High conformance oil recovery process

Claim 1

A method of recovering petroleum from a subterranean, petroleum-containing formation, the temperature of said formation being from 80° F. to 300° F. said formation containing water whose salinity is from 20,000 to 250,000 parts per million total dissolved solids, said formation containing at least two distinct petroleum-containing strata or layers, the permeability of at least one of said strata being at least 50 percent greater than the permeability of the other stratum, said formation being penetrated by at least one injection well and by at least one production well, both wells being in fluid communication with at least two of said formation strata, comprising (a) injecting a first aqueous oil-displacing fluid into the formation via the injection well, said fluid passing through at least one of the more permeable strata of said formation and displacing oil therein toward the production well, from which it is recovered to the surface of the earth; (b) after said first aqueous oil displacing fluid has passed substantially through at least one of said more permeable strata to the production well, discontinuing injecting said fluid and injecting into said stratum an aqueous emulsifying fluid containing an emulsifying surfactant combination comprising (1) an organic sulfonate anionic surfactant selected from the group consisting of water soluble sodium, potassium or ammonium salts of alkyl sulfonates having from 9 to 25 carbon atoms, alkylaryl sulfonates having from 8 to 15 carbon atoms in the alkyl chain, or petroleum sulfonate whose median equivalent weight is from 325 to 475, (2) an aliphatic polyalkoxyalkylene sulfonate or alkylarylpolyalkoxyalkylene sulfonate having the following formula: RO(R'O).sub.n R"SO.sub.3 M wherein R is an aliphatic, preferably an alkyl, linear or branched, having from 9 to 25 carbon atoms, or an alkylaryl group selected from the group consisting of benzene, toluene, and xylene having attached thereto at least one alkyl group, linear or branched, having from 8 to 15 carbon atoms; R' is ethylene or a mixture of ethylene and higher molecular weight alkylene with relatively more ethylene than higher molecular weight alkylene; n is a number including fractional numbers, from 2 to 10; R" is ethylene, propylene, hydroxy propylene or butylene, and M is a monovalent cation selected from the group consisting of sodium, potassium, lithium and ammonium; (c) thereafter injecting a second oil displacing fluid into the formation and recovering petroleum displaced by the fluid from the formation via the producing well.

Claim 2

A method of recovering petroleum from a subterranean, petroleum-containing formation, the temperature of said formation being from 80° F. to 300° F. said formation containing water whose salinity is from 20,000 to 250,000 parts per million total dissolved solids, said formation containing at least two distinct petroleum-containing strata or layers, the permeability of at least one of said strata being at least 50 percent greater than the permeability of the other stratum, said formation being penetrated by at least one injection well and by at least one production well, both wells being in fluid communication with at least two of said formation strata, comprising (a) injecting a first aqueous oil-displacing fluid into the formation via the injection well, said fluid passing through at least one of the more permeable strata of said formation and displacing oil therein toward the production well, from which it is recovered to the surface of the earth; (b) after said first aqueous oil displacing fluid has passed substantially through at least one of said more permeable strata to the production well, discontinuing injecting said fluid and injecting into said stratum an aqueous emulsifying fluid containing an emulsifying surfactant combination comprising (1) an organic sulfonate anionic surfactant selected from the group consisting of water soluble sodium, potassium or ammonium salts of alkyl sulfonates having from 9 to 25 carbon atoms, alkylaryl sulfonates having from 8 to 15 carbon atoms in the alkyl chain, or petroleum sulfonate whose median equivalent weight is from 325 to 475, (2) an aliphatic polyalkoxyalkylene sulfonate or alkylarylpolyalkoxyalkylene sulfonate having the following formula: RO(R'O).sub.n R"SO.sub.3 M wherein R is an aliphatic, preferably an alkyl, linear or branched, having from 9 to 25 carbon atoms, or an alkylaryl group selected from the group consisting of benzene, toluene, and xylene having attached thereto at least one alkyl group, linear or branched, having from 8 to 15 carbon atoms; R' is ethylene or a mixture of ethylene and higher molecular weight alkylene with relatively more ethylene than higher molecular weight alkylene; n is a number including fractional numbers, from 2 to 10; R" is ethylene, propylene, hydroxy propylene or butylene, and M is a monovalent cation selected from the group consisting of sodium, potassium, lithium and ammonium; (c) thereafter injecting a second oil displacing fluid into the formation and recovering petroleum displaced by the fluid from the formation via the producing well.