Study On Technological Policy Limits Of Separate-layer Water Injection

Most of China's oil fields are developed by water injection,and there are serious contradictions between layers.Separate-layer water injection is an effective means to alleviate interlayer contradictions and improve oilfield development effect.However,the traditional method of dividing the technical policy boundaries of separate-layer water injection has various limitations and there is a lack of a set of quantitative and reasonable methods for dividing technical policy limits.Therefore,it is necessary to conduct a systematic and in-depth study on different stages and situations of oilfield development,and establish the technical policy limits system of separate-layer water injection at different stages of development.A series of typical models of injection-proportion wells with different rhythms were established,considering the influence of reservoir physical property difference,pressure difference,layer number difference and interval length on water absorption and liquid production capacity of each layer.Numerical simulation study of multi-layered injection was carried out on the model.The difference of water breakthrough time and the difference of watercut escalating rate were used respectively before and after water breakthrough to accurately characterize the impact of major factors.The lorentz coefficient was used to evaluate the vertical balance of the reservoir.The equilibrium displacement number and lorentz coefficient of each model was calculated to find the relationship between the equilibrium displacement number and the lorentz coefficient.The equilibrium displacement criteria were determined according to the warning values of lorentz coefficients.The limit value of the number was used as the technical policy limit of stratified water injection.The influence of each factor was deeply analyzed,and the dominant factors affecting the policy boundaries of stratified water injection technology were analyzed.Through the research,the technical policy limits system of separate-layer water injection with different development stages,different rhythm characteristics and different well pattern forms has been formed.It was concluded that permeability gradient and oil viscosity gradient are the main factors affecting the technical policy limits of separate-layer water injection.The application example showed that the policy limits of separate-layer water injection technology obtained by the study can provide convenience and guidance for field development.