Theory Of Fluid Porous Flow For Mixed Well Patterns And Its Application In Well Spacing Optimization

Well pattern is the most important affecting factor to the ultimate recovery for an oilfield. The classic fluids rate forecast methods cannot meet the needs of low-permeability reservoir, horizontal wells and fracturing well patterns. Based on the theory of reservoir engineering, a series of methods have been put forward to forecast the output of oil wells for these particular well patterns.Using the mirror image, principle of potential superposition to solve pseudo steady-state flow equations of an oil well or an injection well in a closed drainage area, the output of a well in an infinite well net can be obtained. The result got from this new method is close to the result from traditional method and the relative error is less than 3.91%, but it is more simple and easy to extend.Using the Fourier transform, principle of potential superposition, trigonometric function transform, asymptotic analyses, a pressure solution of a pseudo steady-state flow model in 3D circular-boxed media has been established. Comparing with the productivity of vertical well, an equivalence radius model can be obtained. Based on the equivalence radius model, the productivity of horizontal-vertical well patterns can be established for five-spot, anti-seven-spot and anti-nine-spot well net.A productivity formula for low permeability reservoir with oil or water wells fracturing has been ascertained. This formula can be used to get the output for a vertical injection well pattern or a horizontal injection well pattern. Using the material balance method, the water breakthrough time can be obtained. The general equations of productivity and water breakthrough time considering the threshold pressure gradient of low permeability reservoir, fracture length, pattern of spacing have been established in this dissertation.This dissertation presents the comparison with some widespreadly used methods and computes the oil well output for different parameters. Methods of productivity estimation for a mixed well pattern have been used to draw up the infill development program for Daqing Yushulin oilfield.