Study of the Microstructural Characteristics of Low-Rank Coal under Different Degassing Pressures

Yuanzhen Ma, Meng Wang, Xinzhuo Zhao, Xuguang Dai and Ye He
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Yuanzhen Ma: Key Laboratory of Coalbed Methane Resources and Reservoir Formation Process, Ministry of Education, Xuzhou 221008, China
Meng Wang: Key Laboratory of Coalbed Methane Resources and Reservoir Formation Process, Ministry of Education, Xuzhou 221008, China
Xinzhuo Zhao: The Fifth Institute of Geology and Mineral Exploration of Shandong Province, Tai’an 271099, China
Xuguang Dai: Key Laboratory of Coalbed Methane Resources and Reservoir Formation Process, Ministry of Education, Xuzhou 221008, China
Ye He: Xuzhou Coal Mining Group, Xuzhou 221008, China

Energies, 2022, vol. 15, issue 10, 1-14

Abstract: Low-rank coal samples from the Xishanyao Formation in the southern Junggar basin of Xinjiang were processed under different negative pressures in order to examine the microstructural characteristics of low-rank coal reservoirs. The pore structures of low-rank coal under different negative pressures were tested using scanning electron microscopy, low-temperature nitrogen adsorption–desorption, and water saturation and centrifugal low-field NMR experiments. The results showed that for the low-rank coal samples from the study area, a high portion of the porosity and surface area came from micropores and small pores; the fractal dimension of the adsorption pores of the low-rank coal samples was divided into surface fractal dimension D 1 and structural fractal dimension D 2 , which showed that the microstructure of the low-rank coal from the study area was complex. The transverse relaxation times T 2 of the low-rank coal samples in the test were approximately 0.1~2.5, approximately 10, and greater than 100 ms; the T 2 spectrum had basically three peak types. By combining scanning electron microscopy and nuclear magnetic resonance tests, it was concluded that the pore connectivity of the low-rank coal reservoirs in the study area was poor and the effective porosity was relatively low, which may be unfavorable for the exploration and development of coalbed methane.

Keywords: low-rank coal; microstructure; southern Junggar basin; Xishanyao Formation; nuclear magnetic resonance (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2022
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