火山岩侵入对低煤阶煤层气藏的影响

Effects of igneous intrusion on low rank coalbed methane reservoir formation

阜新盆地王营—刘家凹陷瓦斯涌出量远远超过煤层气吸附量,且成因复杂。对王营—刘家煤层气藏地质背景、气藏特征、气藏形成的关键因素进行了分析。研究表明气藏受辉绿岩墙影响非常显著,岩墙侵入不仅促使煤层气大量二次生成,也使得阜新组底部的油页岩成熟生气,作为主要气源补给,使地下水沿露头和岩墙向凹陷深部双向补给,构成滞流水及承压水封闭体系,并沟通水力联系,提供了煤层气扩散—运移通道;研究还证实了王营—刘家煤层气藏存在大量游离气,封闭性断层阻止了煤层气大量逸散,天然焦分布区域是王营—刘家凹陷煤层气开发的首选目标区,煤层气高产井沿岩墙呈环带状展布。因此,在低煤阶煤层气勘探中,可适当借鉴常规天然气勘探思路,采取常规天然气评价选区与煤层气地质研究相结合的办法。

In the Wangying-Liujia sag,Fuxin Basin,not only the CBM desorption volume is more than the adsorption gas,but the CBM origin is very complex.Research proves that the Wangying-Liujia CBM reservoir formation is greatly controlled by the diabase dike invasion,which is not only favorable for large hydrocarbon regeneration,but improves the Ro of the thick bituminite in the bottom of Fuxin formation,as the main gas origin.As the same time,the diabase dike invasion extremely improves the coal reservoir property,which is favour of the groundwater double replenishment following the coal seams outcrop diabase dike and the closed pressure water condition formation.Moreover,it is proved that there is abundant free gas in the Wangying-Liujia sag and the closed fault prevents gas diffusion.So the carbonite growing area is the most advantageous and the high production CBM wells will be distributed in the girdle band following the dike.In the same way,to the low rank CBM exploration,comparison the conventional nature gas research approach and combination the CBMconventional gas evaluation are important.