湘中涟源盆地石炭—二叠系煤层气气源岩特征与资源评价

位于湖南中部的涟源盆地，发育一系列北东—北北东向的短轴向斜，面积近６０００ｋｍ２。盆地内有下石炭统侧水组和上二叠统龙潭组两套煤系，煤层主要分布于向斜中。两套煤系的煤层均为腐殖煤，有机质属Ⅲ型干酪根，具较强的生气能力。煤岩中原生小气孔占９０％以上，也有次生气孔和内生、次生裂隙，这就决定了煤层气的赋存以吸附状态为主，游离状态为辅。煤层气的组分主要为甲烷，含微量重烃气及非烃气。煤层的渗透率总体较低，但通过解放储层开采的措施，可显著提高渗透性以利于煤层气的抽放。根据煤层气资源评价结果，可在盆地内划分出３个高、中富气区，而两煤系煤层气的开发远景区均在靠近盆地南缘龙山东西向隆起带的各含煤向斜西南仰起端及其附近。

THE CHARACTERISTICS OF GAS GENERATING ROCK AND RESOURCES ASSESSMENT OF COALBED METHANE OF CARBONIFEROUS PERMIAN SYSTEM IN LIANYUAN BASIN,MIDDLE HUNAN

Located in the centre of Hunan Province and with an area about 6 000 km 2,Lianyuan Basin has a series of NE NNE trend brachy synclines,there are Lower Carboniferous Ceshui and Upper Permian Longtan coal measures in the Basin,and the coal beds are mainly distributed in the brachy synclines. The two sets of coal measures are humic coal with kerogen and strong gas generating.The small primary vesicles of coal rock are more than 90%,the secondary vesicles,endogenetic and secondary cracks also exist in coal,which make the coalbed methane be mainly adsorbed gas,and the free gas secondarily.The gas contains methane primarily,weight and non hydrocarbons gas slightly.The permeability of coal is low,but it can be improved by stimulating gas bearing reservoir.According to the results of resources assessment of the coalbed methane,three high,middle gas bearing zones can be located,and the prospective areas of gas exploitation are in southwest upwarping hinge and its vicinities of the brachy synclines near E W trend Longshan mole track at the southern edge of Lianyuan Basin.