中国煤层气赋存特点与勘探方向

中国煤层气资源十分丰富,特点表现为含煤盆地多、含煤层系多、煤种全、煤层气藏类型多。埋藏深度浅于1000m的资源量达14.27×1012m3,是目前煤层气开发的主要对象。当前国家配套扶持政策基本到位,是我国发展煤层气的重要机遇期。加快煤层气发展,首先要认识其赋存特点,选准富集区,探好目标区。近年来的研究成果表明,中国煤层气主要富集在5类地区:区域含煤区构造高点、直接盖层稳定分布的上斜坡区、凹中隆构造的火山岩活动区、浅层封闭条件好的低煤阶与厚煤层发育区、断裂活动次生割理发育区。目前,我国尚处于煤层气开发的初期,勘探开发前景广阔。通过对不同煤阶具体指标的分析并结合上述5类富集区的特点,提出了Ⅰ类目标区6个、Ⅱ类目标区5个、Ⅲ类目标区7个。其中沁水盆地南部晋城地区、鄂尔多斯盆地东南部吉县—韩城地区、准噶尔盆地东南部昌吉—大井地区是近期3个千亿立方米煤层气储量规模的有利区;Ⅱ类和Ⅲ类目标区将成为中国煤层气中长期发展的重要领域。

Occurrence features and exploration orientation of coalbed methane gas in China

There are rich coalbed methane (CBM) gas resources in China, featured by substantial coal bearing basins, various coal bearing formations and layers, full scale coal types, and numerous CBM gas reservoirs. The CBM reserves with a burial depth of less than 1000 m are up to 14.27 tcm, which becomes the main exploitation target. Under the current situation that China has unveiled some supporting policies, it is high time that we should speed up the CBM development through getting a full knowledge of CBM occurrence features, accurately selecting the CBM enrichment zones, and drilling with success at the target zones. According to the achievements in recent years, 5 major types of CBM enrichment zones are concluded as follows: structural high of some regional coal bearing areas, acclivity areas with an even distribution of direct sealing rocks, active volcanic areas in the structure of uplift in depression, developed areas with low rank coals and thick coal beds under good sealing conditions in the shallow formations, and a well developed secondary coal cleats areas formed in fault activities. There is a large potential in the CBM development which is still at initial stage in present China. Through concrete analysis on the indexes of different rank coals, in combination with the above mentioned 5 major CBM enrichment zones, we present 6 type I, 5 type Ⅱ, and 7 type Ⅲ target zones, among which the latter two types will be the important areas for the middle and long term CBM development in China; the former one is represented by three large commercial scale CBM zones with 300 bcm reserves including the Jincheng district in the southern Qinshui Basin, the Jixian Hancheng district in the southeastern Ordos Basin, and Changji Dajin district in the southeastern Jungar Basin.