Method of increasing enhanced oil recovery by using a novel low sulfonate phase in the polymer slug

摘要

This invention relates to a process for enhanced recovery of hydrocarbons from a subterranean hydrocarbon-bearing formation penetrated by an injection well and a production well wherein, before injection, the surfactant fluid is separated into two phases by the addition of small amounts of polymer and the portion having the higher sulfonate content is used as the surfactant slug. As an improvement we disclose the step of adding the phase of surfactant fluid with the lower sulfonate content to the polymer slug which is used to drive the surfactant fluid to further increase recovery.