变形介质煤层气双渗流动压力分析

PRESSURE BEHAVIOR ANALYSIS FOR COAL-BED GAS FLOW THROUGH DOUBLE PERMEABILITY MEDIUM IN DEFORMED COAL-BED GAS RESERVOIR

研究了应力敏感煤层气中双孔隙度/双渗透率渗流问题的压力不稳定响应,不仅考虑了煤层气藏的双孔隙度/双渗透率介质特征,而且考虑了介质的变形,建立了应力敏感煤层气双孔隙度/双渗透率的数学模型,采用全隐式差分和N ew ton迭代法求得了圆柱面井源情况下定产量生产时无限大地层、有界封闭地层的数值解,探讨了双孔隙度/双渗透率参数和变形参数变化时压力的变化规律并给出几种情况下典型压力曲线图版。

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.