Surfactant oil recovery process

Claim 2

In a method of recovering petroleum from a porous, subterranean, petroleum-containing formation penetrated by at least one injection well and at least one production well, wherein a surfactant solution .Iadd.effective within determinable concentration ranges of hardness and salinity .Iaddend.is injected into the formation .Iadd.via the injection well and petroleum is recovered from the formation via the production well, .Iaddend.the improvement for increasing the efficiency of the surfactant which comprises: a. determining the .Iadd.optimum performance .Iaddend.range of salinity and polyvalent ion concentrations for .[.which.]. the surfactant .[.produces the minimum interfacial tension between water and formation petroleum.].; and b. injecting an aqueous .Iadd.preflush .Iaddend.solution of a hydrophilic polymeric viscosity increasing material, said aqueous preflush solution having a salinity and polyvalent ion concentrations within the optimum performance range as determined in step (a), into the formation prior to injecting the surfactant solution, to displace the formation water through the formation ahead of the surfactant solution.

Claim 3

A method as recited in claim 1 wherein the hydrophilic polymeric viscosity increasing material is selected from the group consisting of polyacrylamide, polysaccharide, methyl cellulose, carboxy methyl cellulose, polyvinyl aromatic sulfonate and polyethylene oxide.

Claim 4

A method as recited in claim 2 wherein the hydrophilic polymeric material is polyacrylamide.

Claim 5

A method as recited in claim 2 wherein the hydrophilic polymeric material is polysaccharide.

Claim 6

A method as recited in claim 2 wherein the hydrophilic polymeric material is methyl cellulose.

Claim 7

A method as recited in claim 2 wherein the hydrophilic polymeric material is polyvinyl aromatic sulfonate.

Claim 8

A method as recited in claim 2 wherein the hydrophilic polymeric material is polyethylene oxide.

Claim 9

A method as recited in claim 1 wherein the concentration of hydrophilic polymeric material in the aqueous preflush solution is from about 25 to about 2,000 parts per million.

Claim 10

A method as recited in claim 1 wherein the concentration of polymeric material in the aqueous preflush solution is from about 200 to about 500 parts per million.

Claim 11

A method as recited in claim 1 wherein from about 0.2 to about 0.5 pore volumes of the aqueous preflush solution is injected into the formation.

Claim 12

A method as recited in claim 1 wherein from about 0.1 to about 0.3 pore volumes of the aqueous preflush solution is injected into the formation.

Claim 13

A method as recited in claim 1 wherein the concentration of hydrophilic polymer in the aqueous preflush solution is decreased with time as the aqueous preflush solution is injected into the formation.

Claim 14

A method as recited in claim 1 wherein an isolation slug of from about 0.05 to about 0.5 pore volumes of water having a salinity less than the salinity of the formation water is injected into the formation after the injection of the aqueous preflush solution and before the injection of the surfactant solution.

Claim 15

A method as recited in claim 1 wherein the salinity of the aqueous preflush solution is from 0 to about 20,000 parts per million.

Claim 16

A method as recited in claim 1 wherein the concentration of polyvalent ions in the preflush is from about 0 to about 18,000 parts per million.

Claim 17

A method as recited in claim 1 wherein the optimum salinity and polyvalent ion concentration for minimum interfacial tension production is determined by capillary displacement tests.

Claim 18

A method as recited in claim 1 comprising the additional step of determining the pH at which the surfactant produces the minimum interfacial tension and adjusting the pH of the aqueous preflush solution to a value essentially equal to the determined value.

Claim 19

A method as recited in claim 17 wherein the pH of the surfactant solution is essentially equal to the pH of the preflush solution.

Claim 20

A method as recited in claim 1 wherein the salinity and hardness of surfactant solution is essentially equal to the preflush solution.

Claim 21

A method as recited in claim 1 wherein the aqueous solution of a hydrophilic polymeric viscosity increasing material additionally contains sacrificial agents to lower adsorption of surfactant from the surfactant solution injected after the aqueous solution of hydrophilic polymeric material.

Claim 22

A method as recited in claim 20 wherein the sacrificial agents are added to lower adsorption of polymer. .Iadd. 22. In a method of recovering petroleum from a porous, permeable subterranean, petroleum-containing formation penetrated by at least one injection well and at least one production well in fluid communication with the formation, wherein a surfactant solution effective within determinable concentration ranges of hardness and salinity is injected into the formation via the injection well and petroleum is recovered from the formation via the production well, the improvement for increasing the efficiency of the surfactant which comprises: a. determining the range of salinity and polyvalent ion concentrations for which the surfactant produces the minimum interfacial tension between water and formation petroleum; and b. injecting an aqueous preflush solution of a hydrophilic, polymeric viscosity-increasing material, said aqueous preflush solution having a salinity and polyvalent ion concentration within the range for which the surfactant produces the minimum interfacial tension between water and formation petroleum as determined in step (a), into the formation prior to injecting the surfactant solution, to displace the formation water through the formation ahead of the surfactant solution. .Iaddend..Iadd. 23. In a method of recovering petroleum from a porous, permeable subterranean, petroleum-containing formation penetrated by at least one injection well and at least one production well in fluid communication with the formation wherein a surfactant-containing fluid is injected into the formation via the injection well and petroleum is recovered from the formation via the production well, the surfactant-containing fluid having a known range of salinity and polyvalent ion concentrations for effective performance, the improvement for increasing the efficiency of the surfactant which comprises: injecting an aqueous preflush solution of a hydrophilic, polymeric viscosity-increasing material, said aqueous preflush solution having a salinity and polyvalent ion concentration within said known effective performance range for the surfactant fluid into the formation prior to injecting the surfactant fluid, to displace the formation water through the formation ahead of the surfactant fluid. .Iaddend..Iadd. 24. A method as recited in claim 23 wherein the surfactant fluid comprises petroleum sulfonate and the optimum performance range of salinity is less than 20,000 parts per million total dissolved solids. .Iaddend..Iadd. 25. In a method for recovering petroleum through a production well from a porous, petroliferous formation by injecting through an injection well a surfactant solution of controlled hardness and salinity within determinable controllable effective concentration values of hardness and salinity for at least partial displacement of petroleum to a production well, the improvement for increasing the effectiveness of said surfactant for displacing petroleum which comprises: injecting into said formation ahead of said surfactant solution an aqueous hydrophilic polymer-containing, preflush solution of said effective hardness and salinity values. .Iaddend.