煤层气在非饱和水流阶段的非定常渗流摄动解

煤层甲烷由煤层的割理裂隙系统流入生产井一般经历：单相水流、非饱和流和气、水两相饱和流三个阶段，在非饱和流阶段，储层压力降至临界解吸压力之后，储存在煤基质中的吸附气体少量被解吸出来形成互不连续的气泡并阻止水的流动，含气量尚未达到饱和程度。同时煤层甲烷运移包含渗流场、变形场和应力场的动态耦合过程。本文考虑渗流过程中水-气两相不溶混流体与固体耦合作用，建立了非饱和水流阶段非定常渗流问题的流固耦合数学模型，对该强非线性一维数学模型采用摄动法和积分变换法进行解析求解，并讨论了其压力动态特性，分析了压力随饱和度S及时间t变化的规律和气相及耦合作用的影响，这些研究对煤层气、石油和天然气的开采等地下工程领域具有一定的指导意义。

The Perturbation Solution of Unsteady Seepage in Coalbed Methane Unsaturated Water Flow Phase

Coalbeds are characterized by their dual porosity, which contains both matrix and cleats porosity systems. The matrix porosity system contains the vast majority of the gas volume, while the cleats porosity system provides the conduit for mass transfer to the wells. Coalbeds methane flow through cleats to production wells includes three phases: single phase water flow and both unsaturated water flow and saturated water flow. In the unsaturated water flow phase, when the cleats system pressure drops, gas molecules desorb from the matrix porosity interface and are released into cleats porosity system. As a result, desorbed gas forms discontinue gas bubbles, which hold back water flow. At the same time, the coalbeds methane transport includes the coupling process of seepage field, deformation field and stress field. In the paper the fluid solid interaction and desorbed gas affect water transport are analyzed. A coupled mathematical model of unsteady seepage in coal methane unsaturated flow phase is established based on the theory of fluid solid interaction. The nonlinear mathematical model is investigated by using the perturbation and integral transform. Pore pressure along level distance at different saturation and time, and gas phase effect on seepage flow under coupling and without coupling conditions are discussed. Some valuable conclusions were got.