Surfactant oil recovery process usable in high temperature formations containing water having high concentrations of polyvalent ions

In a method for recovering petroleum from a subterranean, petroleum-containing formation penetrated by at least one injection well and at least one production well, said formation containing water having polyvalent ions dissolved therein in a concentration of from about 200 to about 14,000 parts per million and at a pH from 5 to about 9, said recovery method being of the type wherein an aqueous fluid is injected into the formation via the injection well, and oil displaced by the injected fluid is recovered from the formation via the production well, wherein the improvement comprises injecting into the formation an aqueous three component surfactant solution comprising:

• a. an anionic surfactant with an average molecular weight not to exceed about 360 selected from the group consisting of water-soluble salts of alkyl sulfonates having from 5 to 25 carbon atoms, and water soluble salts of alkylaryl sulfonates wherein the alkyl chains have from 5 to 25 carbon atoms;
• b. a phosphate ester surfactant with an average molecular weight not to exceed about 1000 having the following formula ##EQU5## wherein R is alkylphenyl or an alkyl radical having from 12 to 24 carbon atoms, m is an integer between 1 and 20, x and y are 1 or 2 and the sum of x and y is 3, and M is a monovalent cation;
• and
• c. a sulfonated betaine having the following structure:
• ##EQU6## wherein R is an alkyl group having from 12 to 24 carbon atoms and n is an integer from 1 to 5.