Key experimental technologies and their development directions for the exploration and production of deep coalbed methane
ObjectiveDeep coalbed methane (CBM) production enjoys advantages including rapid gas shows, high single-well yield, and continuous resource distribution, which establish deep CBM as a significant target for reserve growth and production addition of natural gas. However, the exploration and productio...
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| Main Authors: | , , , , , , , , , , , , , |
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| Format: | Article |
| Language: | zho |
| Published: |
Editorial Office of Coal Geology & Exploration
2025-01-01
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| Series: | Meitian dizhi yu kantan |
| Subjects: | |
| Online Access: | http://www.mtdzykt.com/article/doi/10.12363/issn.1001-1986.25.01.0046 |
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| Summary: | ObjectiveDeep coalbed methane (CBM) production enjoys advantages including rapid gas shows, high single-well yield, and continuous resource distribution, which establish deep CBM as a significant target for reserve growth and production addition of natural gas. However, the exploration and production of deep CBM are still confronted with many technical challenges, and there is a lack of studies on key experimental technologies related to the geological characteristics and engineering assessment of deep CBM reservoirs, the occurrence characteristics and production mechanisms of gas and water, the formulation of production systems, and methods for enhanced CBM recovery. Advances in ResearchGiven the characteristics of deep coal seams and CBM, this study identifies four challenges in the exploration and exploitation of deep coal seams: the collection of large coal samples, the high-temperature, high-pressure, and high-stress in-situ conditions, high-precision characterization and desorption of sub-nano- to nano-scale micropores, and the accurate determination of gas content. Furthermore, this study systematically analyzes the advances and challenges in experimental technologies for deep coals, involving the characterization of multi-scale pores and fractures, the assessment of absorption and gas-content properties, the mechanic characteristics and fracture propagation patterns of coals, and the dynamic patterns of fluid occurrence and production post-fracturing. ProspectsThis study posits seven development directions for deep CBM production and in-situ coal conversion experiments: (1) Clear, direct observation techniques for micropores (< 2 nm) in deep coal seams with ultra-low porosity and permeability, full-scale pore size splicing technology for multiscale pore structure characterized by abundant micropores, a few mesopores, and many macropores, and assessment techniques for pore-fracture connectivity. (2) Isothermal adsorption test technologies for raw coals considering the effects of deep coal seam wettability, fracturing fluid invasion, and high total dissolved solids (TDS) under high-temperature, high-pressure in-situ conditions; (3) Sealed coring devices and in-situ pressure-retaining coring technologies featuring high pressure retaining success rates, heat preservation rates, and traceable gas volume. (4) Nanoscience-based assessment technologies for gas and water occurrence in micropores in deep coal seams under high-temperature and high-pressure multi-field coupling, and experimental technologies for desorption, diffusion, and seepage across nano-micro-millimeter scales. (5) Techniques for developing and testing multifunctional mechanical experiment equipment applicable to in-situ conditions of deep coal seams featuring high stress, low modulus of elasticity, and high Poisson's ratio. (6) Experimental techniques for the purpose of enhancing CBM recovery of deep coal seams, including reservoir stimulation (microwaves, laser, and electric heating), stimulation for permeability enhancement (electromagnetic pulses, pulsed ultrasonic waves, and controlled shockwaves), displacement via CO2 injection, and mechanical pulsation with supercritical CO2. (7) Experimental techniques for in-situ coal conversion and utilization, including pyrolysis, underground coal gasification (UCG), geothermal utilization, and CO2 geological storage. Analyses reveal that there is an urgent need to establish the standards and regulations for the operational procedures of these experimental technologies, as required by objective demand for the exploration and production of deep CBM. These experimental technologies aim is to achieve environment protection, permeability enhancement, desorption promotion, and CO2 storage, thus providing vital support for the efficient production and utilization of deep CBM and coals and helping attain the goals of peak carbon dioxide emissions and carbon neutrality. |
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| ISSN: | 1001-1986 |