Abstract The micro-occurrence and utilization patterns of coalbed methane and shale gas are complex, which has limited their scientific explorations and exploitation. Based on high-temperature/high-pressure nuclear magnetic resonance (NMR) online detection technology, a T2 cut-off calibration method for adsorbed, pore-confined and free gas was established. The “one-point calibration method” for the NMR T2 cut-off value of the adsorbed gas was established by combining conventional isothermal adsorption and NMR technology, which substantially facilitated and simplified engineering applications. Based on the calibration of T2 cut-off values for different states, the variations in coalbed methane or shale gas under different occurrence states and the impact of this variation on gas production was quantitatively evaluated during production. Coalbed rock samples from the East Mabi block of the Qinshui Basin, Shanxi Province were used to study the aforementioned method. This study shows that approximately 90% of the coalbed methane is in an adsorbed state, and the proportion of adsorbed methane is slightly lower if the samples contain water. In addition, adsorbed gas is the main source of coalbed methane production, followed by pore-confined gas, with only a small contribution from free gas. Approximately 70% of the gas produced from dry coal samples comes from adsorbed gas, and approximately 60% of the gas produced from wet coal samples comes from adsorbed gas. The contribution of pore-confined gas to production is approximately 20%, regardless of the difference in the water content of the samples. At different development stages, different occurrence states vary significantly in their contribution to drainage and recovery. In the early stage, production is mainly from pore-confined gas and free gas, while in the later stage, it is mainly from adsorbed gas. As production proceeds, the output gradually increases. If pressure drops to a certain value, the output gradually decreases, and maximum production is achieved at approximately 3 MPa. This article lays the foundation for more economical and effective exploitation of coalbed methane and shale gas.

中文翻译：

---

一种基于核磁共振的新方法评价瓦斯微量发生和利用模式

摘要 煤层气和页岩气的微观赋存和利用模式复杂，限制了其科学勘探和开发。基于高温/高压核磁共振（NMR）在线检测技术，建立了吸附气、孔隙约束气和游离气的T2截止标定方法。结合常规等温吸附和核磁共振技术，建立了吸附气体核磁共振T2临界值的“单点校准法”，极大地方便和简化了工程应用。基于对不同状态T2临界值的标定，在生产过程中定量评价了不同赋​​存状态下煤层气或页岩气的变化及其对产气量的影响。采用山西省沁水盆地东马壁区块煤层岩样品对上述方法进行研究。本研究表明，约90%的煤层气处于吸附状态，如果样品含水，吸附的甲烷比例略低。此外，吸附气是煤层气生产的主要来源，孔隙气次之，游离气贡献较小。干煤样产气约70%来自吸附气，湿煤样产气约60%来自吸附气。孔隙受限气对产量的贡献约为 20%，无论样品的含水量如何差异。在不同的发展阶段，不同的发生状态对排水和采收的贡献差异很大。前期以孔隙封闭气和游离气为主，后期以吸附气为主。随着生产的进行，产量逐渐增加。如果压力下降到一定值，产量会逐渐降低，大约在 3 MPa 时达到最大产量。本文为更经济有效地开发煤层气和页岩气奠定了基础。在大约 3 MPa 时达到最大产量。本文为更经济有效地开发煤层气和页岩气奠定了基础。在大约 3 MPa 时达到最大产量。本文为更经济有效地开发煤层气和页岩气奠定了基础。