Study On Productivity Prediction Of Directional Wells In Low Permeability Reservoirs

Compared with the conventional reservoir,the starting pressure of non-linear seepage is low due to the existence of non-linear seepage gradient.At present,the models describing nonlinear seepage include quasilinear seepage model and continuous seepage model.Because the quasi linear seepage model can not fully reflect the seepage characteristics of low permeability reservoir,the quasi linear seepage model used in conventional and fractured directional wells in low permeability reservoir can not accurately calculate the productivity.Therefore,according to the start-up pressure gradient experiment and mathematical derivation,this paper obtains the continuous seepage model,establishes the Darcy model,quasi linear seepage model and continuous seepage model productivity formula of conventional and fractured directional wells through conformal transformation,calculates the productivity under the three seepage models and compares it with the real oil well productivity,and then carries out the productivity sensitivity analysis and the multi-layer combined production based on considering the interlayer interference coefficient Prepare productivity prediction software for productivity formula of fracturing directional well.Through the research of this paper,the following understandings and results are obtained:1.Taking a reservoir in Jidong Oilfield as the object,the quasi linear seepage model and continuous seepage model in line with the nonlinear seepage law of Jidong reservoir are established.The error between the seepage curve calculated based on the continuous seepage model and the real seepage curve is 8%,which can better reflect the nonlinear seepage law of low-permeability reservoir.2.By comparing the productivity of conventional and fractured directional wells in low permeability reservoir with that of actual directional wells,it is obtained that the productivity error of Quasilinear seepage model is greater than that of continuous seepage model,which shows that quasilinear seepage model can not fully reflect the seepage characteristics of low permeability reservoir,and the productivity of continuous seepage model can calculate the productivity of directional wells more accurately.3.By analyzing the influencing factors of production radius,it is found that the production pressure difference and mobility are in direct proportion to the production radius;Under the same production conditions,the production radius of nonlinear starting pressure gradient is close to the real production radius of oil well.4.The sensitivity analysis of productivity of conventional and fractured directional wells in low permeability reservoir shows that the half length of fracture,well deviation angle and production differential pressure are directly proportional to productivity,and the stress sensitivity coefficient is inversely proportional to productivity.5.According to the conventional multi-layer combined production in low permeability reservoir and the productivity formula of fracturing directional well,the productivity prediction software can predict the multi-layer development output of directional well and carry out productivity sensitivity analysis.