Abstract: A method for recovering oil from a subterranean formation is disclosed wherein an aqueous surfactant solution is injected into the formation to reduce the mobility of gas in a gas-flooding process. The gas may include hydrocarbon gas, inert gas, carbon dioxide, and steam, or mixtures thereof. The surfactant is represented by the general formula ##STR1## where R is a linear or branched chain alkyl group with n carbon atoms wherein n ranges from about 6 to about 50, except that if the gas is steam n ranges from about 9 to about 50;Ar is a mononuclear or fused ring dinuclear aryl group;Z is an ionic group consisting of --SO.sub.3.sup.- M.sup.+ or --R'SO.sub.3.sup.- M.sup.+ wherein M.sup.+ is a cation and R' is a linear or branched chain alkyl group of from one to about six carbon atoms;x ranges from 0 to about 20; andy ranges from 3 to about 100.

Abstract: A method for recovering oil from a subterranean formation is disclosed wherein an aqueous surfactant solution is injected into the formation to reduce the mobility of gas in a gas-flooding process. The gas may include hydrocarbon gas, inert gas, carbon dioxide, and steam. The surfactant is represented by the general formula ##STR1## where R is a linear or branched chain alkyl group with n carbon atoms wherein n ranges from 0 to about 18, except that if the gas is steam n ranges from about 9 to about 30;x ranges from 0 to about 20 and y ranges from 0 to about 20, provided x+y does not exceed about 20;R' is a linear or branched chain alkyl group with m carbon atoms wherein m ranges from 0 to 4, except that if the gas is steam m ranges from 1 to 4, with the proviso that the sum of x+y+m is at least one; andeach M.sup.+ is a cation.

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: Additional amounts of crude oil are recovered from a subterranean formation by flooding with a translucent emulsion comprising an upper- or middle-phase microemulsion as an external phase and a polymer-containing brine solution as an internal phase. The translucent emulsion tends to coalesce into its component phases under conditions of no shear, but is stabilized by low shears such as those imposed on fluids flowing through a subterranean formation.

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.

Abstract: A method of enhanced oil recovery is disclosed wherein an upper-phase or a middle-phase microemulsion and an immiscible aqueous phase are simultaneously injected into a subterranean formation. The viscosities of the injected phases are adjusted so that the aqueous phase/microemulsion viscosity ratio approximates the reservoir brine/oil viscosity ratio. The injection rates of the injected phases are such that similar oil, microemulsion and aqueous phase velocities are achieved in the reservoir. Oil is displaced to a production well and recovered.