Salinity tolerant surfactant oil recovery process

Claim 1

In a method of recovering petroleum from a subterranean, petroleum-containing, permeable formation said formation also containing water of known or determinable salinity greater than 5000 parts per million total dissolved solids, said formation being penetrated by at least one injection well and by at least one production well, both wells being in fluid communication with the petroleum formation, comprising injecting an aqueous, saline surfactant-containing fluid into the formation via the injection well to displace and drive petroleum toward the production well from which it is recovered to the surface of the earth, said surfactant fluid comprising an aqueous fluid whose salinity is about equal to the salinity of the formation water and having dissolved therein surfactants comprising a mixture of at least two organic sulfonate primary anionic surfactants and at least one solubilizing co-surfactant, wherein the improvement comprises: blending at least two anionic organic sulfonate surfactants at least one of which is predominantly water soluble and at least one which is at least partially oil soluble to form a blend which requires a minimum amount of solubilizing co-surfactant to achieve a condition of borderline solubility

Claim 14

A method of recovering petroleum from a subterranean, petroleum-containing permeable formation penetrated by at least two wells in fluid communication therewith, said formation containing water having a known or determinable salinity of at least 5000 parts per million total dissolved solids, comprising: introducing into the formation via one of said wells, an aqueous saline fluid having a salinity about equal to the salinity of the formation water, said surfactant fluid comprising a solubilizing co-surfactant and a blend of at least two organic sulfonates one of which is predominantly water soluble and one of which is at least partially oil soluble, the blend of two or more organic sulfonates being chosen from a group of at least two blends of at least three organic sulfonates having different average equivalent weights, the selected blend requiring less of the solubilizing co-surfactant than the other blends to achieve a condition of borderline solubility in the saline fluid.

Claim 15

A method of recovering petroleum from a subterranean, petroleum-containing permeable formation penetrated by at least two wells in fluid communication therewith, said formation containing water having a known or determinable salinity of at least 5000 parts per million total dissolved solids, comprising: introducing into the formation via one of said wells, an aqueous saline fluid having a salinity about equal to the salinity of the formation water, said surfactant fluid comprising a solubilizing co-surfactant and a blend of at least two organic sulfonates one of which is predominantly water soluble and one of which is at least partially oil soluble, the blend of two or more organic sulfonates being chosen from a group of at least two blends of at least three organic sulfonates having different average equivalent weights, the selected blend requiring less of the solubilizing co-surfactant than the other blends to achieve a condition of borderline solubility in the saline fluid.

Claim 20

A method of recovering petroleum from a subterranean, petroleum-containing permeable formation, said formation containing water of known or determinable salinity and divalent ion concentration, said formation being penetrated by at least one injection well and one production well, both wells in fluid communication with the formation, comprising: a. preparing a first series of at least three samples comprising a first blend of two organic sulfonates in different weight ratios, one of the organic sulfonates being at least partially water soluble and one other of the organic sulfonates being at least partially oil soluble, the organic sulfonates having average equivalent weights which differ by at least 50; b. determining the minimum weight ratio of a preselected solubilizing co-surfactant selected from the group consisting of ethoxylated alkyl or alkylaryl compounds, alkyl or alkylarylpolyethoxy sulfates alkyl or alkylarylpolyethoxyalkyl sulfonates and mixtures thereof, required to solubilize each sample of the first series of blends of organic sulfonates in an aqueous fluid having a salinity about equal to the salinity of the formation water; c. preparing a second series of at least three samples of two organic sulfonates in different weight ratios, one of the organic sulfonates being at least partly water soluble and one other of the organic sulfonates being at least partly oil soluble, the average equivalent weights of the organic sulfonates differing by at least 50, at least one of the organic sulfonates of the second series having an average equivalent weight which differs from the corresponding organic sulfonate in the first series by at least 25; d. determining the minimum weight ratio of the same solubilizng co-surfactant as used in step (b) required to solubilize each sample of the second series of blends of organic sulfonates in an aqueous fluid having about the same salinity as was used in step (b); e. determining which series of blends of organic sulfonates require the lesser weight ratio of solubilizing co-surfactant for solubility in aqueous fluid having about the same salinity as the formation water; f. determining the concentration and weight ratio of the series of blended organic sulfonates identified in step (e) when used with the minimum weight ratio of solubilizing co-surfactant required for solubility at the salinity of the formation water which result in optimum oil recovery; g. preparing an aqueous saline surfactant-containing fluid comprising the preselected solubilizing co-surfactant and the organic sulfonate blend identified in step (e) above in the concentration and weight ratio determined in step (f) above having a salinity about equal to the salinity of the formation water; h. injecting the aqueous saline surfactant-containing fluid of step (f) into the petroleum containing formation via the injection well to displace the formation petroleum toward the production well; and i. recovering petroleum displaced by the surfactant-containing fluid from the formation via the production well.

Claim 21

A method of recovering petroleum from a subterranean, petroleum-containing permeable formation, said formation containing water of known or determinable salinity and divalent ion concentration, said formation being penetrated by at least one injection well and one production well, both wells in fluid communication with the formation, comprising: a. preparing a first series of at least three samples comprising a first blend of two organic sulfonates in different weight ratios, one of the organic sulfonates being at least partially water soluble and one other of the organic sulfonates being at least partially oil soluble, the organic sulfonates having average equivalent weights which differ by at least 50; b. determining the minimum weight ratio of a preselected solubilizing co-surfactant selected from the group consisting of ethoxylated alkyl or alkylaryl compounds, alkyl or alkylarylpolyethoxy sulfates alkyl or alkylarylpolyethoxyalkyl sulfonates and mixtures thereof, required to solubilize each sample of the first series of blends of organic sulfonates in an aqueous fluid having a salinity about equal to the salinity of the formation water; c. preparing a second series of at least three samples of two organic sulfonates in different weight ratios, one of the organic sulfonates being at least partly water soluble and one other of the organic sulfonates being at least partly oil soluble, the average equivalent weights of the organic sulfonates differing by at least 50, at least one of the organic sulfonates of the second series having an average equivalent weight which differs from the corresponding organic sulfonate in the first series by at least 25; d. determining the minimum weight ratio of the same solubilizng co-surfactant as used in step (b) required to solubilize each sample of the second series of blends of organic sulfonates in an aqueous fluid having about the same salinity as was used in step (b); e. determining which series of blends of organic sulfonates require the lesser weight ratio of solubilizing co-surfactant for solubility in aqueous fluid having about the same salinity as the formation water; f. determining the concentration and weight ratio of the series of blended organic sulfonates identified in step (e) when used with the minimum weight ratio of solubilizing co-surfactant required for solubility at the salinity of the formation water which result in optimum oil recovery; g. preparing an aqueous saline surfactant-containing fluid comprising the preselected solubilizing co-surfactant and the organic sulfonate blend identified in step (e) above in the concentration and weight ratio determined in step (f) above having a salinity about equal to the salinity of the formation water; h. injecting the aqueous saline surfactant-containing fluid of step (f) into the petroleum containing formation via the injection well to displace the formation petroleum toward the production well; and i. recovering petroleum displaced by the surfactant-containing fluid from the formation via the production well.