沁水盆地煤系天然气系统富集成藏的主控因素分析

沁水盆地是我国最大的构造聚煤盆地,也是国内首个实现煤系天然气商业化开采的区块。盆地内石炭-二叠系煤层厚度大、分布稳定、吸附能力强、含气量大,目前产能已超过20×108m3,具有良好的勘探开发潜力。以煤田、煤系天然气勘探阶段积累的资料为基础,系统探讨了沁水盆地煤系天然气富集成藏的主控因素,分析认为构造演化、埋藏史和热演化、沉积体系和水文地质条件是控制沁水盆地煤系天然气富集成藏的主要地质因素。沁水盆地两期生气都是在构造运动的影响下发生,煤系赋存状态为印支、燕山和喜山期构造运动叠加的结果,断裂及陷落柱发育区含气量低;区内煤层埋深呈现北部深南部浅,中部深东西部浅的特点,南部热演化程度高,煤系天然气含量大;沉积体系影响煤层的空间展布;水文地质条件关系着煤系天然气的形成和保存,弱水动力区为煤系天然气的有利区。

Analyses on Enrichment and Reservoiring Main Controlling Factors of Gas in Coal Measure Qinshui Basin

Qinshui basin is not only the largest tectonic coal accumulating basin, but also the first blocks to achieve commercial exploitation of gas in coal measure. The distribution of Carboniferous- Permian coal seam which has a large thickness is stable, the coal seam has strong adsorption capacity and large gas content in the basin, the current production is more than two billion square, so it has a good potential for exploration and development. Based on accumulated data of coal and coal gas exploration stage, we explore the main controlling factors on Qinshui Basin gas enrichment and accumulation in coal measure systematicly. The research shows that tectonic evolution, burial history, thermal evolution, depositional system and hydro-geological conditions control Qinshui Basin gas enrichment and accumulation together, and they are major geological factors. Two periods of natural gas in Qinshui Basin appeared in the tectonic movement, and the tectonic evolution controls the formation of gas in the coal measure obviously; depth and thermal evolution control the center of gas production in the plane, the strength of evolution controls the coal rank, then controls the size of the gas content; depositional system affects the spatial distribution of the coal; hydro-geological condition is related to gas in coal measure formation and preservation.