Oil recovery by surfactant waterflooding

Abstract

Process for the recovery of oil from a subterranean oil reservoir involving injection into the reservoir of a substantially oil-free aqueous liquid containing a surfactant having a nonionic polyalkylene oxide hydrophilic group and an anionic sulfonate hydrophilic group molecularly linked to a common lipophilic base. The invention is applicable to reservoirs in which the connate waters have relatively high concentrations of divalent ions and in situations in which the water available for injection purposes contains relatively high amounts of divalent ions. Specifically disclosed surfactants include aliphatic aryl polyalkoxyol sulfonates in which the polyalkoxyol group contains at least three alkylene oxide units and is derived from ethylene oxide or propylene oxide or mixtures thereof. The aliphatic groups may be substituted directly on the aryl nucleus or indirectly as through an intermediate succinimido group.