Evolution of Production and Transport Characteristics of Steeply-Dipping Ultra-Thick Coalbed Methane Reservoirs

Shun Liang, Hao Han, Derek Elsworth, Xuehai Fu, Qiangling Yao, Junqiang Kang, Xin Li and Xuehua Li
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Shun Liang: State Key Laboratory of Coal Resource and Mine Safety, School of Mines, China University of Mining and Technology, Xuzhou 221008, China
Hao Han: State Key Laboratory of Coal Resource and Mine Safety, School of Mines, China University of Mining and Technology, Xuzhou 221008, China
Derek Elsworth: EMS Energy Institute, G3 Center and Energy and Mineral Engineering, Pennsylvania State University, University Park, PA 16802, USA
Xuehai Fu: Key Laboratory of CBM Resources and Reservoir Formation Process, Ministry of Education, China University of Mining and Technology, Xuzhou 221008, China
Qiangling Yao: State Key Laboratory of Coal Resource and Mine Safety, School of Mines, China University of Mining and Technology, Xuzhou 221008, China
Junqiang Kang: EMS Energy Institute, G3 Center and Energy and Mineral Engineering, Pennsylvania State University, University Park, PA 16802, USA
Xin Li: School of Geology and Mining Engineering, Xinjiang University, Urumchi 830047, China
Xuehua Li: State Key Laboratory of Coal Resource and Mine Safety, School of Mines, China University of Mining and Technology, Xuzhou 221008, China

Energies, 2020, vol. 13, issue 19, 1-25

Abstract: The large spatial variability of in-situ stress and initial reservoir pressure in steeply-dipping ultra-thick coalbed methane (UTCBM) reservoirs exert strong control on the initial distribution of stress-sensitive permeability. This results in significant differences in the propagation of reservoir depressurization, gas production characteristics, distribution of fluid saturation, and evolution of permeability relative to flat-lying and thin counterpart coalbed methane (CBM) reservoirs. We contrast these responses using the Fukang mining area of the Junggar Basin, Xinjiang, China, as a type-example using coupled hydro-mechanical modeling. Production response indicates: (1) Dual peaks in CBM production rate, due to the asynchronous changes in the gas production rate in each the upper and lower sections of the reservoir; (2) higher depressurization and water saturation levels in the lower section of the reservoir relative to the upper at any given distance from the production well that ameliorate with time to be similar to those of standard horizontal reservoirs; (3) the heterogeneity in effective stress is further amplified by the asymmetry of the initial pressure drawdown distribution of the reservoir to exert extreme control on the down-dip evolution of absolute permeability—with implications for production. Field drainage data and simulation results obtained in this study more accurately reflect the drainage characteristics of the steeply-dipping UTCBM reservoirs. For ultra-thick low-rank coal seams, permeability anisotropy plays an important role in determining the utility of horizontal wells and hydraulic fracturing to maximize rates and yields CBM production, and requiring further study.

Keywords: large dip angle; ultra-thick; coalbed methane; dual peak production; anisotropic permeability; stress heterogeneity (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: 2020
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