Application of Douglas-Jones predictor-corrector method in fractal coalbed methane reservoir
Received:June 10, 2014  Revised:September 23, 2014
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KeyWord:coalbed methane  fractal parameter  double porosity  Douglas-Jones predictor-corrector method  numerical solution  pseudo steady-state
宣英龙 中国石油勘探开发研究院 提高石油采收率国家重点实验室, 北京
马德胜 中国石油勘探开发研究院 提高石油采收率国家重点实验室, 北京
王树坤 大庆油田第五采油厂, 大庆
张永琪 中国石油山西煤层气勘探开发分公司, 晋城
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      Conventional mathematical models of coalbed methane were mostly based on Euclid Geometry and difficult to describe the complexity of pore structure and the irregularity of shape.In this paper,basing on fractal theory,new percolation models with the double porosity in fractal fracture network were established by introducing fractal parameters to describe the complexity of pore structure and the adsorption effect in coal bed.In the low permeability reservoir,the partial differential equation is nonlinear,so the numerical calculation is carried with the Douglas-Jones predictor-corrector method.The numerical solution of the pseudo-steady sorption formulation with constant rate production and the unsteady sorption formulation with constant rate production in a infinitely large system and finitely closed system were obtained.Analysis pressure transient with fractal parameters,draw typical pressure curves.Produced with constant rate in an infinitely large system,fractal dimension influences the pressure small in the early stage,but in the later stage,the smaller the fractal dimension,the higher the pressure.Produced with constant rate in a finitely closed system,fractal dimension has a great influence on the pressure in the early stage,pressure drops with the increase of fractal dimension,pressure first increases and then decreases with the reduction of fractal index,the pressure tends to the same value finally.