Insight into Gas Threshold Pressure Gradient and Permeability of Coal Seam: Principle and Method for Field Test
Publication: Journal of Energy Engineering
Volume 149, Issue 6
Abstract
The flow regime of gas migration and production in a low-permeability coal seam includes desorption, diffusion, low-velocity nonlinear seepage, and linear seepage. However, the current field test methods of coal seam permeability in China are all based on linear seepage theory, leaving out the low-velocity nonlinear seepage with gas threshold pressure gradient. Therefore, a field test method for gas threshold pressure gradient and permeability is established in this paper. First, the two upward cross seam boreholes (the piezometric borehole and gas extraction borehole) are constructed in the untapped area of the floor drainage roadway with the low-permeability coal seam. After sealing the holes, the pressure measurement and gas extraction are carried out, respectively. Then, a radial flow mathematical model considering the gas threshold pressure gradient was constructed, and the model was solved by the COMSOL Multiphysics software. Finally, the gas threshold pressure gradient and permeability of the coal seam were obtained by fitting the simulated data of gas pressure and flow to the measured data in the field. The method was applied to the test of gas threshold pressure gradient and permeability before and after the hydraulic punching. Field test results show that this method can more accurately characterize the permeability in the gas extraction process of low-permeability coal seam than the traditional method.
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Data Availability Statement
All data, models, and code generated or used during the study appear in the published article.
Acknowledgments
The work was supported by the National Natural Science Foundation of China (42230804 and 42072193) and the Natural Science Foundation of Henan Province (222300420173). We are also grateful for the constructive comments by reviewers and editors on an earlier draft of this manuscript.
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© 2023 American Society of Civil Engineers.
History
Received: Jan 18, 2023
Accepted: Jul 20, 2023
Published online: Sep 12, 2023
Published in print: Dec 1, 2023
Discussion open until: Feb 12, 2024
ASCE Technical Topics:
- Coal
- Energy engineering
- Energy sources (by type)
- Engineering fundamentals
- Field tests
- Flow (fluid dynamics)
- Fluid dynamics
- Fluid mechanics
- Fluid velocity
- Fuels
- Gas flow
- Geomechanics
- Geotechnical engineering
- Hydrologic engineering
- Materials characterization
- Materials engineering
- Natural gas
- Non-renewable energy
- Permeability (material)
- Petroleum
- Seepage
- Soil mechanics
- Soil properties
- Tests (by type)
- Water and water resources
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