鄂尔多斯盆地彬县—长武地区低煤阶煤层气成藏特点

Reservoir forming characters of low-rank CBM in Binchang block, Ordos basin

鄂尔多斯盆地彬县—长武地区(以下称"彬长地区")的低煤阶煤层气资源量丰富,勘查程度较高。与高煤阶煤层气成藏特征相比,低煤阶由于热演化程度较低,生气量受到构造演化史、沉积相的限制,同时保存条件影响了煤层气成藏。阐述了彬长地区低煤阶煤层气基本地质条件,并且从构造、沉积和水动力条件三个方面分析了低煤阶煤层气成藏特点。通过研究认为侏罗系延安组8号煤是彬长区块的主要目标层位,而且厚度较大,渗透性较好,尤其是研究区中南部的8号煤层又具有有利的盖层条件,是煤层气的富集区。

Binchang block of Ordos basin has abundant low-rank coalbed methane （CBM） and high exploration degree. Because of low thermal evolution degree, compared with forming characters of high-rank CBM, gas generation content of low-rank CBM is restricted by structural evolution history and sedimentary facies. Meanwhile, preservation conditions affect CBM accumulation. This paper described the basic geological condition of low-rank CBM in Binchang block and analyzed its forming characters from three aspects, such as structural environment, deposition condition and hydrodynamic condition. The research shows that No.8 coalbed of Jurassic Yan＇ an formation is the main target stratigraphic position. Having the advantages of large coalbed thickness and high permeability, especially No.8 coalbed possessing favorable conditions of forming capping formation, it is the enrichment region of CBM.