武乡南区块煤层气开发的深部地质边界研究

Research on deep geological boundary of coalbed methane development in Wuxiang South Block

为了开发利用新中标的武乡南区块煤层气资源,对深部煤层气资源的开采提供理论指导,基于地质分析与实验模拟相结合的思路与方法,结合模拟煤储层条件下的等温吸附与渗流实验,预测了深部煤储层含气性与渗透性随着埋深增大的变化特征,并发现了深部不同于浅部的变化趋势,指导了后期煤层气开发的工程实践。研究结果表明:深部煤储层压力与温度共同制约含气量的大小,且深部煤储层含气量发生转折的临界深度为1 820 m,超过这一临界深度含气量逐渐降低;深部煤储层温度与地应力共同制约渗透率的大小,且深部煤储层渗透率发生转折的标志埋深是1 600 m;鉴于深部煤储层低渗的特点,有效地对深部煤储层含气量、渗透率及其可改造性进行分析与探讨,认为煤层气开发的深部地质边界为埋深1 800 m。

In order to develop and utilize the coalbed methane resources of the newly-winning Wuxiang South block and provide theoretical guidance for the exploitation of deep coalbed methane resources,this article was based on the idea and method of combining geological analysis and experimental simulation,combined with the isotherm adsorption under simulated coal reservoir conditions and seepage experiment,predicted the change characteristics of deep coal reservoir gas content and permeability with the increase of buried depth,and found the change trend of deep part different from shallow part,which guided the later engineering practice of coalbed methane development.The research results showed that the pressure and temperature of deep coal reservoirs both restricted the size of gas content,and the critical depth at which the gas content of deep coal reservoirs turns wais 1820 m,and the gas content gradually decreased beyond this critical depth;the temperature of deep coal reservoirs together with the in-situ stress,the permeability was restricted,and the burial depth of the deep coal reservoir was 1600 m.In view of the low permeability of the deep coal reservoir,it could effectively control the gas content and permeability of the deep coal reservoir.Through analysis and discussion on its transformability,it was believed that the deep geological boundary of coalbed methane development was 1800 m deep.