韩城矿区中高阶煤储层煤层气可解吸性及其影响因素研究

CBM desorption property and geological controls of middle-high rank coal reservoirs in Hancheng Mining Area

以韩城矿区煤心解吸数据为基础,分析了中高阶煤储层中煤层气解吸特征及规律,探讨了解吸特征与煤的变质程度、显微组分、工业组分等之间的关系。结果表明:研究区煤层气可解吸率介于13%~72%之间,5号煤层解吸速度最大;煤层气解吸具有阶段性,解吸速度的降低主要由煤储层含气量的变化引起,初始解吸速度及其衰减特征与煤岩孔隙结构及其连通性有关;可解吸率在区域上受埋深的影响,数据较为离散;可解吸率与煤变质程度相关性不明显,但随灰分产率增加而显著降低,随水分含量增加显著升高;镜质组含量的增加可以提高煤层气解吸率,而惰质组则相反。薛峰地区的5号煤层和11号煤层、王峰南部和魏东西部的5号煤层、魏东南部的11号煤层可解吸率较高,均大于50%,有利于煤层气的开发。

Based on the desorption data of coal cores in Hancheng mining area, we analyzed the characteristics and laws of coalbed gas desorption in high rank coal reservoir; then studied the relationship between the characteristics of absorption and coal metamorphism, maceral and industrial classification. The results show that the desorption rate of combed methane in the study area is between 13%- 72%, the desorption rate of No. 5 coal is the largest. The desorption of coalhed methane is of stage character, and the decrease of desorption rate is mainly caused by the change of gas content in coal reservoirs. The initial desorption rate and its attenuation characteristics are related to pore structure and coal-rock connectivity. The influence of desorption rate in the area is more complex, which the data is more discrete. The desorption rate is not significantly correlated with the degree of coal metamorphism, which decreases with the increase of ash yield, and increases significantly with the increase of water content. Methane desorption rate increases with the increase of vitrinite content, while the content of vitrinite inertinite is on the contrary. The desorption rate of coal No. 5 and No. 11 coal in Xuefeng area, No. 5 coal in South of Wangfeng area and west of Weidong area, No. 11 coal in the southern part of Wei Dong area is higher, which is more than 50%, and conducive to the development of coal-bed methane.