海孜井田岩浆侵入对下伏煤层的热变质作用研究

Thermal metamorphism effect of magma intrusion on underlying coal seams in the Haizi mine field

采用理论分析、数值模拟和实验室试验验证的方法,以岩浆作为侵入时期煤变质的主要热源,构建了岩浆侵入煤系地层后热传导作用的数学模型,结合研究区域煤样的多元物性参数测定结果,深入探讨了侵入岩浆对下伏煤层的热变质作用,揭示了海孜井田下伏煤层的演化生烃过程.结果表明:岩浆对围岩的高温作用持续时间相对比较短暂,随着侵入岩浆岩体厚度的增大,相同距离的围岩体在同一时刻达到的温度和最终达到的最高温度均增加,但达到最高温度的时间被延后.高温侵入岩浆冷却过程较低温侵入岩浆的冷却过程持续时间长,热影响范围大,且热力影响区域内同一点达到的最高温度也比低温侵入岩浆在该点产生的最高温度高.随着距岩浆岩距离的增加,煤层的最高有效温度和持续高温作用时间减少.海孜井田岩浆岩下伏煤层受岩浆热演化作用发生二次生烃,煤层变质程度显著增加,产烃量约为340 m^3/t.

Based on theoretical analysis, numerical simulation and laboratory test, the mathematical model of heat conduction after the magma intrusion into coal measures was built with magma as the main heat source of coal metamorphism. By determining the multiple physical parameters of coal samples from research area, the thermal metamorphism of intrusive magmatic on underlying coal seams was discussed, and the hydrocarbon generation process of the underlying coal seams in the Haizi mine field was studied. Results show that the duration of magma thermal effect on surrounding rock in high temperature is short; the temperature and the maximum temperature of rock mass with the same distance increase with the thickness of intrusive magmatic rock, whereas the time reaching maximum temperature is delayed; comparing with the intrusive magma with low initial temperature, the duration of cooling process of intrusive magma with high initial temperature is longer, and the area of thermal effects and the maximum temperature at the same point are larger; with the increasing distance from magmatic rockto coal seams, the maximum effective temperature and the duration of high temperature decrease. Secondary hydrocarbon generation occurs in the underlying coal seams of the Haizimine field due to thermal evolution, thedegree of coal metamorphism increases significantly, and the amount of hydrocarbon production is approximate 340 m^3/t.