Study On Unsteady Seepage Theory And Well Testing Of Horizontal Wells And Horizontal Wells In Low Permeability Gas Reservoirs

Recent years, horizontal well and fracturing horizontal well technology has been developed greatly in the low permeability gas reservoir development. Meanwhile the seepage rule of horizontal well and fracturing horizontal well is more and more regarded by scholars. Horizontal well developing involves gas engineering、fluid mechanics in porous medium,gas recovery and calculation science and so on, it is a complex system engineering. In home and overseas,many academicians make researches about horizontal well filtration theory, but these researches mainly based on oil reservoir field and Darcy linear flow.Literatures about unstable seepage theory in horizontal and fracturing horizontal wells are seldom been reported.The object is to study the seepage problem in low permeability gas reservoir. With the combination of modern fluid mechanics, well test analysis, mathematical physics, computer programming and other subjects knowledge, in the conditions of different media, we make a series of researches on unstable seepage theory, well test analysis methods of horizontal and fracturing horizontal wells in low permeability gas reservior.The main works accomplished in this article are as follows:(1)Based on the extensive research on domestic and foreign literature, the reservoir and micro-flow characteristics of low permeability gas reservoir are summarized.(2) Starting from the seepage principle of low permeability gas reservoir, considering the effect of trigger pressure gradient, an unstable flow mathematical model of horizontal well in homogeneous and dual media low permeability gas reservior has been established. Solving the model with Laplace transform and orthogonal transform, we can obtain the Laplace space solution under different outer boundary conditions. At last, we draw the pressure response curves,then divide the pressure response curves into several phases and analyse the effects of relevant parameters.(3)An unstable seepage model of infinite conductivity fracturing horizontal well in homogeneous and dual media low permeability gas reservior has been established. The cracks discrete mechanism has been introduced in the model. Solving the seepage model with semi-analytical method, we draw the pressure response curves, divide the pressure response curves and analyze the effects of relevant parameters.(4)An unstable seepage model of finite conductivity fracturing horizontal well which consider the flow resistance of artificial cracks in homogeneous and dual media low permeability gas reservior has been established. Solving the seepage model with semi-analytical method, we draw the pressure response curves and divide the pressure response curves into several phases.(5)Real well test data are analyzed by well test models of low permeability reservoirs which are established in this article. The results verify the proposed well test interpretation theory.