煤岩润湿性对煤层气赋存的影响机理  

Mechanism of coal wettability on storage state of undersaturated CBM reservoirs

作　　者：朱苏阳[1] 孟尚志[2] 彭小龙[1] 李相臣[1] 张千贵[1] 张斯 ZHU Suyang;MENG Shangzhi;PENG Xiaolong;LI Xiangchen;ZHANG Qiangui;ZHANG Si(Petroleum Engineering School,Southwest Petroleum University,Chengdu,Sichuan 610500,China;Zhonglian Coalbed Methane Co.,LTD.,Beijing 100000,China)

机构地区：[1]西南石油大学石油与天然气工程学院,四川成都610500 [2]中联煤层气有限责任公司,北京100000

出　　处：《油气藏评价与开发》2022年第4期580-588,595,共10页Petroleum Reservoir Evaluation and Development

基　　金：中国工程院战略研究与咨询项目“我囯煤层气有效开发发展战略研究”(2021-XY-25);国家自然科学基金青年基金“基于煤粉群运移动力学特征的煤层气—水—固耦合传质机理研究”(52104036)。

摘　　要：岩石对流体的润湿性决定了孔隙中流体的分布特征,多孔介质中的小孔隙优先被润湿相流体占据。基于这一原理,分析了目前煤岩润湿性实验与煤层气赋存状态的矛盾,从煤岩润湿性的角度,提出了两种可能的煤层气宏观赋存模式。如果煤岩亲气,甲烷在毛管压力的作用下,可以被割理中的水封闭在煤基质中。由于煤基质和割理界面处的毛管压力,煤层气的吸附是平衡的,但赋存可以出现欠饱和状态,这也是排采过程中出现临界解吸现象的原因。当煤岩水相润湿时,水相需要占据煤岩中的小孔隙(基质),甲烷可以通过液相吸附的形态储存在基质中。液相吸附中,排采过程的临界解吸源自欠饱和的煤层气溶解状态。通过煤层气液相吸附的验证实验,也表明甲烷可以通过液相吸附的形式大量赋存于煤层中。The wettability decides the fluid distribution in porous media,and the wet-phase fluid will primarily occupy the smaller pore.Based on this principle,the paradox between laboratory test of coal wettability and state of fluids distribution is analyzed.On the view of wettability,two possible coalbed methane(CBM)storage types are proposed.When the coal is gas-phase wettability,owing to capillary pressure,the free gas and adsorption gas can be trapped in matrix(smaller pore system)by the water in cleat(larger pore system).In matrix system,the sorption of gas is in equilibrium state,but the storage of gas is in the undersaturated state.The critical desorption process results from the capability pressure of water and gas.When the coal is water-phase wettability,the matrix is saturated by water,and the coalbed methane can store in the matrix in liquid-phase sorption state.This study designs the experiment to validate the gas liquid-phase sorption.The results indicate that a mass of methane can be adsorbed in the matrix in the liquid-phase sorption mode.

关 键 词：煤层气 润湿性 气相赋存 液相吸附 欠饱和赋存 欠平衡吸附 

分 类 号：TE122[石油与天然气工程—油气勘探]