Application Of Streamline Method For Study On Water Flooding Development Characteristics In Anisotropic Oil Reservoirs

Anisotropy is a main factor affecting reservoir development,and it is important to analyze the influence of anisotropy on injection-production coupling relationships and development effects of areal well patterns.Because of its advantages of fast computational speed and easily visualized simulation results,streamline method is useful for identifying injection-production coupling relationships and calculating the development effect rapidly in anisotropic oil reservoirs.Based on single phase steady flow theory,flow fields of areal well patterns in anisotropic oil reservoirs are calculated and analyzed.First,coordinate conversion method is used to transform the anisotropic oil reservoir into an equivalent isotropic oil reservoir,and the pressure distribution function is derived with stress superposition principle,and the streamlines are calculated;secondly,according to the distribution characteristics of streamlines,the injection-production coupling relationships are determined,and the destruction and reconstruction effects are proved in anisotropic oil reservoirs.The relationships between anisotropy and destruction effects are analyzed.Besides,the effects of corner-to-side production well rate ratio on the development of inverted nine-spot patterns are also analyzed further.To obtain better development effects of areal well patterns in anisotropic oil reservoirs,simple functions which can be used to design reasonable parameters of well patterns are given.Considering the effect of capillary force,the streamline numerical simulation method for anisotropic oil reservoirs is built.The pressure equation with full permeability tensor is solved using nineteen-points finite difference scheme,and the velocity profile is calculated using Darcy's law,and then the distribution of streamlines and TOF are also calculated using Pollock's method.Along the streamlines,the saturation equation is solved with the method of characteristics(MOC)analytically,or with the finite difference method numerically.For the saturation equation which contains the capillary force,the orthogonal operator splitting method,which can decomposed the capillary force into two components:one part is parallel to streamline,and the other part is perpendicular to streamline,is used to solve the capillary problem.The results show that this orthogonal operator splitting method can improve computational efficiency.Considering imbibition effect between fracture and matrix,the streamline simulation method for fractured anisotropic oil reservoirs is built.The calculation process of flow fields is the same with the common anisotropic oil reservoir.Using empirical transfer function,saturation equation of dual porosity medium is solved analytically with MOC;Using Pc-based transfer function,saturation equation is solved with an explicit backward difference method.The results show that the oil recovery from imbibition displacement is the main development scheme for fractured oil reservoirs.The effects of permeability,capillary force,oil/water viscosity ratio and surface tension on the imbibition recovery are discussed,and the influence of anisotropy on the development of fractured oil reservoirs is also discussed.