煤层气井排采扰动下局部水动力场对排采的动态影响

The Dynamic Effect of Regional Hydrodynamic Field on the Drainage and Production under the Disturbance of Drainage and Production of Coalbed Gas Well

摘要:

煤层气主要以吸附态存在于煤层中，其产出需要历经解吸—扩散—渗流的过程。煤层气的产出过程说明，煤岩储层压力低于煤层气的临界解吸压力是煤层气解析产出的关键。排水降压是降低煤岩储层压力最为行之有效的方法，在排水降压的过程中会对地下原始水动力场产生扰动，在井周围形成局部水动力场，从而影响排水降压的效能。该文根据地下水的流动状态、区域构造发育状态，结合煤储层与含水层的组合关系，提出了煤储层排水降压过程可能出现有效扰动型、含水层水入侵型、地表淡水入侵型等3种局部水动力场，并结合实例分析了不同种类水动力场对煤层气排采的动态影响，对指导煤层气的排采具有实际意义。

Abstract:

Coalbed gas is mainly adsorbed in coal strata adsorptive state. Its output must experience the process of desorption—diffusion—seepage. The production process of coalbed gas indicates that the pressure of coal and rock reservoir is lower than the critical desorption pressure of coalbed gas, which is the key to the resolution output of coalbed gas. Drainage depressurization is the most effective method to reduce the pressure of coal and rock reservoir. In the process of drainage and depressurization, the original hydrodynamic field of underground water will be disturbed and the local hydrodynamic field is formed around the well, which will affect the efficiency of drainage and depressurization. According to the flow state of groundwater, regional tectonic development state, combining with the combination of coal reservoir and aquifer, 3 kinds of local hydrodynamic fields, such as effective disturbance type, aquifer water intrusion type and surface fresh water intrusion type are proposed in the process of coal reservoir drainage and depressurization, and different kinds of hydrodynamic fields have been analyzed combining with examples. The dynamic influence of CBM drainage is of practical significance for guiding CBM production.