Emulsion oil recovery process usable in high temperature, high salinity formations

Claim 1

A method for recovering petroleum from a subterranean, permeable, petroleum-containing formation penetrated by at least one injection well and by at least one spaced-apart production well, both wells being in fluid communication with the formation, the temperature of the formation being from about 70° F. to about 300° F., said formation containing water having a salinity from 30,000 to 220,000 parts per million total dissolved solids, comprising: (1) injecting into the formation via the injection well a phase-stable surfactant-containig emulsion comprising a continuous, saline, aqueous phase and a dispersed hydrocarbon phase, the surfactant comprising: (a) from 0.05 to 10.0 percent by weight of a water soluble alkylpolyalkoxyalkylene sulfonate or alkylarylpolyalkoxyalkylene sulfonate having the following formula: RO(R'O).sub.x R"SO.sub.3 -M.sup.+ wherein R is an alkyl or alkylaryl group, linear or branched having from 8 to 24 carbon atoms in the alkyl chain, R' is ethylene or a mixture of ethylene and propylene having relatively more ethylene than propylene, x is a number from 1 to 20, R" is ethylene, propylene, hydroxypropylene or butylene, and M + is a monovalent cation; and (b) from 0.1 to 5.0 percent by weight of a low HLB, water insoluble nonionic surfactant having the following formula: R'''O(CH.sub.2 CH.sub.2 O).sub.y H wherein R''' has the same meaning as R and y is a number from 1 to 10; (c) said aqueous phase having a salinity from about 45 to 95percent of the formation water salinity; (2) thereafter injecting brine into the formation to displace the emulsion through the formation, the salinity of the brine being initially as great as the salinity of the aqueous phase of the emulsion and is decreased to a salinity value less than the salinity of the aqueous phase of the emulsion during the time period during which the brine is injected, said emulsion and brine displacing petroleum through the formation to the production well; and (3) recovering petroleum displaced by the emulsion and brine from the formation via the production well.

Claim 2

A method for recovering petroleum from a subterranean, permeable, petroleum-containing formation penetrated by at least one injection well and by at least one spaced-apart production well, both wells being in fluid communication with the formation, the temperature of the formation being from about 70° F. to about 300° F., said formation containing water having a salinity from 30,000 to 220,000 parts per million total dissolved solids, comprising: (1) injecting into the formation via the injection well a phase-stable surfactant-containig emulsion comprising a continuous, saline, aqueous phase and a dispersed hydrocarbon phase, the surfactant comprising: (a) from 0.05 to 10.0 percent by weight of a water soluble alkylpolyalkoxyalkylene sulfonate or alkylarylpolyalkoxyalkylene sulfonate having the following formula: RO(R'O).sub.x R"SO.sub.3 -M.sup.+ wherein R is an alkyl or alkylaryl group, linear or branched having from 8 to 24 carbon atoms in the alkyl chain, R' is ethylene or a mixture of ethylene and propylene having relatively more ethylene than propylene, x is a number from 1 to 20, R" is ethylene, propylene, hydroxypropylene or butylene, and M + is a monovalent cation; and (b) from 0.1 to 5.0 percent by weight of a low HLB, water insoluble nonionic surfactant having the following formula: R'''O(CH.sub.2 CH.sub.2 O).sub.y H wherein R''' has the same meaning as R and y is a number from 1 to 10; (c) said aqueous phase having a salinity from about 45 to 95percent of the formation water salinity; (2) thereafter injecting brine into the formation to displace the emulsion through the formation, the salinity of the brine being initially as great as the salinity of the aqueous phase of the emulsion and is decreased to a salinity value less than the salinity of the aqueous phase of the emulsion during the time period during which the brine is injected, said emulsion and brine displacing petroleum through the formation to the production well; and (3) recovering petroleum displaced by the emulsion and brine from the formation via the production well.