山西保德中低阶煤层气地质特征

Geological characteristics of middle and low rank coalbed methane in Baode county of Shanxi Province

通过对钻井岩心及地化进行分析,揭示了山西保德地区煤层气地质特征。山西保德煤层厚度较大(5~10 m),埋藏较浅(450~700 m),为高发热量低阶煤层(30.98 MJ/kg)。其分布稳定,有机质成分高(60.2%~92.7%),变质程度低(Ro为0.55%~0.88%),硫含量较低0.24%~1.73%,应用安全性较高,抗碎强度大(80.1%~86.0%),不易破碎,便于压裂开采。煤层孔隙度大、渗透率高,易形成游离气的运移和聚集。煤层地处地下水径流区,地下水渗流具有侧向封堵性能,封闭性的逆断层对煤层气也具有良好的封堵作用。其构造简单,顶底板均为砂质泥岩与泥岩,封堵条件好。实验室测试,煤层吸附能力很强(3.79~14.27 m^3/t),并随埋深增强。其含气饱和度较大(10.67%~85.94%),具有随埋深增强的趋势。储层压力较大(2.09~2.96 MPa),具有富集成藏的良好条件。实践开采显示,8煤层含气量为0.48~7.856 m^3/t,自上而下逐步增大,且甲烷含量高(18.29%~95.47%);11煤层含气量为0.44~4.67 m^3/t,自上而下逐步增加,甲烷含量高(1.24%~93.29%)。目前2层合并开采后稳定日产3 000 m^3,具有工业开采价值,可在该区加大勘探开发力度。

Through drilling core and geochemical analysis,the geological characteristics of coalbed methane are revealed in Baode county of Shanxi Province.The thickness of coal in Baode county of Shanxi Province is large(5~10 m),and the burial depth is relatively shallow(450~700 m),which is a high calorific and low rank coal(3 0.98 M J/kg).It is stable distribution,which has high organic matter composition(60.2%~92.7%),low degree of metamorphism(/~o=0.55%~0.88%),lower sulfur content from 0.24%to 1.7 3%,with high safety,and high crushing strength(8 0.1%~86%),so it is not easy to break and easy to fracture mining.The coal seam has large porosity and high permeability,which is easy to form migration and accumulation of free gas.The coal seam is located in water runoff zone,in which the groundwater seepage has the lateral sealing performance,and the sealing reverse fault also has a good plugging effect on the coalbed methane.Its structure is sim ple,the roof and bottom are all sand mudstone and mudstone,and the plugging condition is good.The laboratory test shows that the coal seam has a strong adsorption capacity(3.79~14.27 m3/t)and it increases with the buried depth.Its gas saturation is large(10.67%~85.94%),and has a tendency to increase with the buried depth.The reservoir pressure is large(2.09~2.96 M P a),and it has good conditions for accumulation and accumulation.The mining practice shows that 8 coal seam gas content is 0.480~7.856 m3/t,which has gradually increased from roof to bottom,and it has high methane content(18.29%~95.47%).11 coal seam gas content is 0.44~4.67 m3/t,which has gradually increased from roof to bottom and it has high methane content(l.24%~9 3.29%).At present,the mining of the two layers are merged together,which has stable 3 000 m3 every day.It has industrial mining value,so we can increase exploration and development efforts in the area.