Geoscience Visual Presentation G05: Evolution of coal strength with dewatering and coal seam gas depletion: an integrated approach
Jimmy Xuekai Li A *A
Dr Jimmy X. Li is a geoscientist and has 10 years of experience in the upstream oil and gas industry and 8 years of experience in academic research. His professional background spans a range of technical domains, including formation evaluation, petrophysics, and borehole geophysics, with a focus on both field operations and technical consulting. Between 2007 and 2017, he held various technical and management roles at Halliburton Energy Services Inc. Currently, Dr Li is a Postdoctoral Research Fellow at the School of Mechanical and Mining Engineering at the University of Queensland (UQ), where his research interests centre on geophysics, geomechanics, and geotechnical engineering. |
Abstract
Geoscience Visual Presentation G05
Understanding the response of coal mechanical properties to dewatering and gas depletion is critical for estimating borehole stability and designing infill coal seam gas (CSG) wells. Despite its importance, the full impact of these processes on coal strength remains little explored. This study aims to quantify these effects through a combination of results from micro-computed tomography (micro-CT) imaging, sonic testing, and mechanical testing on coal samples. Micro-CT imaging provides insights into coal’s internal structure by focusing on parameters such as fracture porosity and fracture intensity (P32 factor). Sonic testing measures dynamic properties, including P-wave and S-wave velocities (Vp and Vs) and dynamic Young’s modulus (Ed), under both dry and wet conditions. Mechanical testing with acoustic emission monitoring evaluates static properties like Young’s modulus (Es) and uniaxial compressive strength (UCS). The key findings follow: (i) micro-CT imaging shows a strong correlation between coal fracture porosity and P32, offering detailed insights into the coal microstructure; (ii) mechanical testing reveals that dry samples exhibit a 10% higher Es and 31% greater UCS than wet samples, suggesting that dewatering increases coal strength but potentially also promotes embrittlement; and (iii) wet samples show higher Vp and Ed in sonic tests, indicating water saturation significantly influences sonic measurements. These findings improve the understanding of dewatering and gas depletion effects, laying the groundwork for more advanced geomechanical models in CSG operations.
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Keywords: coal seam gas, coal strength, dewatering, micro-CT imaging, P-wave velocity, UCS, Young’s modulus.
Dr Jimmy X. Li is a geoscientist and has 10 years of experience in the upstream oil and gas industry and 8 years of experience in academic research. His professional background spans a range of technical domains, including formation evaluation, petrophysics, and borehole geophysics, with a focus on both field operations and technical consulting. Between 2007 and 2017, he held various technical and management roles at Halliburton Energy Services Inc. Currently, Dr Li is a Postdoctoral Research Fellow at the School of Mechanical and Mining Engineering at the University of Queensland (UQ), where his research interests centre on geophysics, geomechanics, and geotechnical engineering. |
