CA1145248A - Oil recovery method utilizing a surfactant slug driven by water of a controlled salinity - Google Patents
Oil recovery method utilizing a surfactant slug driven by water of a controlled salinityInfo
- Publication number
- CA1145248A CA1145248A CA000368041A CA368041A CA1145248A CA 1145248 A CA1145248 A CA 1145248A CA 000368041 A CA000368041 A CA 000368041A CA 368041 A CA368041 A CA 368041A CA 1145248 A CA1145248 A CA 1145248A
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- Prior art keywords
- surfactant
- salinity
- water
- injection
- reservoir
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Abstract
OIL RECOVERY METHOD UTILIZING A SURFACTANT SLUG
DRIVEN BY WATER OF A CONTROLLED SALINITY
(D#74,785-F) ABSTRACT OF THE DISCLOSURE
The efficiency of a low tension surfactant flooding program is improved by first determining the upper and lower boundaries for the range of injected water salinities, that, when intermingled with the injected aqueous surfactant slug will enable the surfactant to resist partitioning into an oil and/or emulsion phase and thereby continue to operate with maximum effectiveness.
The water in the driving slug is formulated to fall within the specified salinity boundaries and is then injected at the appropriate time in the sequence of steps in the oil recovery operation.
-I-
DRIVEN BY WATER OF A CONTROLLED SALINITY
(D#74,785-F) ABSTRACT OF THE DISCLOSURE
The efficiency of a low tension surfactant flooding program is improved by first determining the upper and lower boundaries for the range of injected water salinities, that, when intermingled with the injected aqueous surfactant slug will enable the surfactant to resist partitioning into an oil and/or emulsion phase and thereby continue to operate with maximum effectiveness.
The water in the driving slug is formulated to fall within the specified salinity boundaries and is then injected at the appropriate time in the sequence of steps in the oil recovery operation.
-I-
Description
5~
BACKGROUND OF THE INVENTION
Field of the Invention This invention relates to a method for recovering petroleum from an underground petroleum reservoir wherein an injected surfactant containing fluid is driven by a quantity of water which has a predetermined salinity level designed to prevent partitioning of the surfactant into the oil and/or emulsion phase and thereby retainin~ maximum effectivness of the surfactant.
Description of the Prlor Art The crude oil which has accumulated in subter-ranean reservoirs is recovered or produced through one or more wells drilled into the reservoir. Initial production of the crude oil is accomplished by "primary recovery"
lS techniques wherein the natural forces present in the reservoir are utilized to produc:e the oil. However, upon depletion of these natural forces and the termination of primary recovery a large portion of the crude oil remains trapped within the reservoir. Also, many reservoirs lack sufficient natural forces to be produced by primary methods from the very beginning. Recognition of these facts has led to the development of many enhanced oil recovery techniques. Most of these techniques involve injection of at least one fluid into the reservoir to produce an addi-tional amount of the crude oil therefrom. Some of the morecommon methods are water flooding, steam flooding, miscible flooding, C02 flooding, polymer flooding, surfactant Elood-ing, caustic flooding and in situ combusion.
Water flooding, involves injection of water into the subterranean oil reservoir for the purpose ~.
of displacing the crude oil from the pore spaces of the reservoir rock towards the producing wells. It is the most economical and widely used of the oil recovery methods.
Nevertheless water does not displace oil with high effi-ciency because of the high interfacial tension between themand because of the resultant immiscible displacement of oil by water.
Surfactant flooding involves the addition of one or more surface active agents, usually referred to as "surfactants", to the water flood for the purpose of minimiæing the water flooding problems mentioned above.
This has heen an area of active interest in the art of enhanced oil recovery methods for many years. For example, in 1941 U. S. Patent No. 2,233,381 disclosed the use of polyglycolether as a surfactant which increases the capil-lary displacement efficiency of an aqueous flood. U. S.
Patent No. 3,302,713 discloses the use of petroleum sulfon-ates as effective surfactants in oil recovery operations.
Other surfactants proposed for use in oil recovery processes include alkyl sulfates, alkylaryl sulfates, ethoxylated alkyl or aryl sulfates, alkyl sulfonates, alkylaryl sulfon-ates and quaternary ammonium salts.
While the above surfactants may be effective under ideal conditions, there are problems concerned with the use of each in most petroleum reservoirs. Some of the most serious problems arise from the effects of salinity extremes in the fluids which contact the surfactant within the reservoir. Such salinity extremes can cause surfactant precipitation and/or surfactant partitioning out of the agueous phase and into the oil or emulsion phases. This results in an increase in retention of the surfactant within the reservoir matrices and fluids with a resultant loss of efficiency for the surfactant flooding process.
SUMMARY OF THE INVENTION
This invention relates to an enhanced oil recovery process useful in the recovery of oil from subterranean petroleum reservoirs wherein a surfactant containing fluid is injected which is followed by an aqueous driving slug of controlled salinity. The salinity of this aqueous drivin~
slug is designed to fall within upper and 16wer salinity limits which the surfactant=containing fluid can tolerate without precipitation or formation of emulsions or multiple pha~es.
BRIEF DESCRIPTION OF THE FIGURES OF THE DRAWING
Fig. 1 shows the effect of drive water salinity on oil recovery efficiency in a ~urfactant flood for vari-ous pore volumes of injected fluid, and Fig. 2 shows the effect of varying the surfactant partition coefficient on oil recovery efficiency using drive water with a salinity of 40,000 ppm.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The usual seguence of operations for a surfactant floodins tec~nigue involving surfactants which are effectiveonly within a narrow band of salinities i~ a first step comprising the injection, as necessary, of a preflush fluid designed to condition a reservoir for ~he surfac~ant followea by injections of aqueous surfactant and pol~mer solutions which are the~ driven through the rese.rvoir by further injection of water. The preflush fluid is injected to enable the aqueous surfactant solution to operate with maximum effectiveness. The preflush fluid usually consists of a low salinity or fresh water often with sacrificial agents added thereto. The injection of the lower salinity , ,, ;,;
or fresh watex serves to reduce the salinity of the forma-tion fluids ~hat the following surfactant slug will encount-er. The ~acrificial agents are designed to occupy potential precipitation sites within the formation matrix which would S attract and cause the following surfactant to precip -3a-: i ~ ?, itate were it not for the presence of the sacrificial agent. ~any chemicals have been proposed in the art as sacrificial agents chemically modified lignosulfonates appear to be especially useful in this regard.
The sacrificial agents can be readily selected by one of ordinary skill in the art. In some cases the preflush fluid may not be necessary where the formation fluids are already at a salinity level which would not require further modification to allow the surfactant to operate with maximum effectiveness.
The surfactant contemplated for use in the method of this invention can be any of the commonly used oil field surfactants and especially those which are intolerant of high salinity reservoir environments. The surfactant is injected in the aqueous phase. The surfactant-containing fluid comprises the surfactant, fresh or briny water and, optionally, additives such as ~acrificial agents and polymers. The concentration of the surfactant used will vary generally depending upon the particular surfactant as well as the water salinity, water hardness and the chemical composition of the reservoir rocks. It is highly preferred that the optimum response at various concentrations be measured under conditions simulating those which will be present in the reservoir in the concen-tration corresponding to the optimum surfactant performance.Generally, the concen-tration of the surfactant will be from about 0.OS to ~bout 10.0% by weight. Although the precise formulation is readily determinable by one with ordinary skill in the art, the volume of the surfactant-containing fluid can vary from about 2 to about 50 pore volume percent. It is anticipated that the injected volume of the surfactant containing fluid would be optimized at the most economically efficient level.
Injection of the surfactant-containing fluid is followed by injection of an aqueous solution of a hydro-philic polymer in order to obtain an effective level of conformance control during the injection process. Generally from about 5 to about 50 pore volume percent of an aqueous solution containing from about 0.01 to about l.0 percent by wei~h~ of a hydrophilic polymer such as polyacrylamide or polysaccharide is used.
Although the injection of the high viscosity polymer slug provides some measure of conformance control, i almost invariably the subsequent injection of the much lower viscosity drive water will cause this drive water to break through the polymer into the surfactant-containing fluid slug. Heretofore this effect has been neglected.
However, we have discovered that:, unless the salinity of the drive water is carefully controlled, partitioning of the surfactant into undesirable oil or emulsion phases will - occur upon contact with drive water of undesirable salinities.
To this end we propose an improvement upon the above surfactant flooding oil recovery process wherein the drive water is of a carefully controlled salinity level designed to prevent this phenomenon of surfactant partitioning out of the aqueous phase.
Surfactant partitioning out of the aqueous phase can occur when the surfactant encounters fluids which are either of too high or too low salinity. The surfactant-containing fluid should therefore be tested by mixing zl~
therewith several samples of the drive water at differentsalinity levels. In this manner the upper and lowex salinity bounds for an effective drive water formulation which will not cause partitioning of the surfactant out of the water phase can be determined. A drive water is then selected that falls within these salinty boundaries and is injected. Following the injection of the polymer slug, injection of this controlled salinity drive water can either be continuous until the termination of the surfactant flooding process or take the form of a discreet slug following the injection of the polymer slug then being followed by a drive water of unspecified salinity. Which-ever method is used the result must be the same, namely, that any drive water which breaks through the polymer slug into the surfactant-containing slug will be at this con-trolled salinity level.
Reference is now made to the following examples which serve to illustrate the i~vention more fully. The invention should, however, not be deemed as limited to these examples.
E X A M P L E
Experiments were conducted using a computer program which simulates the enhanced oil recovery process as it takes place within the reservoir. The process of this invention was tested within the confines of one stream tube 330 feet long which is a realistic simulation of the condition~ that exist along one fluid path within the reservoir. The following reservoir parameters were e~ployed.
L~
Porosity .138 Absolute permeability 754 darcies Reservoir thickness 2.7 feet Initial Oil saturation .702 Irreducable water saturation .25 Irreducable oil saturation .25 Viscosity of the water .967 cp Viscosity o the oil 3.60 cp The parameters of the simulated low tension 10 water flood were as follows:
Surfactant slug si7.e .243 pore volumes Injected polymer slug size .210 pore volumes Surfactant concentration 16,640 ppm Polymer concentration 674 ppm 15 Final low tension irreducable oil saturation .05 Constant injection rate into the stream tube 7.0 barrels per day The upper and lower limits for salt concentration expressed as concentration of the chlorine ion were 12,100 and 3,030 ppm respectively. Two different simulated low tension water floods were then run, one with a drive water salinity measured as a concentration of the chlorine ion of 4,000 ppm and the other with the drive water salinity again measured as a concentration of the chlorine ion of 40,000 ppm. The 4,000 ppm concentration corresponds to a drive water salinity that is compatible with the surfactant in as much as it causes no decrease in oil recovery effi-~ ~52~3 ciency. The 40,000 ppm salinity drive water corresponds toan incompatible salinity level which causes a marked decrease oil recovery efficiency. A surfactant partition coefficient of 25 was utilized for both simulations. This coefficient is defined as the ratio of the surfactant concentration in the oil phase to that in the aqueous phase. Although this example demonstrates the effects of one drive water salinity which exceeds the upper salinity boundary a similar undesirable oil recovery would result from the use of a drive water with a salinity below the lower salinity boundary.
The results of these computer simulations are reported in Fig. 1 and show that the drive water salinity is indeed a critical factor. Thle drive water at the 4,000 ppm salinity level which is within the acceptable salinity range reaches a recovery efficiency level of . 80 where the drive water at the 40,000 ppm salinity which is above acceptable salinty level does not exceed a recovery effi-ciency of more than .45.
E X A M P L E II
The experiments in this example utilize the same computer simulation model as in Example I for the case of 40,000 ppm drive water salinity but vary the partition coefficien~ of the surfactant instead of the drive water salinity as in Example I. The parameters for the reservoir and water flood were the same as in Example I.
~ ~ 5 These simulations were restricted to one layer and on~
stream tube and used partition coefficients of O.O, 5.0, 25.0 and 50.0, where the partition coefficient again represents the oil phase to the surfactant concentration in the water phase. Hence, a value o O for the partition coefficient corresponds to a surfactant that will be found only in the water phase.
The resulting oil recovery efficiency curves are plotted in Fig. 2. Several conclusions can be drawn from this figure. First, increased surfactant partitioning into the oil phase, as expressed by increasing higher partitionin~ coefficients, results in a time delay in the oil recovery response. This increased residence time within the stream tube upon partitioning into the oil phase is apparently caused by a lower mobility for the surfactant when it is in the oil phase. Second, the oil recovery efficiency drops markedly as the partition coef-ficient increases. Third, the ultimate oil recovery efficiency is higher at a low level for the partition coefficient ~han for the zero partition coefficient. This indicates ~hat a small degree of partitioning of the sur~
factant into the oil phase is in fact desirable.
BACKGROUND OF THE INVENTION
Field of the Invention This invention relates to a method for recovering petroleum from an underground petroleum reservoir wherein an injected surfactant containing fluid is driven by a quantity of water which has a predetermined salinity level designed to prevent partitioning of the surfactant into the oil and/or emulsion phase and thereby retainin~ maximum effectivness of the surfactant.
Description of the Prlor Art The crude oil which has accumulated in subter-ranean reservoirs is recovered or produced through one or more wells drilled into the reservoir. Initial production of the crude oil is accomplished by "primary recovery"
lS techniques wherein the natural forces present in the reservoir are utilized to produc:e the oil. However, upon depletion of these natural forces and the termination of primary recovery a large portion of the crude oil remains trapped within the reservoir. Also, many reservoirs lack sufficient natural forces to be produced by primary methods from the very beginning. Recognition of these facts has led to the development of many enhanced oil recovery techniques. Most of these techniques involve injection of at least one fluid into the reservoir to produce an addi-tional amount of the crude oil therefrom. Some of the morecommon methods are water flooding, steam flooding, miscible flooding, C02 flooding, polymer flooding, surfactant Elood-ing, caustic flooding and in situ combusion.
Water flooding, involves injection of water into the subterranean oil reservoir for the purpose ~.
of displacing the crude oil from the pore spaces of the reservoir rock towards the producing wells. It is the most economical and widely used of the oil recovery methods.
Nevertheless water does not displace oil with high effi-ciency because of the high interfacial tension between themand because of the resultant immiscible displacement of oil by water.
Surfactant flooding involves the addition of one or more surface active agents, usually referred to as "surfactants", to the water flood for the purpose of minimiæing the water flooding problems mentioned above.
This has heen an area of active interest in the art of enhanced oil recovery methods for many years. For example, in 1941 U. S. Patent No. 2,233,381 disclosed the use of polyglycolether as a surfactant which increases the capil-lary displacement efficiency of an aqueous flood. U. S.
Patent No. 3,302,713 discloses the use of petroleum sulfon-ates as effective surfactants in oil recovery operations.
Other surfactants proposed for use in oil recovery processes include alkyl sulfates, alkylaryl sulfates, ethoxylated alkyl or aryl sulfates, alkyl sulfonates, alkylaryl sulfon-ates and quaternary ammonium salts.
While the above surfactants may be effective under ideal conditions, there are problems concerned with the use of each in most petroleum reservoirs. Some of the most serious problems arise from the effects of salinity extremes in the fluids which contact the surfactant within the reservoir. Such salinity extremes can cause surfactant precipitation and/or surfactant partitioning out of the agueous phase and into the oil or emulsion phases. This results in an increase in retention of the surfactant within the reservoir matrices and fluids with a resultant loss of efficiency for the surfactant flooding process.
SUMMARY OF THE INVENTION
This invention relates to an enhanced oil recovery process useful in the recovery of oil from subterranean petroleum reservoirs wherein a surfactant containing fluid is injected which is followed by an aqueous driving slug of controlled salinity. The salinity of this aqueous drivin~
slug is designed to fall within upper and 16wer salinity limits which the surfactant=containing fluid can tolerate without precipitation or formation of emulsions or multiple pha~es.
BRIEF DESCRIPTION OF THE FIGURES OF THE DRAWING
Fig. 1 shows the effect of drive water salinity on oil recovery efficiency in a ~urfactant flood for vari-ous pore volumes of injected fluid, and Fig. 2 shows the effect of varying the surfactant partition coefficient on oil recovery efficiency using drive water with a salinity of 40,000 ppm.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The usual seguence of operations for a surfactant floodins tec~nigue involving surfactants which are effectiveonly within a narrow band of salinities i~ a first step comprising the injection, as necessary, of a preflush fluid designed to condition a reservoir for ~he surfac~ant followea by injections of aqueous surfactant and pol~mer solutions which are the~ driven through the rese.rvoir by further injection of water. The preflush fluid is injected to enable the aqueous surfactant solution to operate with maximum effectiveness. The preflush fluid usually consists of a low salinity or fresh water often with sacrificial agents added thereto. The injection of the lower salinity , ,, ;,;
or fresh watex serves to reduce the salinity of the forma-tion fluids ~hat the following surfactant slug will encount-er. The ~acrificial agents are designed to occupy potential precipitation sites within the formation matrix which would S attract and cause the following surfactant to precip -3a-: i ~ ?, itate were it not for the presence of the sacrificial agent. ~any chemicals have been proposed in the art as sacrificial agents chemically modified lignosulfonates appear to be especially useful in this regard.
The sacrificial agents can be readily selected by one of ordinary skill in the art. In some cases the preflush fluid may not be necessary where the formation fluids are already at a salinity level which would not require further modification to allow the surfactant to operate with maximum effectiveness.
The surfactant contemplated for use in the method of this invention can be any of the commonly used oil field surfactants and especially those which are intolerant of high salinity reservoir environments. The surfactant is injected in the aqueous phase. The surfactant-containing fluid comprises the surfactant, fresh or briny water and, optionally, additives such as ~acrificial agents and polymers. The concentration of the surfactant used will vary generally depending upon the particular surfactant as well as the water salinity, water hardness and the chemical composition of the reservoir rocks. It is highly preferred that the optimum response at various concentrations be measured under conditions simulating those which will be present in the reservoir in the concen-tration corresponding to the optimum surfactant performance.Generally, the concen-tration of the surfactant will be from about 0.OS to ~bout 10.0% by weight. Although the precise formulation is readily determinable by one with ordinary skill in the art, the volume of the surfactant-containing fluid can vary from about 2 to about 50 pore volume percent. It is anticipated that the injected volume of the surfactant containing fluid would be optimized at the most economically efficient level.
Injection of the surfactant-containing fluid is followed by injection of an aqueous solution of a hydro-philic polymer in order to obtain an effective level of conformance control during the injection process. Generally from about 5 to about 50 pore volume percent of an aqueous solution containing from about 0.01 to about l.0 percent by wei~h~ of a hydrophilic polymer such as polyacrylamide or polysaccharide is used.
Although the injection of the high viscosity polymer slug provides some measure of conformance control, i almost invariably the subsequent injection of the much lower viscosity drive water will cause this drive water to break through the polymer into the surfactant-containing fluid slug. Heretofore this effect has been neglected.
However, we have discovered that:, unless the salinity of the drive water is carefully controlled, partitioning of the surfactant into undesirable oil or emulsion phases will - occur upon contact with drive water of undesirable salinities.
To this end we propose an improvement upon the above surfactant flooding oil recovery process wherein the drive water is of a carefully controlled salinity level designed to prevent this phenomenon of surfactant partitioning out of the aqueous phase.
Surfactant partitioning out of the aqueous phase can occur when the surfactant encounters fluids which are either of too high or too low salinity. The surfactant-containing fluid should therefore be tested by mixing zl~
therewith several samples of the drive water at differentsalinity levels. In this manner the upper and lowex salinity bounds for an effective drive water formulation which will not cause partitioning of the surfactant out of the water phase can be determined. A drive water is then selected that falls within these salinty boundaries and is injected. Following the injection of the polymer slug, injection of this controlled salinity drive water can either be continuous until the termination of the surfactant flooding process or take the form of a discreet slug following the injection of the polymer slug then being followed by a drive water of unspecified salinity. Which-ever method is used the result must be the same, namely, that any drive water which breaks through the polymer slug into the surfactant-containing slug will be at this con-trolled salinity level.
Reference is now made to the following examples which serve to illustrate the i~vention more fully. The invention should, however, not be deemed as limited to these examples.
E X A M P L E
Experiments were conducted using a computer program which simulates the enhanced oil recovery process as it takes place within the reservoir. The process of this invention was tested within the confines of one stream tube 330 feet long which is a realistic simulation of the condition~ that exist along one fluid path within the reservoir. The following reservoir parameters were e~ployed.
L~
Porosity .138 Absolute permeability 754 darcies Reservoir thickness 2.7 feet Initial Oil saturation .702 Irreducable water saturation .25 Irreducable oil saturation .25 Viscosity of the water .967 cp Viscosity o the oil 3.60 cp The parameters of the simulated low tension 10 water flood were as follows:
Surfactant slug si7.e .243 pore volumes Injected polymer slug size .210 pore volumes Surfactant concentration 16,640 ppm Polymer concentration 674 ppm 15 Final low tension irreducable oil saturation .05 Constant injection rate into the stream tube 7.0 barrels per day The upper and lower limits for salt concentration expressed as concentration of the chlorine ion were 12,100 and 3,030 ppm respectively. Two different simulated low tension water floods were then run, one with a drive water salinity measured as a concentration of the chlorine ion of 4,000 ppm and the other with the drive water salinity again measured as a concentration of the chlorine ion of 40,000 ppm. The 4,000 ppm concentration corresponds to a drive water salinity that is compatible with the surfactant in as much as it causes no decrease in oil recovery effi-~ ~52~3 ciency. The 40,000 ppm salinity drive water corresponds toan incompatible salinity level which causes a marked decrease oil recovery efficiency. A surfactant partition coefficient of 25 was utilized for both simulations. This coefficient is defined as the ratio of the surfactant concentration in the oil phase to that in the aqueous phase. Although this example demonstrates the effects of one drive water salinity which exceeds the upper salinity boundary a similar undesirable oil recovery would result from the use of a drive water with a salinity below the lower salinity boundary.
The results of these computer simulations are reported in Fig. 1 and show that the drive water salinity is indeed a critical factor. Thle drive water at the 4,000 ppm salinity level which is within the acceptable salinity range reaches a recovery efficiency level of . 80 where the drive water at the 40,000 ppm salinity which is above acceptable salinty level does not exceed a recovery effi-ciency of more than .45.
E X A M P L E II
The experiments in this example utilize the same computer simulation model as in Example I for the case of 40,000 ppm drive water salinity but vary the partition coefficien~ of the surfactant instead of the drive water salinity as in Example I. The parameters for the reservoir and water flood were the same as in Example I.
~ ~ 5 These simulations were restricted to one layer and on~
stream tube and used partition coefficients of O.O, 5.0, 25.0 and 50.0, where the partition coefficient again represents the oil phase to the surfactant concentration in the water phase. Hence, a value o O for the partition coefficient corresponds to a surfactant that will be found only in the water phase.
The resulting oil recovery efficiency curves are plotted in Fig. 2. Several conclusions can be drawn from this figure. First, increased surfactant partitioning into the oil phase, as expressed by increasing higher partitionin~ coefficients, results in a time delay in the oil recovery response. This increased residence time within the stream tube upon partitioning into the oil phase is apparently caused by a lower mobility for the surfactant when it is in the oil phase. Second, the oil recovery efficiency drops markedly as the partition coef-ficient increases. Third, the ultimate oil recovery efficiency is higher at a low level for the partition coefficient ~han for the zero partition coefficient. This indicates ~hat a small degree of partitioning of the sur~
factant into the oil phase is in fact desirable.
Claims (7)
1. In a process for recovering petroleum from a subterranean reservoir wherein the reservoir is penetrated by at least one injection well and at least one production well, said wells being in fluid communication with each other, which comprises injecting a surfactant-containing fluid into the reservoir through said injection well, further injecting a driving agent and recovering petroleum from said production well, the improvement comprising:
a. determining the upper and lower salinity levels that the surfactant in the surfactant-containing fluid can tolerate and remain able to recover the petroleum efficiently, and, b. preparing and injecting the driving agent at a salinity level that is between said upper and lower salinity levels, wherein the driving agent contains as a first increment a quantity off a fluid comprising water and an amount of a hydrophilic polymer sufficient to raise the viscosity of the increment to an effective level, the volume of the increment ranging from about 0.1 to about 1.0 pore volumes of the reservoir.
a. determining the upper and lower salinity levels that the surfactant in the surfactant-containing fluid can tolerate and remain able to recover the petroleum efficiently, and, b. preparing and injecting the driving agent at a salinity level that is between said upper and lower salinity levels, wherein the driving agent contains as a first increment a quantity off a fluid comprising water and an amount of a hydrophilic polymer sufficient to raise the viscosity of the increment to an effective level, the volume of the increment ranging from about 0.1 to about 1.0 pore volumes of the reservoir.
2. The process of claim 1 wherein the injection of the driving agent is followed by the injection of water of an unspecified salinity.
3. The method of claim 2 wherein the injected volume of the driving agent is sufficient to prevent break-through of the injected water of unspecified salinity into the injected surfactant-containing fluid.
4. In a process for recovering petroleum from a subterranean reservoir wherein the reservoir is penetrated by at least one injection well and at least one production well, said wells being in fluid communication with each other, which comprises injecting a surfactant-containing fluid into the reservoir through said injection well, then injecting a fluid comprising water and a quantity of a hydrophilic polymer sufficient to raise the viscosity of the fluid to an effective level, further injecting a driving agent comprising water and recovering petroleum from said production well, the improvement comprising:
a. controlling the salinity of the driving agent so as to prevent the precipitation of the surfactant out of the surfactant-containing fluid and the irreversible phase.
a. controlling the salinity of the driving agent so as to prevent the precipitation of the surfactant out of the surfactant-containing fluid and the irreversible phase.
5. The process of claim 4 wherein the process further comprises injecting a formation conditioning fluid prior to the injection of the surfactant-containing fluid.
6. The process of claim 4 wherein the injection of the driving agent is followed by the injection of water of an unspecified salinity.
7. The process of claim 6 wherein the injected volume of the driving agent is sufficient to prevent breakthrough of the injected water of unspecified salinity into the injected surfactant-containing fluid.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000368041A CA1145248A (en) | 1981-01-07 | 1981-01-07 | Oil recovery method utilizing a surfactant slug driven by water of a controlled salinity |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000368041A CA1145248A (en) | 1981-01-07 | 1981-01-07 | Oil recovery method utilizing a surfactant slug driven by water of a controlled salinity |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1145248A true CA1145248A (en) | 1983-04-26 |
Family
ID=4118853
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000368041A Expired CA1145248A (en) | 1981-01-07 | 1981-01-07 | Oil recovery method utilizing a surfactant slug driven by water of a controlled salinity |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1145248A (en) |
-
1981
- 1981-01-07 CA CA000368041A patent/CA1145248A/en not_active Expired
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