煤层渗透率敏感性及其对煤层气开发效果的影响

煤层由裂隙和基质组成，为双重孔隙系统。前者由割理和后生裂隙组成，为煤层气的渗流通道；后者是煤层气的主要储集空间。煤层渗透率是进行煤层气商业开发的重要评价参数，而渗透率变化规律及其对煤层气动态开发效果的影响情况则亟待进一步研究和验证。在总结分析前人研究的基础上，对煤层气有效应力变化模型进行了研究和验证，进而分析了渗透率动态变化对煤层气开发效果的影响。结果表明：在煤层气开发过程中，煤层渗透率受裂隙压缩和基质收缩的双重影响，渗透率呈现先降低后升高的特点；基质收缩起到改善煤层气渗透率的效果，能够有效地提高煤层气开发效果，故在煤层气开发中不能忽视其影响。

SENSITIVITY OF COALBED PERMEABILITY AND ITS INFLUENCES ON PRODUCTION OF COALBED METHANE

Coal bed is characterized by a double porosity system composed of fissures and matrix. The fissures consist of cleats and epigenetic cracks and act as flow pathways of coalbed methane, while the matrix provides the main reservoir space for accumulation of coalbed methane. Coal bed permeability is an important parameter for evaluation of commercial development of coalbed methane. The pattern of permeability variation and its influences on performance of coalbed methane recovery need further study and verification. Based on summary and analysis of previous studies, the effective stress model of coalbed methane is studied and verified, and the influences of permeability variation on coalbed methane production are analyzed. The results show that coal bed permeability is under the dual impacts of fissure compression and matrix contraction and is characterized by decreasing at first and then increasing. Matrix contraction can improve coal bed permeability, thus can effectively enhance the recovery of coalbed methane. Therefore, its influences shall not be overlooked during production of coalbed methane.