地应力对煤层气勘探与开发的影响

Influence of crustal stress on coal bed methane exploration and developing

地应力是指岩土体内一点固有的应力状态,煤层气是一种以吸附状态为主储存于煤层及其围岩中的非常规天然气。我国煤层气勘探与开发还处于初级阶段,而地应力对煤层勘探与开发有十分显著的影响,其影响主要包括以下三个方面:1地应力对煤储层渗透性、储层压力的影响;2地应力对煤层气的吸附、解吸、扩散和渗流的影响。地应力增加,储层压力增大,煤层吸附气体的量增多,但渗透率降低,给煤储层的排水、降压及煤层气的解吸、运移、产出造成一定困难;3地应力对天然裂缝目前在地下的附存状态及有效性,以及人工压裂裂缝的形态和延伸方向的影响等。所以十分有必要系统论述地应力对煤层气勘探与开发的影响。

The crustal stress is the state of stress of a point bears in the rock mass or soil body.Coal bed methane is a kind of unconventional gas resources that exist in the coal bed or its surrounding rock in the form of adsorption state.The coal bed methane exploration and developing is still at the primary stage in our country,and the crustal stress has great influence on coal bed methane exploration and development,and the influence mainly has three aspects as follows.Firstly,the crustal stress has great influence on permeability and pressure of coal reservoir.Secondly,the crustal stress has great influence on adsorption,desorption,diffusion,and seepage of coal bed methane.When crustal stress increases,the pressure and the amount of adsorbed gas increases,but the permeability decreases,and this goes against drainage,pressure lowering,and the desorption,migration,and production of coal bed methane.Thirdly,the crustal stress has great influence on the underground existence state and effectiveness of natural fractures at present,and it also influences the shape and extension direction of hydraulic fracture.So,it is very necessary to summarize the influence of the crustal stress on coal bed methane exploration and development.