Consideration of Application Possibility of Biosurfactant and Alkaline-surfactant-polymer (B-ASP) with Ultra-low Crude Oil/Brine Interfacial Tension for Enhancement of Oil Recovery

With the increase in global energy demand and decrease in crude oil reserves, the technology for the enhancement of oil recovery is becoming increasingly important. Even after primary and secondary oil recovery, 60-70 % of the crude oil remains in oil reservoirs1),2). Chemical flooding technologies, including surfactant flooding3),4), polymer flooding5),6), surfactant-polymer flooding7),8), and alkaline-surfactant-polymer (ASP) flooding9),10), have been employed in different oil fields over the last few decades. Among these, ASP flooding is one of the leading technologies for tertiary oil recovery from declining oil reservoirs11),12), and has been successfully applied in several oilfields, including the Daqing, Shengli, and Xinjiang oilfields in China, with a remarkable increase of more than 20 % in oil recovery from water-flooded oil reservoirs with high water content. The most important mechanism of ASP flooding for enhancing oil recovery includes two closely correlated aspects: reduction in oil/brine interfacial tension (IFT) to an ultra-low level (≤ 103 mN/m), and improvement in the swept efficiency of flooding fluids in oil reservoirs13)~15). Evidently, a key factor for enhancing oil recovery is the decrease in oil/brine IFT to an ultra-low level (103 mN/m) at low surfactant dosage, and thus at low cost. In ASP flooding, the surfactant, i.e., petroleum sulfonate (NPS), is widely used owing to its high oil/water interfacial activity16)~18). However, to some extent, its industrial application is limited by a number of constraints. Commercial NPS is usually a mixture of sulfonates, unsulfonated oil, inorganic salts, and water19). The performances of sulfonates themselves vary significantly with the raw materials from which they are produced as well as the unpredictable production of polysulfonates20). In field applications, chromatographic [Regular Paper]