The Laboratory Experiment Of Surfactant-polymer System In Enhancing Producible Oil Index

ASP is a kind of mature flooding technique in EOR. It cooperates alkali, surfactant and polymer to flood oil reserves. It can produce a ultra low interfacial tension to oil with very low concentration of surfactant, and improve displacement efficiency largely; on the other hand, as a result of the addition of polymer, the system has a high viscidity, and it can get an advantageous mobility ratio, consequently it enhance producible oil index largely. ASP experiment practice in Daqing oil reserves had gotten preferable effect, which enhanced producible oil index by 20%.But during the practical use of ASP some questions follow. Among them the most severe effect on oil and formation is that alkali can lower formation permeability because it can scrap formation clay and make them move and can form alkali scale, such as carbonate scale and aluminosilicate scale, after it reacts with formation fluid and rock. Alkali can lower largely viscoelasticity of flooding system .As a result sweeping volume is lowered because of viscidity fingering. So if alkali is eliminated we will get surfactant-polymer system that has low interfacial tension and get rid of scale effect on viscoelasticity of flooding system. Furthermore surfactant-polymer system is easier to get and generalize and has good viscoelasticity. Even if it cannot produce ultra low interfacial tension, its last producible oil index may equal that of APS. After experimental study, it has been concluded that surfactant-polymer system can enhance producible oil index by 20%.Surfactant can lower interfacial tension between oil and water and alter rocky wettability, so it will be used extensively. To surfactant-polymer system, in order to improve the oil recovery efficiently, a kind of better surfactant need be found. This is the most important factor before selecting surfactant-polymer system. According to the result of repeated experiment, compound surfactant EP-1 is selected as surfactant in surfactant-polymer system .In the paper, according to the request of interfacial tension attaining to 10"2 mN/m in surfactant-polymer system, EP-1 system had been researched. After study of interfacial tension, surfactant EP-1 and formation of surfactant-polymer system were confirmed. In the same time, analysis method had been formed and absorbing curve of EP-1 surfactant-polymer system had been determined. In the end, laboratory experiment of this surfactant-polymer system had been done and it could improve the oil recovery efficiency.