Numerical Investigation of Factors Influencing Multiple Hydraulic Fracture Propagation from Directional Long Boreholes in Coal Seam Roofs
Abstract
1. Introduction
2. Methodology
2.1. Governing Equation of Rock Deformation and Damage
2.2. Seepage Equation
2.3. Influence of Damage on Physical Field Parameters
3. Numerical Modelling and Validation
3.1. Numerical Model Establishment
3.2. Model Validation
4. Analysis of Factors Influencing Hydraulic Fracture Propagation Behavior
4.1. Influence of Pumping Rate on Multi-Fracture Propagation
4.2. Influence of Compressive Strength on Multi-Fracture Propagation
4.3. Influence of In Situ Stress Difference on Multi-Fracture Propagation
4.4. Influence of Segment Length on Multi-Fracture Propagation
5. Engineering Application
5.1. Fracturing Design and Construction Process
5.2. Fracturing Effect Validation
6. Conclusions
- (1)
- During the process of increasing the segment spacing from 12 m to 40 m, the fracture length decreased by 12%, limiting the overall fracture propagation. However, excessively small segment length can cause fractures to be influenced by the induced stress of adjacent clusters, leading to asymmetric propagation. Therefore, segment length should be optimized based on the specific objectives of the fracturing operation. Considering economic factors and fracture length, this study recommends a segment spacing of 30 m for the field application.
- (2)
- During the progressive increase of pumping rate from 5 to 40 m3/h, a 98% extension in fracture length was observed. However, underground space constraints impose limitations on equipment capacity, including flow rate and pump pressure. Thus, fracturing designs should be tailored to the characteristics of the working face, segment length, and flow parameters. Based on the results of numerical simulations, a pumping rate of 40 m3/h is recommended for the field application.
- (3)
- Segmented hydraulic fracturing in underground directional boreholes exhibits significant responses in resistivity, microseismic activity, and mine pressure variations. The experimental results indicate that this technique effectively weakens hard coal seam roofs and improves mine pressure distribution, facilitating coal mine production planning and management.
- (4)
- The numerical simulation framework developed in this study is flexible and adaptable. By adjusting key geological parameters, it can be extended to assess hydraulic fracturing performance under varying geological conditions.
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
References
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Parameter Name | Symbol | Value | Unit | Parameter Name | Symbol | Value | Unit |
---|---|---|---|---|---|---|---|
Heterogeneity Coefficient | m | 10 | / | Initial Permeability | k0 | 5 × 10−15 | m2 |
Compressive Strength | fc0 | 40 | MPa | Pumping rate | q | 40 | m3/h |
Poisson’s Ratio | υ | 0.2 | / | Injection Pressure | p | 25 | Mpa |
Internal Friction Angle | φ | 40 | ° | Fluid Density | ρw | 1 × 103 | kg/m3 |
Initial Porosity | Φ0 | 0.1 | / | Maximum Principal Stress | σ1 | 11 | Mpa |
Residual Porosity | φr | 0.001 | / | Biot Coefficient | α | 0.5 | / |
Model Length | L | 140 | m | Fluid Viscosity | μw | 1 × 10−3 | Pa·s |
Model Width | H | 140 | m | Porosity of Matrix Region | nr | 0.1 | / |
Initial Hydraulic Fracture Length | a | 1 | m | Minimum horizontal stress | σ2 | 6 | Mpa |
Segment length | d | 30 | m |
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Yang, M.; Lv, S.; Meng, Y.; Wang, X.; Wang, S.; He, J. Numerical Investigation of Factors Influencing Multiple Hydraulic Fracture Propagation from Directional Long Boreholes in Coal Seam Roofs. Appl. Sci. 2025, 15, 6521. https://doi.org/10.3390/app15126521
Yang M, Lv S, Meng Y, Wang X, Wang S, He J. Numerical Investigation of Factors Influencing Multiple Hydraulic Fracture Propagation from Directional Long Boreholes in Coal Seam Roofs. Applied Sciences. 2025; 15(12):6521. https://doi.org/10.3390/app15126521
Chicago/Turabian StyleYang, Maolin, Shuai Lv, Yu Meng, Xing Wang, Sicheng Wang, and Jiangfu He. 2025. "Numerical Investigation of Factors Influencing Multiple Hydraulic Fracture Propagation from Directional Long Boreholes in Coal Seam Roofs" Applied Sciences 15, no. 12: 6521. https://doi.org/10.3390/app15126521
APA StyleYang, M., Lv, S., Meng, Y., Wang, X., Wang, S., & He, J. (2025). Numerical Investigation of Factors Influencing Multiple Hydraulic Fracture Propagation from Directional Long Boreholes in Coal Seam Roofs. Applied Sciences, 15(12), 6521. https://doi.org/10.3390/app15126521