Abstract This paper focusses on sequence stratigraphy of coal-bearing strata, coal petrography, coal chemistry, and the CH4 adsorption capacity of the Badaowan Formation in Santanghu Basin, China. The comprehensive coal characteristics of 12 coal samples were determined, coupled with maceral composition, proximate analysis, elemental analysis, reflectance (Ro), and high-pressure CH4 adsorption. The results indicated that maceral composition and chemical properties of coal were controlled by the sequence stratigraphic framework. During the TST, the content of vitrinite, the ratio of vitrinite to inertinite (V/I) and the content of carbon in coal increased gradually from bottom to top. While during HST, an opposite trend was observed. Furthermore, due to the intrusion of the lake water, the ash yield in the TST is higher than that in HST. The CH4 adsorption capacity is positively correlated with the content of vitrinite and V/I. There is a moderate positive correlation between fixed carbon contents and VLad. Ash content was strongly correlated to Langmuir volume under the air-dry basis, with increasing Ad associated with the reduction of the VLad. It was observed that the CH4 adsorption capacity generally gradually increased during the TST, and gradually decreased in the HST. Gas content also shows a similar change rule. CH4 adsorption capacity is functionally dependent on coal characteristics, which again are dependent on sequence stratigraphy and thus the coal-forming environment. The base level and cycles of the sequence establish a theoretical and practical framework for CBM extraction from low-rank coal reservoirs.

中文翻译：

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层序地层对三塘湖盆地低阶煤煤特性及CH4吸附能力的影响

摘要 本文对三塘湖盆地八道湾组含煤地层层序地层学、煤岩学、煤化学及CH4吸附能力进行了研究。结合微量成分、近似分析、元素分析、反射率(Ro)和高压CH4吸附，测定了12个煤样的综合煤特性。结果表明，煤的成分和化学性质受层序地层格架控制。TST期间，镜质体含量、镜质体与惰性体比（V/I）和煤中碳含量自下而上逐渐增加。而在 HST 期间，观察到了相反的趋势。此外，由于湖水的侵入，TST 的灰分产量高于 HST。CH4 吸附量与镜质体含量和 V/I 呈正相关。固定碳含量与 VLad 之间存在中度正相关。灰分含量与在风干基础上的朗缪尔体积密切相关，增加 Ad 与 VLad 的减少相关。观察到 CH4 吸附量在 TST 期间一般逐渐增加，在 HST 中逐渐降低。气体含量也显示出类似的变化规律。CH4 吸附能力在功能上取决于煤的特性，而煤的特性又取决于层序地层，因此也取决于成煤环境。该层序的基础水平和旋回为低阶煤储层煤层气的提取建立了理论和实践框架。