新疆巴里坤矿区煤层气赋存规律及控气地质因素

Coalbed Methane Occurrence Regularity and Geological Factors of Controlling Gas in Xinjiang Balikun Mining Area

新疆巴里坤矿区唯一含煤地层为下侏罗统八道湾组(J1b),根据煤层赋存状态可分为西区、中区与东区,通过对矿区大量钻孔数据和生产矿井实测资料的综合分析,基本查明矿区煤层气赋存状态为水平方向上从西到东呈阶梯状增长、垂直方向上随煤层埋深呈线性增长的赋存规律。矿区煤层气赋存受多种控气地质因素共同作用:稳定的沉积环境有利于成煤聚煤,为煤层气的生成提供了原始条件;后期的构造运动导致西部矿区煤层抬升露头,中东部矿区逆冲、压扭性断层发育,断层面的封闭性与构造煤的透气性共同导致煤层气在近断层处的应力集中带聚集形成气顶;地下水对游离态煤层气形成有效封堵,且随着煤层埋深煤层含气量有显著增大的趋势。上述控气地质因素共同造成巴里坤矿区煤层气赋存呈现西部逸散、中东部富集形成水力封堵-断层型煤层气藏。

Badaowan Formation of Jurassic is the only one coal-bearing stratum of Balikun mining area in Xinjiang. According to the coal seam occurrence,the coal deposit can be divided into the west, central and east zones. The comprehensive analysis of a large number drilling data and measured data of producing mines in mining area reveals that the occurrence of coalbed methane of mining area is with the occurrence regularity of the horizontal direction from west to east in ladder shaped growth and vertical direction with the depth of coal seam in linear growth. Coalbed methane occurrence of the mining area is formed by vari- ous geological factors controlling gas formation. Stable sedimentary environment is helpful for coal accu- mulation, providing the original conditions for the production of coalbed methane. The late tectonic move ment in western mining that lifted the outcrop of coal seam, the thrust and pressure shear fault developed in the middle and east mining area, closeness fault surface and permeability tectonic coal are the main cau- ses for coalbed methane gathering to form gas cap nearby the stress concentration belt of geological faults. Groundwater for free CBM effectively suppressed, with the buried depth of coal seam gas content of coal seam tending to increase significantly. The above geological factors control the formation of gas jointly and cause the Balikun mining area eoalbed methane occurrence to present western dissipation, enrichment of east-central CBM reservoir hydraulic seal-fault pattern.