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

An aqueous surfactant-containing fluid for use in flooding subterranean formations which contain petroleum and water having dissolved therein from 200 to 14,000 parts per million divalent ions comprising calcium, magnesium and mixtures thereof, said formation having a temperature from about 125.degree. F to about 225.degree. F, comprising:

• a. from about 0.05 to about 5.0 percent by weight of an anionic surfactant with an average molecular weight not to exceed about 360 having one of the following two formulas:
• (R-X) Y
• wherein R is an alkyl radical, linear or branched, having from 8 to 14 carbon atoms, X is a sulfonate radical, and Y is sodium, potassium or ammonium, or ##STR6## wherein R, X and Y have the same meaning as above;
• b. from about 0.05 to about 5.0 percent by weight of a phosphate ester surfactant with an average molecular weight not to exceed about 1000 having the following formula:
• ##STR7## 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 R' is hydrogen, sodium, potassium or ammonium;
• c. from about 0.05 to about 5.0 percent by weight of a sulfonated betaine having the following structure:
• ##STR8## wherein R is an alkyl group having from 12 to 24 carbon atoms and n is an integer from 1 to 5 inclusive;
• and
• d. from about 200 to about 1400 parts per million divalent ions selected from the group consisting of calcium, magnesium and mixtures thereof.