embodiment of the invention, separate injection wells may be used for the injection of the oxidizing gas such as air or oxygen and water into the selected portions of the reservoir.
For example, two or more closely spaced injection wells may be used with air or oxygen injected near the bottom of the reservoir through one well and water injected near the top of all, or selected, separate wells as dictated by preferred engineering practices.
In another embodiment of the process of this invention, the areal sweep efficiency of the water injected into the upper portion of the reservoir may be improved by the addition thereto of mobility control agents such as thickeners or water-soluble polymers. m ese agents increase the viscosity of the water and hence decrease its bility with a resulting increase in displacement efficiency.
Examples of thickeners and water-soluble polymers useful in connection with this process are disclosed in U. S. Patent Nos.
3,500,918 to Holm and 3,710,861 to Steeg, m e present invention may be carried out utilizing any suitable injection and production system. m e injection and production systems may comprise one or more wells extending from the surface of the earth into the oi~-bearing formation. Such injection and production wells may be located and spaced from one another in any desired pattern. For example, a line drive pattern may be utilized in which a plurality of injection wells are arranged in a more or less straight line toward a plurality of production wells in a more or less straight line parallel to a line intersecting the plurality of injection wells. In addition, a circular drive pattern may be used in which the injection system comprises a central injection well and the production system comprises a plurality of production wells about the injection well in a ring pattern such as a 5-spot or 7-spot well pattern.
Claims (13)
1. A method for recovering oil from a subterranean, permeable, oil-bearing reservoir comprising the steps of:
a. establishing a combustion zone in the lower portion of said reservoir at the face of an injection well penetrating said reservoir;
b. injecting an oxygen-containing gas into the lower portion of said reservoir via said injection well to move said combustion zone toward a producing well penetrating said reservoir and to generate hot combustion gases;
c. injecting water via an injection well penetrating said reservoir into the upper portion of said reservoir to impede the flow of said hot combustion gases through the upper portion of the reservoir, to scavenge heat from the combustion heated portion of the formation, and to displace oil through said reservoir towards said production well; and d. recovering oil from said production well.
a. establishing a combustion zone in the lower portion of said reservoir at the face of an injection well penetrating said reservoir;
b. injecting an oxygen-containing gas into the lower portion of said reservoir via said injection well to move said combustion zone toward a producing well penetrating said reservoir and to generate hot combustion gases;
c. injecting water via an injection well penetrating said reservoir into the upper portion of said reservoir to impede the flow of said hot combustion gases through the upper portion of the reservoir, to scavenge heat from the combustion heated portion of the formation, and to displace oil through said reservoir towards said production well; and d. recovering oil from said production well.
2. The method as defined in Claim 1 wherein said oxygen-containing gas is air.
3. The method as defined in Claim 1 wherein said oxygen-containing gas is oxygen-enriched air.
4. The method as defined in Claim 1 wherein said oxygen-containing gas is substantially pure oxygen.
5. The method as defined in Claim 1 and further comprising injecting water simultaneously with said oxygen-containing gas during step (b) so as to absorb heat from the combustion zone without extinguishing the combustion zone.
6. The method as defined in Claim 1 wherein the water injected into the upper portion of the reservoir during step (c) contains a thickening agent to increase its viscosity.
7. The method as defined in Claim 1 wherein the water injected into the upper portion of the reservoir during step (c) contains a water-soluble polymer to increase its viscosity.
8. m e method as defined in Claim 1 wherein the injection of water in step (c) is periodically terminated.
9. A method for recovering oil from a subterranean, permeable, oil-bearing reservoir penetrated by an injection well and a production well comprising:
a. establishing in-situ combustion in the lower portion of the reservoir and advancing the combustion zone through the reservoir toward the production well;
b. injecting water into the upper portion of the reservoir; and c. recovering oil from the production well.
a. establishing in-situ combustion in the lower portion of the reservoir and advancing the combustion zone through the reservoir toward the production well;
b. injecting water into the upper portion of the reservoir; and c. recovering oil from the production well.
10. The method as defined in Claim 9 and further comprising injecting water via said injection well into the combustion zone so as to absorb heat from the combustion zone without extinguishing the combustion.
11. The method as defined in Claim 9 wherein said water injected into the upper portion of the reservoir contains a thickening agent to increase its viscosity.
12. The method as defined in Claim 9 wherein said water injected into the upper portion of the reservoir contains a water-soluble polymer to increase its viscosity.
13. The method as defined in Claim 9 wherein the injection of water into the upper portion of the reservoir is periodically terminated.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US25933081A | 1981-04-30 | 1981-04-30 | |
| US259,330 | 1981-04-30 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1166150A true CA1166150A (en) | 1984-04-24 |
Family
ID=22984496
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000400177A Expired CA1166150A (en) | 1981-04-30 | 1982-03-31 | Method of improved oil recovery by simultaneous injection of water with an in-situ combustion process |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1166150A (en) |
-
1982
- 1982-03-31 CA CA000400177A patent/CA1166150A/en not_active Expired
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