Study On Surfactant For Heavy Oil Chemical Flooding

Chemical flooding is a potential method for enhancing oil recovery in heavy oil reservoirs.A key technology of chemical flooding is the construction of oil flooding system.The interfacial tension is an important indicator of chemical flooding system.But recent studies have found that systems with ultra-low interfacial tension have a large difference in oil displacement effect.Therefore,it is necessary to deeply study the relationship between interfacial tension,emulsification,wettability,oil washing ability and oil displacement efficiency.In this paper,aiming at Shengli Gudong heavy oil,three ultra-low interfacial tension systems were constructed,alkanolamide（6501）and alcohol ether carboxylate（SS233）were compounded in a ratio of 1:1,oleic acid amide propyl carboxybetaine（OAB）and alcohol ether carboxylate（SS233）were compounded in a ratio of 1:1,oleic acid amidopropyl hydroxysultaine（OHSB）and alcohol ether carboxylate（SS233）were compounded in a ratio of1:1.The interfacial tension between systems and Gudong heavy oil could reach 10^-3 m N·m^-1at 50℃.The emulsification,wettability,oil washing ability and oil displacement performance of these systems were further evaluated.Emulsification experiments showed that OAB/SS233（1:1）had the best emulsification effect for heavy oil,followed by 6501/SS233（1:1）,and the emulsification effect of OHSB/SS233（1:1）were the worst.The wettability experiments showed that 6501/SS233（1:1）increased the hydrophilicity of the slide,and OAB/SS233（1:1）changed the slide from hydrophilic to lipophilic.Oil washing experiments showed that the oil washing rates of three flooding systems were 50.67%,27.67%,and 45.22%.The results were related to the ability of the system to change the wettability.Sand-packing pipe displacement experiments and micro-displacement experiments showed that 6501/SS233（1:1）had the largest increase in recovery factor and the best oil displacement effect.In summary,the oil-displacing system with low interfacial tension and wettability remaining hydrophilic or weakly hydrophilic had the best oil washing ability and the highest oil-displacing effect.The oil washing ability of surfactants was directly related to the oil displacement effect.The higher the oil washing rate,the better the oil displacement effect of the system.The research results had guiding significance for the selection and evaluation of heavy oil chemical flooding system.