Oil recovery by surfactant flooding - using petroleum sulphonate with equiv. wt. lower than that giving minimum interfacial tension

摘要

Oil recovery from subterranean formations contg. water with a total salinity of 2000-20,000 ppm and a divalent-ion (Ca2+ and Mg2+) concn. of 0-1000 ppm is carried out by surfactant flooding. The flooding medium is an aq. saline soln. with a total salinity of 2000-20,000 ppm and a divalent-ion concn. of 0-2000 (pref. 0-1000)ppm contg. a petroleum sulphonate whose average equivalent weight (AEW) is 2-20 (pref. 5-15)% less or 20-100 (pref. 30-70) units less than the AEW which produces the minimum interfacial tension between the petroleum and water in the formation. The recovery efficiency is better than that achieved using a petroleum sulphonate sample giving minimum interfacial tension (e.g. a 77-55% increase in recovery can be achieved for a given surfactant concn.).