岩浆热事件对煤层变质程度和吸附-解吸特性的影响

为研究岩浆侵入热事件对煤层变质程度和吸附-解吸特性的作用机制,采用理论分析、实验室测定和现场验证的方法,对比分析了淮北矿区海孜井田岩浆岩侵入区和邻近临涣井田未受岩浆影响的煤层多元物性参数变化规律和孔隙特征,系统研究了采集煤样的等温吸附与吸附平衡条件下瓦斯解吸过程,揭示了岩浆岩床下伏煤层瓦斯赋存特征。结果表明:海孜井田岩浆热演化作用使煤层变质程度显著增加,煤层挥发分降低,岩浆岩覆盖区域煤层的最大镜质组反射率梯度为0.53%/100 m,远大于深成变质作用。岩浆热演化区孔径0.4~0.7 nm之间的微孔极为发育,其发育程度是未受岩浆岩覆盖区煤样的数倍,且越靠近岩浆岩的煤层,微孔发育程度越明显。岩浆热演化区内煤体的吸附能力增强,吸附瓦斯量增大,煤体的瓦斯放散初速度变大,初期解吸速度快且解吸总量大。由于岩浆岩床对下伏煤层的热变质和封存作用,易造成下伏各煤层的瓦斯压力和瓦斯含量增高,煤层的突出危险性增加。

Influence of thermal events of magma intrusion on coal seams metamorphic grade and adsorption and desorption characteristics

In order to research the influence of thermal events of magma intrusion on coal seams metamorphic grade and adsorption-desorption characteristics，based on theoretical analysis，laboratory testing and field verification，the author compared and analyzed multiple physical parameters testing results and pore characteristics of coal samples collected from the Haizi mine field covered by magmatic rock and the Linhuan mine field without magma intrusion in the Huaibei mining area.The coal samples isothermal adsorption process and gas desorption process under adsorption equilibrium pressure were systematically studied，and gas occurrence characteristics of underlying coal seams were revealed.The results show that the metamorphic grade of coal seam increases significantly in magma thermal evolution area，and the coal maximum vitrinite reflectance gradient is 0.53%/100 m under magmatic rock which is far larger than on the coal original metamorphism affected by the burial depth.Microspores between 0.4-0.7 nm in diameter are extremely developed in the thermal evolution area which is more obvious when gets closer the magmatic rocks，and microspore development degree is several times larger than that in area without magmatic rock covering.In the thermal evolution area，coal adsorption ability is enhanced，the amount of adsorbed gas and coal gas emission initial velocity are enlarged，and initial desorption speed and desorption amount increase.Under the thermal metamorphism and sealing effect of magmatic rock，gas pressure and gas content of underlying coal seams become higher which increase coal and gas outburst risk.