Study On Numerical Simulation Of Low-salinity Water Flooding To Enhance Oil Recovery

Compared with normal water flooding,low-salinity water flooding has the advantages of low cost,low pollution,and wide application scope.And it is very important for improving the recovery and economic benefits under the situation of low international oil prices.In recent years,a large number of experiments and field practice show that low-salinity water flooding can improve oil recovery economically and efficiently.However,this technology has not been paid much attention in China,and the related research is still blank.The coupled fluid-solid in low salinity water flooding is very complicated and hard to research.Based on the microcosmic reaction in porous media,the mechanism of low-salinity water flooding is explored in this paper.Combined with diffusion double layer theory and the stability theory of colloid particles,the amount of migration fine particles and permeability damage are analyzed.Considering the changes of reservoir parameters,the mathematical model of low salinity water flooding is established and solved by Newton-Raphson iteration method.Then in this paper,the development effect of low salinity water flooding and conventional water flooding in different reservoir models are compared.The results show that the concentration and valence of salt ions in the injected water have a great influence on the Zeta potential on the rock surface,and can affect the stability of the clay particles on the rock surface.When the salinity of the injected water is low,the clay particles are separated from the surface of the rock and migrated with water flow.Thus the effective permeability of water decrease which reduced the velocity of water.The particle migration occurs mainly in the region of low salinity water waved.The permeability damage of the high permeability layer is more significant than the low permeability layer,and the penetration phenomenon of the hypertonic layer is relieved.Several examples of low salinity water flooding model is solved in this paper.In the two-dimensional homogeneous model,low salinity water flooding can slow down the plane fingering.In the development of multilayer heterogeneous reservoirs,low salinity water flooding slow down the dart of high permeability layer water and promote equilibrium displacement.