Studies on foam flooding for saline reservoirs after polymer flooding

Abstract

Abstract Multiple betaine surfactant PSDA (penta sodium N, N′, N′′-dodecyl diethylene triamine pentaacetic acid) is a kind of Zwitterionic Gemini surfactants with three dodecyls, five carboxylic acid groups and three quaternary ammonium. It has higher surface activities such lower cmc, lower γ cmc , lower IFT and better foaming properties than single chain surfactants, so, as foaming agent, it is used in foam flooding to displace oil in harsh reservoirs. Systematic experiments of foam flooding after water flooding had been performed for saline reservoirs. The foaming ability, stability and FCI (foam composite index) were the key factors to ensure high performance of oil recovery. The foam flooding formula was optimized by good performance of foaming ability, stability and FCI . The co-injection of foam was the most effective mode and the alternative injection of gas and solution was the poorest. The gas liquid ratio could also affect the flooding efficiencies greatly. The optimized gas liquid ratio was proposed as 4:1 for co-injection mode at the reservoirs condition. Results of single cores flooding experiments indicated that the resistance coefficient of the foam flooding was very high and the residual resistance coefficient was very low. Results of dual cores flooding experiments indicated that foam flooding with polymer could contribute 11–20% OOIP (original oil in place) recovery and had excellent profile control ability. Results of pilot test showed recovery oil of foam flooding was very considerable.