川南煤田古叙矿区DC-5井上二叠统龙潭组煤层甲烷吸附性及其主控因素

Constraints of methane absorbability in the Upper Permian Longtan Formation of Well DC-5 in Guxu mine area of southern Sichuan Coalfield

煤层甲烷吸附性研究对于指导煤层气勘探开发以及揭示煤层储气机理具有重要作用。通过钻井取样、煤岩-煤质特性分析以及甲烷等温吸附实验,研究了川南煤田古叙矿区龙潭组不同深度煤层的煤质特征与甲烷吸附性差异,运用多元线性逐步回归方法分析了影响煤层甲烷吸附能力的主要因素。结果表明:古叙矿区龙潭组煤镜质组最大反射率RO,max值为2.83%~3.22%,属于高阶煤;显微组分以镜质组为主,惰质组次之,不含壳质组,无机矿物以黏土类为主;不同煤层的水分含量和挥发份产率差别不大,但是灰分产率和固定碳含量差别较大,导致朗格缪尔体积变化在11.39~25.06 m^3/t之间。认为固定碳含量是影响古叙矿区煤层甲烷吸附能力的主要因素,且固定碳含量与朗格缪尔体积呈正相关关系。

Research on the absorbability of coalbed methane is of importance for guiding the exploration and exploitation of coalbed methane and revealing the storage mechanism of coalbed methane. This study investigates the coal quality and methane adsorption capacity at different depth of the Longtan Formation in the Guxu mine area of southern Sichuan Coalfield by drilling sampling,coal rock and coal analysis,and methane isothermal adsorption testing. The main geological factors affecting methane adsorption capacity are analyzed using a multiple linear stepwise regression method. Results show that the coal rank of the Longtan Formation in the Guxu mine area has reached the anthracite stage(Ro,max ranges from 2.83% to 3.22%),which belongs to high-rank coals.Vitrinite is the main component of coal maceral and followed by inertinite without exinite. Clay mineral is the main component of the inorganic mineral. The difference of moisture and volatile matter contents between coal seams in the Longtan Formation is small,while a large difference between ash and fixed carbon contents is observed. Langmuir volume(VL)of different coal seams ranges from 11.39 to 25.06 m^3/t. Fixed carbon content is the main factor affecting the methane adsorption capacity of the coal seams in the Guxu mine area. The content of fixed carbon is positively correlated with the methane adsorption quantity.