The Research On Numerical Simulation Theory Of Surfactant Microemulsion Flooding In Low Permeability Reservoirs

With the continuous advance of oilfield development process,most of China's conventional oil fields have entered a high or ultra-high water cut stage and the recovery has been in a well station,and the potential to get the further recovery is thin.In recent years,the majority of the newly discovered blocks belong to low-permeability reservoirs.Therefore,get the high-efficiency to achieve the effective utilization of low permeability reservoirs is in great significance to China's energy security and development.The low permeability reservoirs are with the characteristics of extremely small pores,large pore-throat ratio,large tortuosity,and the influence of the pore wall on the fluid in the pore must be considered.In view of the presence of boundary layer fluid,there is a threshold pressure gradient in the fluid in the pores and the flow law is no longer consistent with Darcy seepage.Thence,a higher pressure drop is needed to achieve effective movement of the fluid in the low permeability reservoirs.Aiming at the phenomenon about the difficulties of poor water injection and low oil recovery in Fuyang oil layer,the numerical simulation of microemulsion flooding in low permeability reservoirs has been studied in this paper.The microstructures and the threshold pressure gradient under the microemulsion flooding had been measured with the natural cores.The corresponding nonlinear seepage equation has been established based on the experimental data.Because the microemulsion system has the mechanisms of improving the recovery with ultra-low interfacial tension,changing the reservoir wettability to reduce the starting pressure gradient,the better flow control,changing the relative permeability of oil and water phases,the quantitative description of the surfactant adsorption,the change of viscosity,the change of the phases,the interfacial tension and the relative permeability curves have been obtained based on the experimental study.Considering the adsorption and diffusion of surfactant in the reservoir,a mathematical model of microemulsion flooding in low permeability reservoir with three-dimensional three-phase five-component was established.And IMPES method was used to get the numerical solution and the corresponding simulation software had been compiled.The microemulsion flooding experiment was carried out by using the plate core to verify the model.The surfactant concentration,the surfactant concentration and the salt concentration were optimized in the microemulsion process of Fuyang oil layer.The results of this study are of great significance for the effective development of low permeability reservoirs.