Interfacial Performance Evaluation of Combined Surfactants in Different Reservoirs

Abstract In recent years, Qinghai Oilfield which is situated in the northeastern part of the Tibetan Plateau has entered the “high water cut” stage after years of water flooding development. The overall stable production development situation of the main oil reservoirs is grim. It is very necessary to develop the research and development of chemical enhanced oil recovery (EOR) technologies such as surfactant flooding after water flooding. In accordance with the reservoir features of the Qinghai Oilfield, which have extremely high formation water salinity and high concentrations of calcium and magnesium ions, combined surfactant named QZBH with high resistance to high levels of calcium and magnesium, good solubility, and good compatibility was obtained through more than 200 groups of compound evaluation experiments. This surfactant has demonstrated good oil-increasing results during the processes of profile control and oil displacement, well washing, and huff and puff in Qinghai Oilfield, but its interfacial performance evaluation has not yet formed a standard detection and evaluation method, and the optimal oil displacement concentration has lacked the basis for selection. Taking the interfacial tension detection standard method suitable for Qinghai Oilfield as the experimental evaluation basis, the optimal concentration of surfactants for different oil reservoirs was determined by measuring and evaluating the interfacial tension value of combined surfactant in different oil reservoirs: the best concentration for GS-z and GS-s, YS, and five other oil reservoirs is 0.3%; for NY and WN oil reservoirs, it is 0.8%; the interfacial performance of YJ and QT oil reservoirs is poor, and the next step is to comprehensively consider other performance evaluation indicators of surfactants as well as the geological features of oil reservoirs, and continue to carry out indoor research and evaluation of surfactant ratios and concentrations suitable for target oil reservoirs. The above experimental outcomes can furnish a scientific foundation for the subsequent expansion of the application scale of QZBH combined surfactant, improve the applicability of different processes, and achieve the objective of reducing costs and increasing efficiency.