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LAPSE:2023.15467v1

An NMR-Based Method for Multiphase Methane Characterization in Coals

Sijian Zheng, Shuxun Sang, Shiqi Liu, Xin Jin, Meng Wang, Shijian Lu, Guangjun Feng, Yi Yang, Jun Hou

March 2, 2023

Abstract
Discriminating multiphase methane (adsorbed and free phases) in coals is crucial for evaluating the optimal gas recovery strategies of coalbed methane (CBM) reservoirs. However, the existing volumetric-based adsorption isotherm method only provides the final methane adsorption result, limiting real-time dynamic characterization of multiphase methane in the methane adsorption process. In this study, via self-designed nuclear magnetic resonance (NMR) isotherm adsorption experiments, we present a new method to evaluate the dynamic multiphase methane changes in coals. The results indicate that the T2 distributions of methane in coals involve three different peaks, labeled as P1 (T2 < 8 ms), P2 (T2 = 20−300 ms), and P3 (T2 > 300 ms) peaks, corresponding to the adsorbed phase methane, free phase methane between particles, and free phase methane in the sample cell, respectively. The methane adsorption Langmuir volumes calculated from the conventional volumetric-based method qualitatively agree with those obtained from the NMR method, within an allowable limit of approximately ~6.0%. Real-time dynamic characterizations of adsorbed methane show two different adsorption rates: an initial rapid adsorption of methane followed by a long stable state. It can be concluded that the NMR technique can be applied not only for methane adsorption capacity determination, but also for dynamic monitoring of multiphase methane in different experimental situations, such as methane adsorption/desorption and CO2-enhanced CBM.

Record ID

LAPSE:2023.15467v1

Keywords

Coal, free methane, low-field NMR, paramagnetic mineral

Subject

Materials

Suggested Citation

Zheng S, Sang S, Liu S, Jin X, Wang M, Lu S, Feng G, Yang Y, Hou J. An NMR-Based Method for Multiphase Methane Characterization in Coals. (2023). LAPSE:2023.15467v1

Author Affiliations

Zheng S: Carbon Neutrality Institute, China University of Mining and Technology, Xuzhou 221008, China; The Key Laboratory of Coal-Based CO2 Capture and Geological Storage, China University of Mining and Technology, Xuzhou 221116, China
Sang S: Carbon Neutrality Institute, China University of Mining and Technology, Xuzhou 221008, China; The Key Laboratory of Coal-Based CO2 Capture and Geological Storage, China University of Mining and Technology, Xuzhou 221116, China; School of Resources and Geo [ORCID]
Liu S: Carbon Neutrality Institute, China University of Mining and Technology, Xuzhou 221008, China; The Key Laboratory of Coal-Based CO2 Capture and Geological Storage, China University of Mining and Technology, Xuzhou 221116, China
Jin X: Xi’an Research Institute, China Coal Technology and Engineering Group, Xi’an 710077, China; Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring, Ministry of Education, School of Geosciences and Info-Phy
Wang M: Carbon Neutrality Institute, China University of Mining and Technology, Xuzhou 221008, China; The Key Laboratory of Coal-Based CO2 Capture and Geological Storage, China University of Mining and Technology, Xuzhou 221116, China
Lu S: Carbon Neutrality Institute, China University of Mining and Technology, Xuzhou 221008, China; The Key Laboratory of Coal-Based CO2 Capture and Geological Storage, China University of Mining and Technology, Xuzhou 221116, China
Feng G: School of Resources and Geosciences, China University of Mining and Technology, Xuzhou 221116, China
Yang Y: Xi’an Research Institute, China Coal Technology and Engineering Group, Xi’an 710077, China
Hou J: College of Civil Engineering, Anhui Jianzhu University, Hefei 230601, China

Journal Name

Energies

Volume

Issue

First Page

1532

Year

2022

Publication Date

2022-02-18

DOI:

https://doi.org/10.3390/en15041532