Injectivity of crude oil and petroleum sulfonate slugs by the addition of an alkylbenzene sulfonate

Claim 1

A process for inhibiting the formation of insoluble precipitates in a crude oil sulfonation product wherein said crude oil sulfonation product is a component of a microemulsion that is to be injected into a subterranean, oil-bearing formation to recover oil therefrom, the process comprising the steps of: (a) mixing said crude oil sulfonation product, a hydrocarbon, water, and a cosurfactant to form said microemulsion; (b) filtering said microemulsion through a diatomaceous earth filter medium; and thereafter (c) adding an alkylbenzene sulfonate to said microemulsion at a concentration such that about 1 to about 40 weight percent of the resulting sulfonate groups in said microemulsion is attributable to said alkylbenzene sulfonate and the remaining weight percent of said sulfonate groups is attributable to said crude oil sulfonation product, and wherein said alkylbenzene sulfonate is defined by the formula: ##STR2## wherein R 1 and R 2 are alkyl groups containing about 10 to about 20 carbon atoms each and M is a monovalent cation; and (d) blending said microemulsion for a time sufficient to obtain uniform dispersion of said alkylbenzene sulfonate in said microemulsion, which substantially inhibits the formation of the insoluble precipitates therein.