Target Area Selection for Residual Coalbed Methane Drainage in Abandoned Multi-Seam Mines
Abstract
1. Introduction
2. Evaluation of CBM Resources in Songzao Mining Area
2.1. Overview of Geological and Hydrological Conditions in Mining Area
2.2. Evaluation of CBM Resources in Mining Area
3. Theoretical Calculation of ‘Two Zones’ Height in Songzao Coal Mine
3.1. Project Profile
3.2. Theoretical Calculation of ‘Two-Band’ Height
4. Numerical Investigation of Mining-Induced Stress-Fracture Field Evolution in Songzao Coal Mine
4.1. Model Development
4.2. Stress Evolution Characteristics of Overburden Strata During Multi-Seam Mining
4.3. Fracture Development Characteristics of Overburden Strata During Multi-Seam Mining
4.4. The Characteristics of Increasing Permeability of Overlying Strata in Multi-Coal Seam Mining
5. Optimization of CBM Extraction Target Area in Fracture Zone
5.1. Height Prediction of Fracture Zone in Abandoned Goaf
5.2. Determination of CBM Extraction Target Area
6. Conclusions
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
Nomenclature
| Variable/Symbol | Description | Units |
| coalbed gas resources | m3 | |
| coal reserves | t | |
| the coal seam average gas content | m3/t | |
| Hk | the height of the caving zone | m |
| M | the thickness of the mined coal seam | m |
| Hli | the height of the fracture zone | m |
| the comprehensive mining thickness of the upper and lower coal seams | m | |
| the thickness of the upper coal seam mining | m | |
| the thickness of the lower coal seam mining | m | |
| the normal distance between the upper and lower coal seams | m | |
| the caving ratio of the lower coal seam | / | |
| Kk | the permeability in the k direction | m2 |
| Kk0 | the permeability in the k direction in the initial state | m2 |
| Kni | the stiffness of cracks in i directions | Pa/m |
| Knj | the stiffness of cracks in j directions | Pa/m |
| v | the Poisson ‘s ratio of coal | / |
| ∆σi | the stress variation in i directions | Pa |
| ∆σj | the stress variation in j directions | Pa |
| ∆σk | the stress variation in k directions | Pa |
| bi | the crack openings in the i directions | m |
| bj | the crack openings in the j directions | m |
| the height of the caving zone at the end of the first stage | m | |
| the bulking coefficient of the caved rock in the caving zone at the end of the first stage | / | |
| the bulking coefficient of the caved rock in the caving zone at the end of the second stage | / | |
| the reduction in the unloading height of the fracture zone in the second stage | m | |
| the height of the fracture zone at the end of the first stage | m | |
| the height of the fracture zone at the end of the second stage | m |
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| Name of Indicator | Songzao | Fengchun | Datong Yi | Shihao | Yuyang |
|---|---|---|---|---|---|
| Geological structure complexity | Medium | Complex | Medium | Medium | Medium |
| Average buried depth (m) | 298 | 302 | 466 | 485 | 351 |
| Inclination degree of coal seam | Inclined | Steep inclined | Gentle inclined | Gentle inclined | Gentle inclined |
| Height of water outlet point (m) | +333 | +523 | +460 | +480 | +470 |
| Water accumulation in the goaf (104 m3) | 981 | 127 | 3384 | 2510 | 2000 |
| Goaf area (km2) | 12.55 | 3.36 | 18.36 | 3.84 | 6.31 |
| Water-free space in the goaf (104 m3) | 1426 | 333.5 | 0 | 132 | 0 |
| CBM emission (m3/min) | 114.37 | 54.02 | 267.27 | 202.18 | 137.4 |
| Maximum CBM content (m3/t) | 28.51 | 26.87 | 24.03 | 29.45 | 29.44 |
| Remaining coal resources (104 t) | 4786.6 | 4484.8 | 8418.2 | 7860.6 | 3391.9 |
| Name of Indicator | Songzao | Fengchun | Datong Yi | Shihao | Yuyang |
|---|---|---|---|---|---|
| Coal consumption (104 t) | 5242.1 | 1940.27 | 4392.91 | 2752.7 | 3303.6 |
| Rate of recovery | 80% | 80% | 80% | 78.69% | 68.40% |
| Coal Seam | Mining Thickness/m | Caving Zone/m |
|---|---|---|
| K2b | 0.56 | 0.58–4.98 |
| K1 | 0.97 | 2.41–6.81 |
| K3b | 2.50 | 8.11–12.51 |
| Lithologic Characteristics | Density (kg·m−3) | Bulk Modulus (GPa) | Shear Modulus (GPa) | Angle of Internal Friction (°) | Cohesion (MPa) | Tensile Strength (MPa) |
|---|---|---|---|---|---|---|
| Sandy mudstone | 2558 | 2.69 | 2.15 | 33 | 4.43 | 1.68 |
| Limestone | 2600 | 9.32 | 6.54 | 31 | 6.67 | 4.57 |
| Coal | 1400 | 2.31 | 1.63 | 18 | 1.88 | 0.52 |
| Mudstone | 2330 | 3.12 | 2.56 | 23 | 3.89 | 1.17 |
| Sandstone | 2752 | 8.86 | 5.26 | 33 | 5.72 | 3.53 |
| Argillaceous limestone | 2559 | 5.85 | 2.40 | 42 | 3.51 | 1.65 |
| Siliceous limestone | 2320 | 4.38 | 3.32 | 30 | 3.32 | 2.45 |
| Calcareous mudstone | 2550 | 2.45 | 1.86 | 33 | 2.15 | 1.53 |
| Bauxite mudstone | 2620 | 2.33 | 1.54 | 35 | 2.07 | 1.12 |
| Mining Stage | Fracture Zone Development Height/m | ||
|---|---|---|---|
| Empirical Formula Prediction | Numerical Simulation Results | ||
| Toward | Dip | ||
| K2b coal seam | 18.06 m | 20.46 m | 22.60 |
| K1 coal seam | 29.70 m | 31.40 m | 32.60 |
| K3b coal seam | 69.76 m | 72.30 m | 74.50 m |
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Share and Cite
Li, G.; Xiu, Y.; Liu, Q.; Zhang, B.; Duan, M.; Yang, Y.; Guo, C. Target Area Selection for Residual Coalbed Methane Drainage in Abandoned Multi-Seam Mines. Appl. Sci. 2025, 15, 10619. https://doi.org/10.3390/app151910619
Li G, Xiu Y, Liu Q, Zhang B, Duan M, Yang Y, Guo C. Target Area Selection for Residual Coalbed Methane Drainage in Abandoned Multi-Seam Mines. Applied Sciences. 2025; 15(19):10619. https://doi.org/10.3390/app151910619
Chicago/Turabian StyleLi, Gen, Yaxin Xiu, Qinjie Liu, Bin Zhang, Minke Duan, Youxing Yang, and Chenye Guo. 2025. "Target Area Selection for Residual Coalbed Methane Drainage in Abandoned Multi-Seam Mines" Applied Sciences 15, no. 19: 10619. https://doi.org/10.3390/app151910619
APA StyleLi, G., Xiu, Y., Liu, Q., Zhang, B., Duan, M., Yang, Y., & Guo, C. (2025). Target Area Selection for Residual Coalbed Methane Drainage in Abandoned Multi-Seam Mines. Applied Sciences, 15(19), 10619. https://doi.org/10.3390/app151910619

