Abstract: A method for determining the average equivalent weight of hydrocarbon sulfonates and the optimal salinity and unique salinity of surfactant systems containing such hydrocarbon sulfonates is based on the discovery that the average equivalent weights of hydrocarbon sulfonates vary inversely and linearly as the optimal salinities and unique salinities of surfactant systems containing such hydrocarbon sulfonates vary. Methods of preparing surfactant systems for the displacement of oil from subterranean reservoirs and for the displacement of oil from subterranean reservoirs, based on the above-mentioned relationships, are also disclosed.

Abstract: The optimum aqueous surfactant system for forming an efficient multiphase microemulsion system in situ is determined by comparing the behavior of oil from the formation to be flooded with the behavior of simple hydrocarbons in an equilibration test with a standard surfactant system. Thereafter, salt concentration, equivalent weight of the sulfonate and/or alcohol solubility is varied based on criterion disclosed herein to arrive at the optimum system for recovery of the specific oil in question.