沁水盆地南部煤层气成藏机理

RESERVOIRING MECHANISM OF COALBED METHANE IN SOUTHERN QINSHUI BASIN

煤层气成藏机理研究是煤层气勘探开发的前提和基础。为此,以油气、煤田和煤层气各勘探阶段积累的资料为基础,结合前人的研究成果,系统探讨了沁水盆地南部煤层气藏的成藏机理。通过对煤层气藏特征(包括煤层空间几何形态、煤层气成分和含量、储层物性、吸附特征、储层压力及封闭条件)和煤层气成藏过程(包括煤层气形成、运移和聚集)的分析,进而认识到:晚古生代煤层在经历了印支期和燕山期两次煤化作用后大量生气,并在喜山期遭受了强烈的调整与改造作用,最后逐渐形成了现今的沁水盆地南部煤层气藏;直接控制和影响该区煤层气富集的因素除了煤层顶底板的岩性与边界断层外,地下水的补给、运移、滞流和排泄也是关键因素;该区目前的高产煤层气井基本上都位于地下水滞流区。

Research on the reservoiring mechanism of coalbed methane is the basis of exploration and development of coalbed methane. Based on the data accumulated in various stages of exploration of oil and gas, coal and coalbed methane and in combination with the previous results of research, this paper systematically discusses the reservoiring mechanism of coalbed methane in the southern Qinshui Basin, and analyzes the features of coalbed methane reservoirs, including the spatial geometry of coalbed, the compositions and contents of coalbed methane, poroperm characteristics of the reservoirs, characteristics of adsorption, reservoir pressure and sealing conditions, and the process of reservoiring of coalbed methane, including the generation, migration and accumulation of coalbed methane. It is believed that the Upper Paleozoic coal seams went into peak generation of methane after two stages of coalification in the Indo-Chinese and Yanshan epochs and were strongly adjusted and modified in Himalayan epoch, resulting in the formation of the current coalbed methane pools in the southern Qinshui Basin. In addition to the lithologies of the adjacent rocks and the boundary faults, the recharging, movement, stagnation and discharging of ground water are also key factors which directly control and influence the enrichment of coalbed methane. The current coalbed methane wells of high capacity are basically located in the stagnant zone of groundwater in the study area.