Surfactant flooding secondary oil recovery - with surfactant comprising mixt. of petroleum sulphonates of specified average equivalent wt. distribution

摘要

A process for the secondary recovery of oil from subterranean promotions by surfactant flooding is claimed, the injected fluid being an aq. saline (=20000 ppm total dissolved solids) fluid contg. (a) a surfactant (I) consisting of petroleum sulphonates of specified average equivalent weights, and (b) a solubilising co-surfactant (II) selected from ethoxylated alkanols, ethoxylated alkylphenols, alkyl(aryl) polyethoxy sulphates and/or alkyl(aryl) polyalkoxyalkyl sulphonates. The specified pref. equivalent weight distribution of (I) optimises the surfactant flood formulations and enables accurate predictability of the enhanced recoveries.