CA1194783A - Method of recovering oil from a viscous oil- containing subsurface formation - Google Patents
Method of recovering oil from a viscous oil- containing subsurface formationInfo
- Publication number
- CA1194783A CA1194783A CA000419021A CA419021A CA1194783A CA 1194783 A CA1194783 A CA 1194783A CA 000419021 A CA000419021 A CA 000419021A CA 419021 A CA419021 A CA 419021A CA 1194783 A CA1194783 A CA 1194783A
- Authority
- CA
- Canada
- Prior art keywords
- oil
- formation
- production well
- fluid
- solvent
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Abstract
A METHOD OF RECOVERING OIL FROM A VISCOUS
OIL-CONTAINING SUBSURFACE FORMATION
Abstract Oil is recovered from a viscous oil-containing formation, including a tar sand deposit, by first establishing a fluid communication path 18 in the lower portion of the formation 10 intermediate at least one injection well 12 and a production well 14.
A hydrocarbon solvent having a density less than oil contained in the formation and a viscosity not greater than 1/100 the viscosity of the oil contained in the formation under formation conditions is injected into the communication path 18 and fluids including oil are recovered from the production well 14 until the fluid recovered contains an unfavorable ratio of oil to solvent. The production well 14 is then shut-in and an additional quantity of the hydrocarbon solvent is injected into the fluid communication path 18, preferably until a total amount of between 0.05 to 0.30 pore volume. The injection well 12 is then shut-in along with the production well 14 to permit the formation to undergo a soak period for a variable time, preferably for a time of between 2 to 20 days per vertical thickness in feet of oil-containing formation 10. A driving fluid such as water is then injected into the formation 10 via the injection well 12 and the oil is produced until there is an unfavorable ratio of oil to driving fluid. During the fluid drive recovery phase, the injection well 12 and production well 14 may be completed to be in fluid communication with the entire portion of the formation to obtain a more uniform displacement of the upgraded formation oil by the driving fluid.
OIL-CONTAINING SUBSURFACE FORMATION
Abstract Oil is recovered from a viscous oil-containing formation, including a tar sand deposit, by first establishing a fluid communication path 18 in the lower portion of the formation 10 intermediate at least one injection well 12 and a production well 14.
A hydrocarbon solvent having a density less than oil contained in the formation and a viscosity not greater than 1/100 the viscosity of the oil contained in the formation under formation conditions is injected into the communication path 18 and fluids including oil are recovered from the production well 14 until the fluid recovered contains an unfavorable ratio of oil to solvent. The production well 14 is then shut-in and an additional quantity of the hydrocarbon solvent is injected into the fluid communication path 18, preferably until a total amount of between 0.05 to 0.30 pore volume. The injection well 12 is then shut-in along with the production well 14 to permit the formation to undergo a soak period for a variable time, preferably for a time of between 2 to 20 days per vertical thickness in feet of oil-containing formation 10. A driving fluid such as water is then injected into the formation 10 via the injection well 12 and the oil is produced until there is an unfavorable ratio of oil to driving fluid. During the fluid drive recovery phase, the injection well 12 and production well 14 may be completed to be in fluid communication with the entire portion of the formation to obtain a more uniform displacement of the upgraded formation oil by the driving fluid.
Description
~9f~ 33 F-1089 -l-A METHOD OF RECOVERING OIL FROM A VISCOUS
OIL-CONTAINING SUBSURFACE FORMATION
This invention is directed to a method of recovering oil from a viscous oil-containing subsurface formation. More particularly, this invention is directed to a hydrocarbon solvent recovery method for recovering oil from a subsurface formation which is penetrated by at least one injection well and one production well which extend from the surface of the earth and into the subsurface formation containing viscous hydrocarbons.
In U.S. Patent No. 4~293,035 of John L. Fitch, lssued October 6, 1981, there is disclosed a method of reca~ering viscous oil from 3 viscous oil-bearing subsurface formation wherein a solvent is injected into a high mobility channel formed in the bottom of the formation intermediate an injection well and a production well.
The solvent is injected until the ratio of produced oil to solvent becomes unfavorable and thereafter the injection of solvent is terminated and gas is injected into the high mobility channel to produce solvent and oil from the formation.
In U.S. Patent 3,838,738 there is described a method for recovering viscous petroleum from petroleum-containing formations by first establishing a fluid communication path low in the formationO A
heated fluid is then injected into the fluid communication path followed by injecting a volatile solvent such as carbon disulfide, benzene or toluene into the preheated flow path and continuing injecting the heating fluid and recovering fluids including petroleum from the production on well.
In U.S. Patent 3,500,917 there is disclosed a method for recovering crude oil from an oil-bearing formation having a water-saturated zone underlying the oil-saturated zone. A mixture of an aqueous fluid which has a density greater than the density of the crude oil and a solvent having a density less than the density of the crude oil are injected into the water-saturated zone and oil is produced ~rom the formation.
U.S. Patent 4,026,358 discloses a method for recovering heavy oil from a subterranean hydrocarbon-bearing formation traversed by at least one injection well and one production well wherein a slug of hydrocarbon solvent in amounts of 0.1 to about 20 percent o~ the formation pure volume and having a gas dissolved therein is injected into the ~ormation via the injection well. Thereafter, a thermal sink is created in the formation by in-situ combustion or by injecting steam. The wells are then shut in for a predetermined time to permit the formation to undergo a soak period, after which production is continued. Optionally, after the production period, the formation may be water flooded to recover additional oil from the formation.
This invention is directed to a method of recovering viscous oil from a viscous oil-containing formation that has no significant vertical permeability barrier in the portion of the formation to be tested and which is penetrated by at least one injection well and one production well. A fluid communication path is established through the lower portion of the subsurface formation intermediate the injection well and the production well, and a hydrocarbon solvent for the viscous oil having a viscosity not greater than 1/100 the viscosity of the oil contained in the formation under formation conditions and a specific gravity less than the oil contained in the formation, is injected via the injection well into this path and fluids including oil are recovered from the production well until the produced fluid contains an unfavorable ratio of oil to solvent. When this occurs, the production well is shut-in snd an additional quantity of hydrocarbon solvent, which is liquid under formation conditions, is injected into the formation via the injection well and through the fluid communication path, preferably until a total amount within the range of 0.05 to 0.30 pore volume has been injected. Thereafter, the injecticn well is shut-in along with the shut-in production well to permit the formation to undergo a soak period for a variable time, preferably for a period of time between 2 to 20 days per vertical thickness in feet of the viscous oil-containing formation. During this soak period, the light hydrocarbon solvent will tend to rise and the heavy oil will move F-1089 ~3 downward in a gravity-driven convection process forming a pattern of fingers. This fingering causes a more effective contact between the oil and solvent thus providing a greater volume of oil that is reduced in viscosity and which can be produced more readily. Thereafter, a driving fluid such as water is injected into the injection well to displace the mixture of oil and solvent toward the production well for recovery. Production is continued until the fluid including oil recovered from the production well contains an unfavorable ratio of oil to driving fluid.
The term "viscous oil~' is used herein to identify oil having relatively high viscosity and includes those oils referred to as tars.
Such viscous oils are also referred to as heavy oils. In general, the term viscous oil is used to include those heavy oils and tars such as are commonly found in formations referred to as heavy oil or tar sands that have viscosities that are great enough to severely restrict the production of the oils from the formations in which they are found.
The API gravity of such viscous oils is normally 20 API or less.
The accompanying drawing is a cross-sectional view illustrating a method according to one example of the invention of recovering oil from a subsurface oil-containing formation.
Referring to the drawing, a viscous oil bearing formation 10 that has no significant vertical p~ il;ty barriers is penetrated by an injection well 12 and a production well 14. The injection well 12 and production well 14 are perforated or fluid flow communication is otherwise established only adjacent the lower portion of the viscous oil-containing formation, and preferably only in the lower lû percent or less of the formation designated as 16 in the drawing. A fluid communication path 18 is established intel ~;ate the injection and production wells 12 and 14 through the lower portion of the viscous oil-containing formation 10. Thereafter, a hydrocarbon solvent having a specific gravity less than the specific gravity of the oil contained in the formation and having a viscosity not greater than 1/100 of the viscosity of the oil contained in the formation under formation conditions is injected via the injection well 12 through the fluid 7~33 communication path 18 and fluid including oil is recovered from the formation via production well 14. Solvent injection is continued until the fluid being recovered from the production well 14 comprises an unfavorable ratio of oil to solvent.
Thereafter, production well 14 is shut-in and an additional quantity of hydrocarbon solvent, which is liquid under formation conditions, is injected into the lower portion of the formation via the injection well 12 through the fluid communication path 18. The total amount of solvent injected is preferably within the range of 0.05 to 0~30 pore volume. Once this amount of solvent has been injected, the injection well 12 is shut-in along with the shut-in production well 14 and the formation is permitted to undergo a soak period for a variable time, preferably for a period of time between 2 to 2û days per vertical thickness in feet of the viscous oil-containing formation. It will be recognized by those skilled in the art of oil recovery that during this shut-in or soak period minor amounts of injection or production fluid, such as for the purpose of testing, may be done without significant detrimental effects on the process. Guring the soak period, the liquid hydro~arbon solvent being lighter than the oil contained in the viscous oil-~ontaining formation, that is, having a specific gravity less than the specific gravity of the oil contained in the formation and having a viscosity not greater than lJlûO of the viscosity of the oil contained in the formation under formation conditions, will tend to flow by gravity-driven convection upward into the oil containing formation and the neavy oil will flow by gravity-driven convection downward to form a hydrocarbon solvent-oil convection pattern as shown by the dashed lines 20 in the drawing. Furthermore, because of viscous instabilities, the rising hydrocarbon solvent and descending heavy oil form a pattern of fingers. This fingering is important in that the distribution, size and extension of these fingers will provide intimate contact between the solvent and the heavy oil allowing the two to mix more effectively, thus forming a greater volume of oil that is reduced in viscosity and which can be produced more readily. This relatively low viscosity mixture can be much more effectively displaced from the reservoir than F-1089 ~5~
the original heavy oil by flooding the formation with water or other suitable fluid, as is well known to those skilled in the art of petroleum engineering.
Once the soak period has been completed, a driving fluid is injected into the fluid communication path 18 via the injection well 12 and fluid including oil and hydrocarbon solvent is recovered from the production well 14. It is preferred that additional per~orations may be added to the injection well 12 or the production well 18, or both if desired, to establish fluid communication in both wells throu~hout the entire portion of the formation and thus obtain a more uniform displacement of the mobilized reservoir oils by the driving fluid. The driving fluid displaces both the oil and hydrocarbon solvent from the viscous oil-containing formation into the production well 14 and production is continued until the recovered Fluid contains an unfavorable ratio of oil to driving fluid. The driving fluid may be gaseous or liquid. For example, suitable gases include light aliphatic h~dlocarbu(,s having from one to four carbon atoms; carbon dioxide and nitr~gen may be used. However, aqueous fluids are partlcularly pre-ferred as the driv mg fluid, wqth water, brine and thickened aqueous 1uids all being suitable aque~us ~luids.
The fluid communication path 18 through the lower portion of the viscous oil-containing subsurface formation may be formed by injecting brine having a specific gravity greater than the specific gravity of the oil into the subsurface formation via the injection well 12 and through the perforations therein and into the oil-containing subsurface formation until the brine breaks through at the production well 14. In some formations brine may underlie the oil contained in the subsurface formation. In such cases, an oil-water contact will exist in the formation 10 and no additional brine need be injected into the formation to establish the fluid communication path 18. In such cases, it will be appreciated that the fluid communication path 18 is established by determining the existence of the oil-water contact and the brine-filled portion of the formation that underlies the oil 7~3;3 contained therein and communicates with the injection and the production well.
In the case of an oil-containing formation that is underlain by water and thus has an oil-water contact, the injection well is perforated and the perforation interval is provided adjacent the underlying water. Desirably, the upper perforations of this perforation interval are located about adjacent the oil-water contact though it could extend somewhat above this oil-water contact without seriously affecting the efficiency of the present recovery method. The production well is perforated and the perforation interval is provided adjacent the oil-water contact such that the lower perforation of this interval is located slightly above the oil-water contact. Again, in the case of a formation underlain by water, as it was with the formation that was not underlain by water, the perforation intervals that are provided in the injection and production wells desirably are no longer than about 10 percent of the total thickness of the vlscous oil-containing formation.
In the case of a formation underlain by brine which forms a fluid communication path between the injection and production well~s, the hydrocarbon solvent is selected to have a specific gravity less than that of the brine in addition to being less than that of the oil contained in the viscous oil-containing formation. The hydrocarbon solvent is in~ected via the injection well into this brine-filled fluid communication path and the process is continued in the same manner described above for the formation which is not underlain by water.
The hydrocarbon solvents used in the process of the invention should have a specific gravity less than that of the oil and less than that of the brine injected or naturally present in the formation and a visco~ity not greater than 1/100 the viscosity of the oil contained in the formation under formation conditions. It is also highly desirable that the hydrocarbon solvent remain liquid under the temperature and pressure conditions that exist in the subsurface viscous oil-containing formation and not cause solids such as asphaltenes to precipitate from the oil in amounts sufficient to seriously plug the pores of the formation. The preferred hydrocarbon solvent is a light crude oil.
Other examples of suitable hydrocarbon solvents include light oil condensates having an API gravity greater than 30 API degrees and partially refined tar which is generally known as syncrude. It may be desirable to include in the hydrocarbon solvent up to about 10 percent of aromatic material such as aromatic refinery stock to make the solvent compatible with the oil contained in the formations and to prevent the deposition of solid or gelatinous materials such as asphaltenes therefrom.
The viscous oil-containing subsurface formation to be treated by the present hydrocarbon solvent recovery method should be one that has no significant vertical permeab;lity barriers in that portion of the formation to be treated. This allows the solvent that is injected into the fluid communication path formed bet~leen the injection well and production well to flow upward into the formation by convection forces thus solllh;li7ing the oil and forming a solvent-oil mi~ture of reduced viscosity that can be more readily produced by a fluid drive process.
The method according to the invention is not restricted to the use in the field in which only two wells penetrate the formation. Any other number of wells, which may be arranged according to any pattern, may be applied in using the present method as illustrated in U.S.
Patent No. 3,927,716 to Burdyn et al. ey the term "pore volume" as used herein, is meant that volume of the portion of the formation underlying the well pattern employed, as described in grea-ter detail in the Burdyn et al. patent.
OIL-CONTAINING SUBSURFACE FORMATION
This invention is directed to a method of recovering oil from a viscous oil-containing subsurface formation. More particularly, this invention is directed to a hydrocarbon solvent recovery method for recovering oil from a subsurface formation which is penetrated by at least one injection well and one production well which extend from the surface of the earth and into the subsurface formation containing viscous hydrocarbons.
In U.S. Patent No. 4~293,035 of John L. Fitch, lssued October 6, 1981, there is disclosed a method of reca~ering viscous oil from 3 viscous oil-bearing subsurface formation wherein a solvent is injected into a high mobility channel formed in the bottom of the formation intermediate an injection well and a production well.
The solvent is injected until the ratio of produced oil to solvent becomes unfavorable and thereafter the injection of solvent is terminated and gas is injected into the high mobility channel to produce solvent and oil from the formation.
In U.S. Patent 3,838,738 there is described a method for recovering viscous petroleum from petroleum-containing formations by first establishing a fluid communication path low in the formationO A
heated fluid is then injected into the fluid communication path followed by injecting a volatile solvent such as carbon disulfide, benzene or toluene into the preheated flow path and continuing injecting the heating fluid and recovering fluids including petroleum from the production on well.
In U.S. Patent 3,500,917 there is disclosed a method for recovering crude oil from an oil-bearing formation having a water-saturated zone underlying the oil-saturated zone. A mixture of an aqueous fluid which has a density greater than the density of the crude oil and a solvent having a density less than the density of the crude oil are injected into the water-saturated zone and oil is produced ~rom the formation.
U.S. Patent 4,026,358 discloses a method for recovering heavy oil from a subterranean hydrocarbon-bearing formation traversed by at least one injection well and one production well wherein a slug of hydrocarbon solvent in amounts of 0.1 to about 20 percent o~ the formation pure volume and having a gas dissolved therein is injected into the ~ormation via the injection well. Thereafter, a thermal sink is created in the formation by in-situ combustion or by injecting steam. The wells are then shut in for a predetermined time to permit the formation to undergo a soak period, after which production is continued. Optionally, after the production period, the formation may be water flooded to recover additional oil from the formation.
This invention is directed to a method of recovering viscous oil from a viscous oil-containing formation that has no significant vertical permeability barrier in the portion of the formation to be tested and which is penetrated by at least one injection well and one production well. A fluid communication path is established through the lower portion of the subsurface formation intermediate the injection well and the production well, and a hydrocarbon solvent for the viscous oil having a viscosity not greater than 1/100 the viscosity of the oil contained in the formation under formation conditions and a specific gravity less than the oil contained in the formation, is injected via the injection well into this path and fluids including oil are recovered from the production well until the produced fluid contains an unfavorable ratio of oil to solvent. When this occurs, the production well is shut-in snd an additional quantity of hydrocarbon solvent, which is liquid under formation conditions, is injected into the formation via the injection well and through the fluid communication path, preferably until a total amount within the range of 0.05 to 0.30 pore volume has been injected. Thereafter, the injecticn well is shut-in along with the shut-in production well to permit the formation to undergo a soak period for a variable time, preferably for a period of time between 2 to 20 days per vertical thickness in feet of the viscous oil-containing formation. During this soak period, the light hydrocarbon solvent will tend to rise and the heavy oil will move F-1089 ~3 downward in a gravity-driven convection process forming a pattern of fingers. This fingering causes a more effective contact between the oil and solvent thus providing a greater volume of oil that is reduced in viscosity and which can be produced more readily. Thereafter, a driving fluid such as water is injected into the injection well to displace the mixture of oil and solvent toward the production well for recovery. Production is continued until the fluid including oil recovered from the production well contains an unfavorable ratio of oil to driving fluid.
The term "viscous oil~' is used herein to identify oil having relatively high viscosity and includes those oils referred to as tars.
Such viscous oils are also referred to as heavy oils. In general, the term viscous oil is used to include those heavy oils and tars such as are commonly found in formations referred to as heavy oil or tar sands that have viscosities that are great enough to severely restrict the production of the oils from the formations in which they are found.
The API gravity of such viscous oils is normally 20 API or less.
The accompanying drawing is a cross-sectional view illustrating a method according to one example of the invention of recovering oil from a subsurface oil-containing formation.
Referring to the drawing, a viscous oil bearing formation 10 that has no significant vertical p~ il;ty barriers is penetrated by an injection well 12 and a production well 14. The injection well 12 and production well 14 are perforated or fluid flow communication is otherwise established only adjacent the lower portion of the viscous oil-containing formation, and preferably only in the lower lû percent or less of the formation designated as 16 in the drawing. A fluid communication path 18 is established intel ~;ate the injection and production wells 12 and 14 through the lower portion of the viscous oil-containing formation 10. Thereafter, a hydrocarbon solvent having a specific gravity less than the specific gravity of the oil contained in the formation and having a viscosity not greater than 1/100 of the viscosity of the oil contained in the formation under formation conditions is injected via the injection well 12 through the fluid 7~33 communication path 18 and fluid including oil is recovered from the formation via production well 14. Solvent injection is continued until the fluid being recovered from the production well 14 comprises an unfavorable ratio of oil to solvent.
Thereafter, production well 14 is shut-in and an additional quantity of hydrocarbon solvent, which is liquid under formation conditions, is injected into the lower portion of the formation via the injection well 12 through the fluid communication path 18. The total amount of solvent injected is preferably within the range of 0.05 to 0~30 pore volume. Once this amount of solvent has been injected, the injection well 12 is shut-in along with the shut-in production well 14 and the formation is permitted to undergo a soak period for a variable time, preferably for a period of time between 2 to 2û days per vertical thickness in feet of the viscous oil-containing formation. It will be recognized by those skilled in the art of oil recovery that during this shut-in or soak period minor amounts of injection or production fluid, such as for the purpose of testing, may be done without significant detrimental effects on the process. Guring the soak period, the liquid hydro~arbon solvent being lighter than the oil contained in the viscous oil-~ontaining formation, that is, having a specific gravity less than the specific gravity of the oil contained in the formation and having a viscosity not greater than lJlûO of the viscosity of the oil contained in the formation under formation conditions, will tend to flow by gravity-driven convection upward into the oil containing formation and the neavy oil will flow by gravity-driven convection downward to form a hydrocarbon solvent-oil convection pattern as shown by the dashed lines 20 in the drawing. Furthermore, because of viscous instabilities, the rising hydrocarbon solvent and descending heavy oil form a pattern of fingers. This fingering is important in that the distribution, size and extension of these fingers will provide intimate contact between the solvent and the heavy oil allowing the two to mix more effectively, thus forming a greater volume of oil that is reduced in viscosity and which can be produced more readily. This relatively low viscosity mixture can be much more effectively displaced from the reservoir than F-1089 ~5~
the original heavy oil by flooding the formation with water or other suitable fluid, as is well known to those skilled in the art of petroleum engineering.
Once the soak period has been completed, a driving fluid is injected into the fluid communication path 18 via the injection well 12 and fluid including oil and hydrocarbon solvent is recovered from the production well 14. It is preferred that additional per~orations may be added to the injection well 12 or the production well 18, or both if desired, to establish fluid communication in both wells throu~hout the entire portion of the formation and thus obtain a more uniform displacement of the mobilized reservoir oils by the driving fluid. The driving fluid displaces both the oil and hydrocarbon solvent from the viscous oil-containing formation into the production well 14 and production is continued until the recovered Fluid contains an unfavorable ratio of oil to driving fluid. The driving fluid may be gaseous or liquid. For example, suitable gases include light aliphatic h~dlocarbu(,s having from one to four carbon atoms; carbon dioxide and nitr~gen may be used. However, aqueous fluids are partlcularly pre-ferred as the driv mg fluid, wqth water, brine and thickened aqueous 1uids all being suitable aque~us ~luids.
The fluid communication path 18 through the lower portion of the viscous oil-containing subsurface formation may be formed by injecting brine having a specific gravity greater than the specific gravity of the oil into the subsurface formation via the injection well 12 and through the perforations therein and into the oil-containing subsurface formation until the brine breaks through at the production well 14. In some formations brine may underlie the oil contained in the subsurface formation. In such cases, an oil-water contact will exist in the formation 10 and no additional brine need be injected into the formation to establish the fluid communication path 18. In such cases, it will be appreciated that the fluid communication path 18 is established by determining the existence of the oil-water contact and the brine-filled portion of the formation that underlies the oil 7~3;3 contained therein and communicates with the injection and the production well.
In the case of an oil-containing formation that is underlain by water and thus has an oil-water contact, the injection well is perforated and the perforation interval is provided adjacent the underlying water. Desirably, the upper perforations of this perforation interval are located about adjacent the oil-water contact though it could extend somewhat above this oil-water contact without seriously affecting the efficiency of the present recovery method. The production well is perforated and the perforation interval is provided adjacent the oil-water contact such that the lower perforation of this interval is located slightly above the oil-water contact. Again, in the case of a formation underlain by water, as it was with the formation that was not underlain by water, the perforation intervals that are provided in the injection and production wells desirably are no longer than about 10 percent of the total thickness of the vlscous oil-containing formation.
In the case of a formation underlain by brine which forms a fluid communication path between the injection and production well~s, the hydrocarbon solvent is selected to have a specific gravity less than that of the brine in addition to being less than that of the oil contained in the viscous oil-containing formation. The hydrocarbon solvent is in~ected via the injection well into this brine-filled fluid communication path and the process is continued in the same manner described above for the formation which is not underlain by water.
The hydrocarbon solvents used in the process of the invention should have a specific gravity less than that of the oil and less than that of the brine injected or naturally present in the formation and a visco~ity not greater than 1/100 the viscosity of the oil contained in the formation under formation conditions. It is also highly desirable that the hydrocarbon solvent remain liquid under the temperature and pressure conditions that exist in the subsurface viscous oil-containing formation and not cause solids such as asphaltenes to precipitate from the oil in amounts sufficient to seriously plug the pores of the formation. The preferred hydrocarbon solvent is a light crude oil.
Other examples of suitable hydrocarbon solvents include light oil condensates having an API gravity greater than 30 API degrees and partially refined tar which is generally known as syncrude. It may be desirable to include in the hydrocarbon solvent up to about 10 percent of aromatic material such as aromatic refinery stock to make the solvent compatible with the oil contained in the formations and to prevent the deposition of solid or gelatinous materials such as asphaltenes therefrom.
The viscous oil-containing subsurface formation to be treated by the present hydrocarbon solvent recovery method should be one that has no significant vertical permeab;lity barriers in that portion of the formation to be treated. This allows the solvent that is injected into the fluid communication path formed bet~leen the injection well and production well to flow upward into the formation by convection forces thus solllh;li7ing the oil and forming a solvent-oil mi~ture of reduced viscosity that can be more readily produced by a fluid drive process.
The method according to the invention is not restricted to the use in the field in which only two wells penetrate the formation. Any other number of wells, which may be arranged according to any pattern, may be applied in using the present method as illustrated in U.S.
Patent No. 3,927,716 to Burdyn et al. ey the term "pore volume" as used herein, is meant that volume of the portion of the formation underlying the well pattern employed, as described in grea-ter detail in the Burdyn et al. patent.
Claims (10)
1. A method of recovering viscous oil from a viscous oil-containing subsurface formation penetrated by at least one injection well and one production well comprising:
(a) establishing a fluid communication path extending between the injection well and the production well near the lower portion of said oil-containing formation;
(b) injecting a hydrocarbon solvent via said injection well into said fluid communication path, said solvent having a specific gravity less than the specific gravity of the oil contained in the formation and a viscosity not greater than 1/100 the viscosity of the oil contained in the formation under formation conditions and recovering fluids including oil and solvent from the fluid communication path via the production well until the fluid comprises an unfavorable ratio of oil to solvent;
(c) thereafter shutting-in said production well;
(d) continuing to inject a quantity of said hydrocarbon solvent into the fluid communication path via said injection well;
(e) shutting in said injection well along with the shut-in production well to permit said formation to undergo a soak period for a time sufficient for gravity-driven convection to substantially mix the solvent with the oil in the formation and thereby reduce its viscosity; and (f) thereafter injecting a driving fluid into the formation via said injection well and recovering fluids including oil from said formation via said production well until the fluid being recovered from the production well comprises an unfavorable ratio of produced oil to driving fluid.
(a) establishing a fluid communication path extending between the injection well and the production well near the lower portion of said oil-containing formation;
(b) injecting a hydrocarbon solvent via said injection well into said fluid communication path, said solvent having a specific gravity less than the specific gravity of the oil contained in the formation and a viscosity not greater than 1/100 the viscosity of the oil contained in the formation under formation conditions and recovering fluids including oil and solvent from the fluid communication path via the production well until the fluid comprises an unfavorable ratio of oil to solvent;
(c) thereafter shutting-in said production well;
(d) continuing to inject a quantity of said hydrocarbon solvent into the fluid communication path via said injection well;
(e) shutting in said injection well along with the shut-in production well to permit said formation to undergo a soak period for a time sufficient for gravity-driven convection to substantially mix the solvent with the oil in the formation and thereby reduce its viscosity; and (f) thereafter injecting a driving fluid into the formation via said injection well and recovering fluids including oil from said formation via said production well until the fluid being recovered from the production well comprises an unfavorable ratio of produced oil to driving fluid.
2. The method of Claim 1 wherein the total amount of solvent injected during steps (b) and (d) is between 0.05 and 0.30 pore volume and the soaking period during step (e) is for a period of time between 2 and 20 days per vertical thickness in feet of the oil-containing formation.
3. The method of Claim 1 wherein said fluid communication path is established by injecting a brine having a density greater than the density of said oil into the lower portion of said subsurface formation and continuing to inject said brine until breakthrough at said production well.
4. The method of Claim 1 comprising the additional step prior to step (f) of establishing fluid communication in the injection well and the production well substantially thoughout the full thickness of the oil-containing formation.
5. The method of Claim 1 wherein the driving fluid injected during step (f) is injected into the fluid communication path between the injection well and the production well.
6. A method of recovering viscous oil from a subsurface formation that contains a viscous oil portion and a mobile brine portion immediately therebelow, said formation having no significant permeability barrier therein, said formation being penetrated by at least one injection well and one production well, said injection well and production well being in fluid communication with the oil-water interface of the formation, comprising:
(a) injecting a hydrocarbon solvent into said injection well, said solvent having a viscosity not greater than 1/100 the viscosity of the oil contained in the formation under formation conditions, a specific gravity less than the oil contained in the formation, and a specific gravity less than said brine and recovering fluids including solvent and oil from the production well until the fluid being recovered comprises an unfavorable ratio of oil to solvent;
(b) thereafter shutting-in said production well;
(c) continuing to inject a quantity of said hydrocarbon solvent into the injection well;
(d) shutting in said injection well along with the shut-in production well to permit said formation to undergo a soak period for a time sufficient for gravity-driven convection to substantially mix the solvent with the oil in the formation and thereby reduce its viscosity; and (e) thereafter injecting a driving fluid into the injection well and recovering fluids including oil from said formation via said production well until the fluid being recovered from the production well comprises an unfavorable ratio of produced oil to driving fluid.
(a) injecting a hydrocarbon solvent into said injection well, said solvent having a viscosity not greater than 1/100 the viscosity of the oil contained in the formation under formation conditions, a specific gravity less than the oil contained in the formation, and a specific gravity less than said brine and recovering fluids including solvent and oil from the production well until the fluid being recovered comprises an unfavorable ratio of oil to solvent;
(b) thereafter shutting-in said production well;
(c) continuing to inject a quantity of said hydrocarbon solvent into the injection well;
(d) shutting in said injection well along with the shut-in production well to permit said formation to undergo a soak period for a time sufficient for gravity-driven convection to substantially mix the solvent with the oil in the formation and thereby reduce its viscosity; and (e) thereafter injecting a driving fluid into the injection well and recovering fluids including oil from said formation via said production well until the fluid being recovered from the production well comprises an unfavorable ratio of produced oil to driving fluid.
7. The method of Claim 6 wherein the total amount of solvent injected during steps (a) and (c) is between 0.05 and 0.30 pore volume and the soaking period during step (d) is for a period of time between 2 and 20 days per vertical thickness in feet of the oil-containing formation.
8. The method of claim 1 or claim 6 wherein the driving fluid is a gaseous material selected from the group consisting of carbon dioxide, nitrogen or aliphatic hydrocarbons having one to four carbon atoms.
9. The method of claim 1 or claim 6 wherein the driving fluid is water.
10. The method of claim 1 or claim 6 wherein said hydrocarbon solvent is selected from the group consisting of a light crude oil having an API gravity greater than 30 API degrees and a light crude oil product generally known as syncrude.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000419021A CA1194783A (en) | 1983-01-06 | 1983-01-06 | Method of recovering oil from a viscous oil- containing subsurface formation |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000419021A CA1194783A (en) | 1983-01-06 | 1983-01-06 | Method of recovering oil from a viscous oil- containing subsurface formation |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1194783A true CA1194783A (en) | 1985-10-08 |
Family
ID=4124273
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000419021A Expired CA1194783A (en) | 1983-01-06 | 1983-01-06 | Method of recovering oil from a viscous oil- containing subsurface formation |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1194783A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8985205B2 (en) | 2009-12-21 | 2015-03-24 | N-Solv Heavy Oil Corporation | Multi-step solvent extraction process for heavy oil reservoirs |
-
1983
- 1983-01-06 CA CA000419021A patent/CA1194783A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8985205B2 (en) | 2009-12-21 | 2015-03-24 | N-Solv Heavy Oil Corporation | Multi-step solvent extraction process for heavy oil reservoirs |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4385662A (en) | Method of cyclic solvent flooding to recover viscous oils | |
| US4510997A (en) | Solvent flooding to recover viscous oils | |
| US3822748A (en) | Petroleum recovery process | |
| US4884635A (en) | Enhanced oil recovery with a mixture of water and aromatic hydrocarbons | |
| US4489783A (en) | Viscous oil recovery method | |
| CA1225927A (en) | Cyclic solvent assisted steam injection process for recovery of viscous oil | |
| US4418752A (en) | Thermal oil recovery with solvent recirculation | |
| US5167280A (en) | Single horizontal well process for solvent/solute stimulation | |
| US4007785A (en) | Heated multiple solvent method for recovering viscous petroleum | |
| US3954141A (en) | Multiple solvent heavy oil recovery method | |
| DE60224793T2 (en) | METHOD FOR IN SITU RECOVERY FROM A TREATMENT INFORMATION AND MIXING ADDITION MADE ACCORDING TO THIS METHOD | |
| US4466485A (en) | Viscous oil recovery method | |
| US4098336A (en) | Oil recovery process utilizing air and superheated steam | |
| US4398602A (en) | Gravity assisted solvent flooding process | |
| US4166503A (en) | High vertical conformance steam drive oil recovery method | |
| US3913671A (en) | Recovery of petroleum from viscous petroleum containing formations including tar sand deposits | |
| US4293035A (en) | Solvent convection technique for recovering viscous petroleum | |
| CA1053573A (en) | Method for recovering viscous petroleum from unconsolidated mineral formations | |
| US4022277A (en) | In situ solvent fractionation of bitumens contained in tar sands | |
| CA2693942A1 (en) | Methods for producing oil and/or gas | |
| CA1174163A (en) | Recovery of oil from tilted reservoirs | |
| US3850245A (en) | Miscible displacement of petroleum | |
| US4503910A (en) | Viscous oil recovery method | |
| US4373585A (en) | Method of solvent flooding to recover viscous oils | |
| US3847224A (en) | Miscible displacement of petroleum |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEC | Expiry (correction) | ||
| MKEX | Expiry |