Study On The Mechanism Of Enhanced Oil Recovery By Microemulsion Flooding In Low Permeability Reservoirs

This paper using sodium dodecyl sulfate,lauryl betaine,twain-20 as surfactant,n-butyl alcohol as a surfactant,different system of microemulsion system was prepared,and measuring the interfacial tension,viscosity,particle size distribution curve and stability parameters.With dodecyl betaine mixture microemulsion physical simulation experiments,in daqing oilfield is low permeability core as experimental object,carries on the determination of start-up pressure gradient and the relative permeability curve,lithography glass model of remaining oil research,microemulsion oil displacement experiment and core microscopic anatomy experiment,microemulsion were analyzed from different angles to improve recovery mechanism.Microemulsion of surfactants can be adsorbed on the surface of rock,greatly reduce the interfacial tension of solid-liquid,reduced the filtrational resistance of boundary layer fluid flow,in the tiny pore fluid in smaller displacement under pressure differential adhesion can be overcome and participate in the flow.At the same time,the ionic surfactants can be dissociated from a certain amount of charge,the charge can be adsorbed on the surface of the boundary layer of fluid,compression diffusion electric double layer,which reduces the boundary layer thickness,increasing the actual flow of pore area.Microemulsion system can be greatly reduced,therefore,the core of the start-up pressure gradient,reduce the resistance in the process of seepage.Low oil-water interfacial tension of oil droplets easy deformation,weakened the additional resistance produced by the jamin effect,make the oil phase relative permeability increased significantly,and reduce the residual oil saturation.Microemulsion droplets of remaining oil and membrane residual oil displacement effect is best,and for the blind end of remaining oil displacement effect is the worst.And pore throat radius ratio is the main factors which influence the displacement effect of microemulsion.Microemulsion can reduce oil-water interfacial tension and start-up pressure gradient,the improvement of oil flow rate,thus can greatly enhance oil recovery.