煤层气与常规天然气成藏机理的差异性

为弄清煤层气与常规天然气成藏的异同处，给煤层气的勘探开发提供科学参考，通过对煤层气与常规天然气的地球化学特征、储层特征、气体赋存形式、成藏过程及机理的对比分析，揭示了煤层气与常规天然气成藏的差异性：①煤层气以甲烷为主且成分简单，而常规天然气成分相对复杂；②煤层气主要以吸附态储集于煤岩微孔和过渡孔的表面，常规天然气以游离态存在于储层孔隙或裂缝中；③煤层气藏均经历了晚期抬升过程，后期保存条件好坏是能否成藏的关键，常规天然气成藏经历了生烃、运聚和保存与破坏演化过程，天然气形成的静态地质要素和天然气成藏过程的动态地质作用的最佳时空匹配是成藏的关键；④煤层气的聚集受水势、压力的控制，往往具有向斜富集的特征，而常规天然气聚集受气势的控制，往往具有背斜或高部位富集的特征。

Difference of gas pooling mechanism between coalbed methane gas and conventional natural gas

To make it clear the difference of gas pooling between CBM gas and conventional natural gas and provide good reference for scientific exploration and development of CBM, this paper makes a comparative analysis of both in terms of geochemical properties, reservoir characteristics, modes of gas occurrence, gas pooling process and mechanism, etc., and demonstrates their differences as follows: (1) The components of CBM gas are quite simple with methane as its main part, while those of conventional natural gas are relatively complicated. (2) CBM gas is accumulated and preserved at an adsorption state at the surface of micropores and transition pores in the coal rocks, whereas conventional natural gas at a free state in the pores or fractures of reservoirs. (3) The CBM gas pooling has experienced late tectonic uplift and the most important point is that the preservation occurred at the later stage, while the conventional natural gas pooling has experienced hydrocarbon generation, migration, accumulation, preservation, and failure evolvement, and its key point is that the dynamic geological process corresponds with natural geological conditions at proper time and place. (4) The accumulation of CBM gas is controlled by water state and pressure and usually accumulated at the syncline structures, while the latter is controlled by gas state and accumulated mostly at anticline structures or at higher locations of the structure.