Study On The Influence Of Fractured Horizontal Joint On Oil Well Productivity

In the process of oil or gas development, hydraulic fracturing is an important measure for improving well productivity. In some shallowly buried reservoirs and reservoir with abnormal high pressure, hydraulic fracturing is prone to create horizontal fractures. There are only a few researches on influences of horizontal fractures on well productivity. Existing studies have the deficiency of lack of specificity and complex problem solving process.In recent years, with the development of computer hardware and software technology, reservoirs with complex geological characteristics can be simulated and accuracy is improved greatly. In this paper traditional productivity evaluation methods were combined with nu-merical simulation technologies. Based on numerical simulation and horizontal fracture re-lated theories, following studies were conducted:(1) formation conditions, geometry of hy-draulic horizontal fractures and characteristics of reservoir fluid flow in fractured formations;(2) numerical representation of horizontal fractures;(3) influence of permeability anisotropy, reservoir aspect ratio, propped volume, vertical location and shape of fracture on well produc-tivity;(4) optimized fracture size and well productivity of different conditions in depletion process;(5) influences of horizontal fractures on oil well in5-spot,9-spot or7-spot patent water injection cases.After comprehensive analysis, following conclusions are made.(1) The critical depth of creating horizontal fractures during hydraulic fracturing is essentially determined by in-situ stress conditions. When in-situ stress was changed by developing process, the critical depth will be changed accordingly.(2) The grid generation program described in this paper can effi-ciently convert results of existing fracturing simulation programs to reservoir simulation pro-gram, which can make up the inadequacy of existing reservoir simulation programs.(3) The program to calculate optimized fracture size (conductivity) under different conditions was proved to have engineering feasibility.(4) For low permeability reservoirs, hydraulic fractur-ing can enhance oil recovery efficiently.(5) Shape and angle of horizontal fractures have great effect on oil well productivity in water injection process.(6) In reservoirs with hydraulic hor-izontal fractures, fracture shape and angle must be monitored before water injection and ap-propriate well paten can improve oil recovery.