A Study On Medium-phase Flooding System With Low Concentration Surfactant

At present,my country's high water-cut oilfields have entered the middle and late stage of development.Various chemical flooding technologies have been applied to oilfield production and have achieved good EOR effects.However,the current oilfield production still faces problems such as formation scaling,equipment corrosion and limited range of enhanced oil recovery.Therefore,the development of an efficient alkali-free flooding system is of great significance for oilfield production.The paper mainly carried out the research on the formulation of alkali-free medium phase flooding system.First,the parameters such as Krafft point,critical micelle concentration,solubility,light transmittance and interfacial tension of a single surfactant were tested,and then the compound components of anionic and anionic nonionic surfactants were determined,and the compound surface was carried out.Solubility evaluation and interfacial tension testing of active agent systems under high salinity conditions.The phase state test was carried out with the selected compound surfactants,and the effects of the type and proportion of compound surfactants,surfactant concentration,auxiliary alcohol content,oil-water ratio and oil phase components on the volume of the middle phase were analyzed.,and test the microemulsion's microstructure and phase state characterization parameters,and finally evaluate the oil displacement effect and analyze the oil displacement mechanism of the optimal medium-phase microemulsion system.The research results show that the anionic and nonionic surfactants with EO chain have good salt resistance and water solubility,and the combination of anionic and nonionic surfactants and anionic surfactants improves the high salinity of single anionic surfactants.The problems of poor solubility and low interfacial activity under conditions;the optimal surfactant compound system formula is RH-1 and petroleum sulfonate in the ratio of 1:4;the salt width ?S of the mid-phase microemulsion is 2.0%,and the maximum The optimum salinity S* is 1.2%,and the particle size range is between 80 nm and 200 nm.The microstructure of the mid-phase microemulsion includes two structures,the mid-phase microemulsion and the bicontinuous phase microemulsion.The results of the oil displacement evaluation experiment show that the chemical flooding recovery rate of the optimal mid-phase microemulsion system can be increased by 35%-40% after water flooding,and the system has the characteristics of significantly reducing the oil-water interfacial tension,seepage resistance and water content.