ABSTRACT Taking insight into genetic mechanisms of coalbed methane (CBM) can provide an effective approach for evaluating the value of CBM resources. In this study, the geo-temperature and the thermal subsidence history were used to investigate the effect of the present geothermal field characteristic on the genetic mechanisms of CBM at the Huaibei Coalfield. The results showed that the Permian coal strata in the study areas had a relatively low geo-temperature (< 50°C), high vitrinite reflectance (Ro,max; 0.75%-1.2%) and a coal rank typical of intermediate-high metamorphic bituminous. Comprehensive analyses of the characteristics of the present geothermal field indicate that the CBM at the Huaibei Coalfield are dominated by secondary biogenic gases. Furthermore, the genetic mechanism towards CBM was further proposed based on the tectonic evolution history: (1) Tectonic thrusting contributed to Ro,max values ranging from 0.5% to 3.0%, with maximum geo-temperatures of 140–180°C, which resulted in the generation of thermogenic CBM. (2) An extensional regime contributed to gradual uplift of the Permian coal-bearing strata, with the gradual escape of CBM at burial depths greater than 700m. (3) A large number of faults and hydrodynamic environments greatly promoted the microbial degradation of the early thermogenic gases, resulting in generation of secondary biogenic gases.

中文翻译：

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华东淮北煤田典型区煤层气成因机制

摘要 深入了解煤层气（CBM）的成因机制可以为评估煤层气资源的价值提供一种有效的方法。本研究利用地温和热沉降史研究了当前地温场特征对淮北煤田煤层气成因机制的影响。结果表明，研究区二叠纪煤层地温较低（<50℃），镜质体反射率较高（Ro,max；0.75%-1.2%），煤阶为典型的中高变质煤层。沥青。综合分析现今地热田特征，淮北煤田煤层气以次生生物气为主。此外，基于构造演化历史进一步提出了煤层气的成因机制：(1) 构造推力对 Ro 的贡献，最大值范围为 0.5% 至 3.0%，最高地温为 140-180°C，导致产热煤层气。(2) 伸展体制促使二叠系含煤地层逐渐抬升，煤层气在埋深大于700m处逐渐逸出。(3)大量断层和水动力环境极大地促进了早期热成因气体的微生物降解，导致次生生物成因气体的生成。(2) 伸展体制促使二叠系含煤地层逐渐抬升，煤层气在埋深大于700m处逐渐逸出。(3)大量断层和水动力环境极大地促进了早期热成因气体的微生物降解，导致次生生物成因气体的生成。(2) 伸展体制促使二叠系含煤地层逐渐抬升，煤层气在埋深大于700m处逐渐逸出。(3)大量断层和水动力环境极大地促进了早期热成因气体的微生物降解，导致次生生物成因气体的生成。