Abstract: A method of recovering hydrocarbons from subterranean reservoirs by the use of a viscous microemulsion form the single phase region of the ternary diagram of a microemulsion system that is optimal at the reservoir salinity is disclosed. The microemulsion is obtained by first determining the reservoir salinity and viscosity, then determining the oil molar volume that corresponds to a microemulsion having the reservoir viscosity, then determining the oil or mixture of oils that correspond both to the oil molar volume determined above and the reservoir salinity. The oil is then used to create a microemulsion within the single phase region of an optimal microemulsion.

Abstract: An oil recovery method is disclosed which uses a particular class of alkylaryl sulfonate surfactants. The surfactants are derived from an extracted aromatic feedstock consisting essentially of benzene, toluene, xylenes, and lesser amounts of ethylbenzene, trimethylbenzenes, and tetramethylbenzenes. The aromatic feedstock is then alkylated with linear .alpha.-olefins to favor second-carbon attachment, and sulfonated to result in surfactants having high oil solubilization parameters and whose phase behavior is substantially independent of temperature over 120.degree.-250.degree. Fahrenheit.

Abstract: A method for recovering oil from a subterranean formation is disclosed wherein a novel solution is injected into and driven through the formation. The solution contains an effective amount of surface-active agent having the general formulaR.sub.1 O(C.sub.3 H.sub.6 O,.sub.m (C.sub.2 H.sub.4 O).sub.n YXwhereinR.sub.1 is a linear or branched alkyl radical, an alkenyl radical, or an alkyl or alkenyl substituted benzene radical, the non-aromatic portion of the radical containing from about 6 to about 24 carbon atoms;m has an average value of between about 1 and about 10;n has an average value of between about 1 and about 10;Y is a hydrophilic group; andX is a cation, preferably monovalent.