PRESSURE BEHAVIOR ANALYSIS FOR COAL-BED GAS FLOW THROUGH DOUBLE PERMEABILITY MEDIUM IN DEFORMED COAL-BED GAS RESERVOIR
变形介质煤层气双渗流动压力分析

For the stress-sensitive coal-bed gas reservoir, traditional studies assume the formation permeability is constant. However, the assumption will result in significant errors in the estimation of variation of pressure. In this paper, the pressure transient response of the double porosity and double permeability media permeability in stress-sensitive coal-bed gas reservoir is studied. Not only the double permeability feature of coal-bed gas reservoir but also the deformation of medium in stress-sensitive coal- bed gas reservoir is considered, and the mathematical model of the double porosity/double permeability medium in stress-sensitive coal-bed gas reservoir is built. The numerical solution for a constant rate production of a finite radius well is obtained by using Full-implicit difference and Newtonian iterative method in an infinitely large system and finite closed system. The change rule of pressure are discussed when the parameters of double porous medium and the parameters of deformation change. The plots of type pressure curve are given in a few cases. The result can be applied to well test analysis.