School of Energy Resources,China University of Geosciences ( Beijing) Lab of Coal Reservoir,NationalEngineering Research Center of Coalbed Methane Development and utilization Engineering and TechnologyBranch,CNOOC Energy Technology and Services Company Limited New Energy Research Center,CNOOC Research Institute

为准确表征开发过程中欠饱和煤储层孔隙度变化,以临界解吸压力为界,在煤基质收缩及有效应力耦合作用下建立煤储层孔隙度模型,以此分析了排采过程中孔隙度随孔隙压力的变化规律。研究结果表明,开发过程中孔隙度变化一般经历4个阶段:排水降压段、缓慢降压段、弥补反弹段、快速增长段,分别与生产过程中气、水产出变化阶段相对应;孔隙度变化程度主要受控于反弹压力点与临界解吸压力点之间的配置关系,反弹压力越接近临界解吸压力,基质收缩强度越大,孔隙度反弹能力越强;在生产过程形成的压降漏斗内,各点孔隙度变化可以反映该点储层压力的变化,扩大压降漏斗内孔隙度反弹压力面和等孔隙度压力面,有利于提高煤层气井产能。

in order to accuratels characterize the porosity vaiation of the less saturated coal reservoir during the development process a porosity model of the coalreservir was esablished based on thecitial desorptio pressure as the boundary and in consideration of the cal matix shinkage and fctivestress couping roleThus with the variation law of the porosity pressure the porosity during the mining process was analyzed. The study resuts showed that in the development prcess.theporosit varation would have four sages and thy would be the water drainage and prssure releasing stage the sow pressure releasing stage supplement rebound stage and rapid increasing sag .Those stages would be relevant to the gas and water output variaion stage in the producion process.The porosity variation degree wasmanly contrlled by the confguration relationship betwee the rebound pressure pit and the crtitaldesorpticn pressure. when the rebound pressure was closed fo the critical desopion pressure the matik shrinkage strength would be higher and the rebound capacityof the porosity would be sronger:Within the pressure released hoppe formed durng the producton proc.ss,each poit porosity variation could refect the pressurevariation of the coal reservir.could expand the rebound pressure surtace of theporosity in the prssure released and hopper and theporosity pressure suface and could be favorableto inprove the producion capacityof the coalbed methane well.

国家科技重大专项资助项目(2016ZX05042-002)；国家自然科学基金资助项目(41272175)；中央高校基本科研业务费专项资金资助项目(2652015331)；