Research On Surfactant Flooding Characteristics In Ultra-Low Permeability Reservoirs

The development of low permeability reservoir is the main basis of oilfield production areas.The development of low permeability reservoirs generally means the surfactant flooding.Therefore,the research on how to use the surfactant to improve recovery factor of low permeability reservoirs more effectively is of great significance to the further development of low permeability reservoir.In this paper,through the macroscopic displacement experiment,which indicates the nuclear magnetic resonance analysis test,the analysis of surfactant flooding to improve oil recovery of low permeability reservoirs is implemented.Furthermore,the summary of the regularity and mechanism of the surfactant flooding oil displacement with the characteristics of low permeability reservoirs is made.The main achievements and understanding are as follows:(1)Under the condition of different concentrations with the same oil-water interfacial tension of surfactant system,the oil-water interface tension surfactant system brings different salinity and emulsification effect.Conclusion: 1.With the increase of salinity,the interfacial tension of oil and water reduces gradually.2.With the loss of the oil-water interfacial tension,the emulsification effect becomes weak gradually.3.In low interfacial tension of oil and water environment,emulsification is poor.(2)Using nuclear magnetic resonance technology,the author studies the similar permeability and wettability of low permeability cores in different structures of different pore throats and the effects of water flooding of different wettability cores.Then,the author observes the core recovery rate and the change of residual oil distribution after the injection of the surfactant solution.The results shows that the situation that wet core residual oil is after water flooding mainly exists in the small pores.The predictive form of an oil drop is theresidual oil.After water flooding oil wets core,the oil mainly exists in the form of membrane.Injected surfactant can significantly reduce the residual amount of residual oil,which mainly includes reducing interfacial tension of oil displacement mechanism,emulsified oils and etc.(3)Through macroscopic displacement experiments,besides its interfacial tension and emulsification,the other factors affecting surfactant oil displacement efficiency are core wettability,surfactant injection rate and core permeability.