煤层气地质学基本问题的探讨

煤层气是一种由煤生成,以CH₄为主的非常规气。它与常规气藏不同,主要以吸附状态储集在煤岩过程中形成的三维储集网络内,其储集量远大于储存在孔隙、裂隙中的游离气和溶解气量。正是这一特点决定了煤层气的运移、扩散微弱,易于大面积成藏。在地质历史演化过程中,后期构造相对稳定、水动力系统完好、煤层处于封闭状态是形成良好煤层气藏的必要条件。成煤期具有全球意义,我国与全球有极为相似的分期特征,出现在阿尔卑斯和华力西两个构造期。我国5个构造区分属以陆块为代表的稳定区和以陆缘为代表的活动区,其中塔里木华北区和华南区为稳定区,几个成煤期都利于煤层气盆地的成生与保存。

AN APPROACH TO ESSENTIAL ISSUES OF COALBED GAS GEOLOGY

Coalbed gas is a kind of unconventional and coal formed gas that is mainly composed of methane.The gas is preserved in 3-D reservoir networks in the coalbeds.Its reserve is much greater than that of free gas and dissolved gas preserved in pores and fractures.It is this property that decides the gas migrating and dispersing weakly and preserving easily in large areas.In geological evolution,the existence of stable post structures,complete hydrodynamic system and well sealed coalbeds are necessary for the formation of coalbed gas reservoirs.China's five tectonic regions are situated respectively in stable regions(represented by continent blocks)and active regions(represented by continental margins).Among them,Tarim-North China and South China regions are stable ones,the coal-forming stages of the regions were favourable for the formation and preservation of coalbed basin.