Accurate quantification of the coexistence of adsorbed and free gas content holds the utmost significance for estimating gas-in-place resources and predicting gas production dynamics. In this study, we conducted real-time isothermal adsorption experiments and NMR fluid monitoring on stress-confining core samples, from the Zhengzhuang Block's No.3 coal seam in the southern Qinshui Basin. Our focus was on assessing multi-phase methane gas contents within coal under various pressure and temperature (P/T) conditions. By integrating experimental findings with adsorption potential theory and the SDR adsorption model, we developed comprehensive models for adsorbed, free, and total gas contents as functions of P/T and water/gas volume saturation. Utilizing these models, we predicted vertical variations in adsorbed and free gas contents within the coal seam. Our results revealed that the interplay between positive reservoir pressure effects and adverse reservoir temperature effects influenced both adsorbed and free methane gases. With increasing burial depth, the influence of pressure on adsorbed gas diminished, while temperature effects became more pronounced. Conversely, free gas content responded noticeably to reservoir pressure, with temperature exerting a marginal influence. Additionally, we performed a numerical simulation to reconstruct the thermal history, burial trajectory, and evolution of reservoir pressure for the No.3 coal seam. The simulation results served as foundational data for understanding the evolution of free and adsorbed gas contents across different geological epochs within the in-situ reservoir. Our findings unveiled a four-stage evolutionary progression in both adsorbed and free gas contents, correlating with the uplift and subsidence of the coal seam. In conclusion, our study provides a conceptual model elucidating the intricate, deep-time evolution process and mechanisms governing the occurrence of multiphase gases across distinct geological epochs. The implications of this research are crucial for accurately evaluating gas-in-place resources and guiding the exploration and development of deep coalbed methane resources.

中文翻译：

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深层煤层中原位吸附/游离气体演化的定量表征：核磁共振流体检测和地质时间模拟的见解

准确量化吸附气和游离气含量的共存对于估算天然气地质资源量和预测天然气产量动态具有重要意义。在本研究中，我们对沁水盆地南部郑庄区块3号煤层的应力约束岩心样品进行了实时等温吸附实验和核磁共振流体监测。我们的重点是评估不同压力和温度 (P/T) 条件下煤中的多相甲烷气体含量。通过将实验结果与吸附势理论和 SDR 吸附模型相结合，我们开发了吸附气体、游离气体和总气体含量作为 P/T 和水/气体体积饱和度函数的综合模型。利用这些模型，我们预测了煤层内吸附瓦斯和游离瓦斯含量的垂直变化。我们的结果表明，正的储层压力效应和不利的储层温度效应之间的相互作用影响了吸附甲烷气体和游离甲烷气体。随着埋深的增加，压力对吸附气体的影响逐渐减弱，而温度的影响则变得更加明显。相反，游离气含量对储层压力的响应显着，而温度的影响很小。此外，我们还进行了数值模拟，重建了 3 号煤层的热历史、埋藏轨迹和储层压力演化。模拟结果为了解原位储层不同地质时期游离气和吸附气含量的演变提供了基础数据。我们的研究结果揭示了吸附瓦斯含量和游离瓦斯含量的四阶段演化进程，与煤层的隆起和沉降相关。总之，我们的研究提供了一个概念模型，阐明了复杂的深层演化过程和控制不同地质时期多相气体出现的机制。该研究对于准确评价天然气地质资源量、指导深层煤层气资源勘探开发具有重要意义。