鄂尔多斯盆地乌审旗地区煤层气富集主控因素及其勘探方向

乌审旗地区是鄂尔多斯盆地的重要含煤区，也是近几年低煤阶煤层气勘探的热点地区。但该区前期煤层气钻探总体效果并不理想，迫切需要认清该区煤层气富集规律，以便有效开展煤层气勘探及开发利用。为此，对该区煤层分布特征、聚煤期沉积环境、煤岩特征及储层物性、煤层含气性等地质条件进行了分析，发现该区煤岩演化程度低，以低煤阶长焰煤为主，煤层厚5~30 m，大部分地区煤层埋深小于1 000 m且分布稳定，具有一定的煤层气勘探潜力。但煤层气钻井揭示该区煤层含气性变化大，煤层含气量介于0.19～6.7 m³/t，部分地区煤层气组成中CH₄含量小于25%，说明煤层早期成岩时生成吸附的甲烷已被破坏逸散。进一步分析影响该区煤层气富集的主控因素后认为：在煤层直接盖层为砂岩、保存条件差的地区，煤层含气性差，反之，则含气性好，如果有后期生物气的补充，则可以富集成藏。最后指出：该区北部的乌审召区块和南部的纳林河区块，煤层气保存条件好、含气量高、勘探潜力大，可作为下一步煤层气勘探的有利目标区。

Controlling factors of coalbed methane enrichment in the Wushenqi Area,Ordos Basin

The Jurassic coal seams in the Ordos Basin are rich in low-rank coalbed methane resources which is about 5.28 trillion m3 and accounts for 36% of the total low-rank coalbed methane resources(14.7 trillion m3) in China.Wushenqi,an important Jurassic coal-bearing area in the Ordos Basin,is also the focus of low-rank coalbed methane gas exploration in recent years.Although many projects of coalbed methane gas drilling and exploration in this area have been substantially performed by the PetroChina,local govern...