Enhanced Gas Drainage via Gas Injection Displacement Based on Hydraulic Flushing: Numerical Simulation and Field Test.
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| Title: | Enhanced Gas Drainage via Gas Injection Displacement Based on Hydraulic Flushing: Numerical Simulation and Field Test. |
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| Authors: | Yang, Xin1,2 (AUTHOR) xinyangbk89@163.com, Tan, Feiyan1,2 (AUTHOR), Zhang, Qingcheng3 (AUTHOR) |
| Source: | Energies (19961073). May2026, Vol. 19 Issue 9, p2061. 18p. |
| Subject Terms: | *Gas extraction, *Fluid injection, *Field research, *Computer simulation, *Permeability, *Coalbed methane |
| Geographic Terms: | China |
| Abstract: | Hydraulic flushing is an effective permeability enhancement technology for coal seams in underground coal mines and has been widely applied in several mining areas in China. However, in low-permeability coal seams, gas drainage from hydraulic flushing boreholes often enters a rapid depletion phase, and achieving secondary enhanced drainage remains a critical challenge. To address this issue, this study investigates a synergistic gas drainage technology that combines gas injection displacement with hydraulic flushing. Taking the No. 3 coal seam in the Lu'an mining area of China as the research object, the optimal process parameters of this synergistic technology are systematically determined through numerical simulation and validated by underground field tests. A fully coupled numerical model incorporating the adsorption–desorption–seepage processes of the CH4/N2/O2 ternary gas system is established. The influences of injection spacing and injection pressure on drainage performance are systematically analyzed. Simulation results identify the optimal process parameters as an injection spacing of 3.5 m and an injection pressure of 1.4 MPa. Under these conditions, the relative coal permeability reaches a maximum of 1.06, the permeability enhancement zone fully covers the region between the injection and drainage boreholes, and the coal seam gas content decreases to the critical threshold of 8 m3/t in approximately 235 days. The model is quantitatively validated using 82-day field monitoring data from the synergistic module, with a relative error of approximately 1.1% between the simulated and field-derived recovery ratios. Subsequently, four sets of underground engineering trials—conventional drainage, gas injection displacement alone, hydraulic flushing alone, and the synergistic technology—are conducted in the target coal seam based on the optimized parameters. Statistical analysis of the 82-day field data shows that the synergistic technology achieves a cumulative pure methane volume of 4.83 m3, outperforming conventional drainage by 85.8% (4.83 m3 compared with 2.60 m3), gas injection alone by 23.5% (4.83 m3 compared with 3.91 m3), and hydraulic flushing alone by 52.4% (4.83 m3 compared with 3.17 m3). The mean flow rate of the synergistic module during the injection phase reaches 0.070 ± 0.012 L/min, significantly higher than that of gas injection alone (0.044 ± 0.011 L/min). This study provides economically feasible theoretical and technical support for efficient gas drainage in low-permeability coal seams in underground mines. [ABSTRACT FROM AUTHOR] |
| Database: | Energy & Power Source |
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| Abstract: | Hydraulic flushing is an effective permeability enhancement technology for coal seams in underground coal mines and has been widely applied in several mining areas in China. However, in low-permeability coal seams, gas drainage from hydraulic flushing boreholes often enters a rapid depletion phase, and achieving secondary enhanced drainage remains a critical challenge. To address this issue, this study investigates a synergistic gas drainage technology that combines gas injection displacement with hydraulic flushing. Taking the No. 3 coal seam in the Lu'an mining area of China as the research object, the optimal process parameters of this synergistic technology are systematically determined through numerical simulation and validated by underground field tests. A fully coupled numerical model incorporating the adsorption–desorption–seepage processes of the CH4/N2/O2 ternary gas system is established. The influences of injection spacing and injection pressure on drainage performance are systematically analyzed. Simulation results identify the optimal process parameters as an injection spacing of 3.5 m and an injection pressure of 1.4 MPa. Under these conditions, the relative coal permeability reaches a maximum of 1.06, the permeability enhancement zone fully covers the region between the injection and drainage boreholes, and the coal seam gas content decreases to the critical threshold of 8 m3/t in approximately 235 days. The model is quantitatively validated using 82-day field monitoring data from the synergistic module, with a relative error of approximately 1.1% between the simulated and field-derived recovery ratios. Subsequently, four sets of underground engineering trials—conventional drainage, gas injection displacement alone, hydraulic flushing alone, and the synergistic technology—are conducted in the target coal seam based on the optimized parameters. Statistical analysis of the 82-day field data shows that the synergistic technology achieves a cumulative pure methane volume of 4.83 m3, outperforming conventional drainage by 85.8% (4.83 m3 compared with 2.60 m3), gas injection alone by 23.5% (4.83 m3 compared with 3.91 m3), and hydraulic flushing alone by 52.4% (4.83 m3 compared with 3.17 m3). The mean flow rate of the synergistic module during the injection phase reaches 0.070 ± 0.012 L/min, significantly higher than that of gas injection alone (0.044 ± 0.011 L/min). This study provides economically feasible theoretical and technical support for efficient gas drainage in low-permeability coal seams in underground mines. [ABSTRACT FROM AUTHOR] |
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| ISSN: | 19961073 |
| DOI: | 10.3390/en19092061 |
