Surfactant flooding oil recovery process

Claim 1

In a method of recovering petroleum from a subterranean permeable, petroleum-containing formation, said formation containing water having a salinity of at least 20,000 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 formation, comprising injecting an aqueous, surfactant-containing fluid into the formation via the injection well to displace petroleum toward the production well, from which it is recovered to the surface of the earth, said surfactant fluid containing an alkylpolyalkoxyalkylene sulfonate or alkylarylpolyalkoxyalkylene sulfonate surfactant having the following formula: RO(R'O).sub.n R"SO.sub.3.sup.- M.sup.+ wherein R is an alkyl group having from 9 to 25 carbon atoms, or an alkylaryl group, containing at least one alkyl substituent containing from 9 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, R" is ethylene, propylene, hydroxy propylene or butylene, n is a number from 2 to 10 and M + is sodium, potassium, lithium or ammonium, wherein said improvement for increasing said phase stability and injectability of a surfactant fluid, and improving its low surface tension oil displacement effectiveness, which comprises: shearing the surfactant fluid at the surface at a shear rate of at least 150 reciprocal seconds for a period of time of at least 0.1 minutes and sufficient to render the surfactant fluid less turbid prior to injecting it into the formation via the injection well.