A preliminary study of pressure-preserved coring calculation principle and method for in-situ pressure in deep coal seams

Authors

CUI Pengfei, State Key Laboratory of Intelligent Construction and Healthy Operation and Maintenance of Deep Underground Engineering, Guangdong Provincial Key Laboratory of Deep Earth Sciences and Geothermal Energy Exploitation and Utilization, Institute of Deep Earth Sciences & Green Energy, Shenzhen University, Shenzhen 518060, ChinaFollow
GAO Mingzhong, State Key Laboratory of Intelligent Construction and Healthy Operation and Maintenance of Deep Underground Engineering, Guangdong Provincial Key Laboratory of Deep Earth Sciences and Geothermal Energy Exploitation and Utilization, Institute of Deep Earth Sciences & Green Energy, Shenzhen University, Shenzhen 518060, China; State Key Laboratory of Hydraulics and Mountain River Engineering, College of Water Resource and Hydropower, Sichuan University, Chengdu 610065, ChinaFollow
SHANG Delei, State Key Laboratory of Intelligent Construction and Healthy Operation and Maintenance of Deep Underground Engineering, Guangdong Provincial Key Laboratory of Deep Earth Sciences and Geothermal Energy Exploitation and Utilization, Institute of Deep Earth Sciences & Green Energy, Shenzhen University, Shenzhen 518060, China
LI Jianhua, State Key Laboratory of Intelligent Construction and Healthy Operation and Maintenance of Deep Underground Engineering, Guangdong Provincial Key Laboratory of Deep Earth Sciences and Geothermal Energy Exploitation and Utilization, Institute of Deep Earth Sciences & Green Energy, Shenzhen University, Shenzhen 518060, China
CHU Peng, State Key Laboratory of Intelligent Construction and Healthy Operation and Maintenance of Deep Underground Engineering, Guangdong Provincial Key Laboratory of Deep Earth Sciences and Geothermal Energy Exploitation and Utilization, Institute of Deep Earth Sciences & Green Energy, Shenzhen University, Shenzhen 518060, China
SONG Jie, State Key Laboratory of Intelligent Construction and Healthy Operation and Maintenance of Deep Underground Engineering, Guangdong Provincial Key Laboratory of Deep Earth Sciences and Geothermal Energy Exploitation and Utilization, Institute of Deep Earth Sciences & Green Energy, Shenzhen University, Shenzhen 518060, China
LI Yongcheng, State Key Laboratory of Intelligent Construction and Healthy Operation and Maintenance of Deep Underground Engineering, Guangdong Provincial Key Laboratory of Deep Earth Sciences and Geothermal Energy Exploitation and Utilization, Institute of Deep Earth Sciences & Green Energy, Shenzhen University, Shenzhen 518060, China
HAO Haichun, State Key Laboratory of Intelligent Construction and Healthy Operation and Maintenance of Deep Underground Engineering, Guangdong Provincial Key Laboratory of Deep Earth Sciences and Geothermal Energy Exploitation and Utilization, Institute of Deep Earth Sciences & Green Energy, Shenzhen University, Shenzhen 518060, China

Abstract

The accurate acquisition of in-situ gas pressure in coal seams is a key link in the chain of the prevention and control of gas disasters. Presently, it is still necessary to explore accurate, low-cost, and time-saving methods for determining gas pressure. Based on the in-situ pressure-preserved coring for deep coal seams, this study proposed a calculation method for in-situ gas pressure in deep coal seams and developed the calculation process. Using the constructed numerical model of the gas pressure evolution in the pressure-preserved space, this study verified the reliability of the proposed method by comparison with the theoretical and numerical simulation results. Accordingly, this study further explored the evolutionary pattern of the gas pressure in the pressure-preserved space under different in-situ gas pressures in coal seams. The results indicate that (1) the indicated value of gas pressure in the pressure-preserved space is not the in-situ gas pressure in coal seams. When the indicated value was 0.3 MPa, the in-situ gas pressure of coal seams was about 0.38 MPa; (2) a higher gas pressure after equilibrium in the pressure-preserved space corresponds to a higher proportion of in-situ free gas and a higher proportion of the mass of free gas after equilibrium; (3) with the conversion of gas in the pressure-preserved space from the in-situ state to a new equilibrium state, the proportion of the mass of free gas increases gradually, while that of the mass of adsorbed gas decreases correspondingly; (4) after coring, the gas pressure in the pressure-preserved space evolves from rapid increase to slow increase and then to equilibrium since the pressure of the adsorbed gas in the matrix decreases slowly while the pressure of free gas decreases rapidly; (5) a higher permeability of coal cores corresponds to a shorter time required for the gas pressure in the pressure-preserved space to reach equilibrium. However, the final gas pressure in the pressure-preserved space after equilibrium is independent of the permeability of coal cores.

Keywords

pressure-preserved coring, in-situ, coal-seam gas pressure

DOI

10.12363/issn.1001-1986.22.12.0934

Recommended Citation

CUI Pengfei, GAO Mingzhong, SHANG Delei, et al. (2023) "A preliminary study of pressure-preserved coring calculation principle and method for in-situ pressure in deep coal seams," Coal Geology & Exploration: Vol. 51: Iss. 8, Article 8.
DOI: 10.12363/issn.1001-1986.22.12.0934
Available at: https://cge.researchcommons.org/journal/vol51/iss8/8

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