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煤系岩层水力裂缝扩展轨迹及压裂效果智能预测研究

Hydraulic fracture propagation path and intelligent prediction of fracturing effects in coal measure strata

  • 摘要: 为解决由岩层界面和层间强度差异引起的煤系岩层水力压裂裂缝扩展轨迹及压裂范围有效控制的难题, 采用有限–离散元方法模拟研究了煤系岩层水力裂缝扩展规律, 发现多因素耦合作用下煤系岩层水力裂缝扩展轨迹有12种主要模式, 可归纳为穿过岩层界面扩展、穿过岩层界面扩展的同时沿着岩层界面扩展、沿着岩层界面扩展和在岩层界面处停止扩展4类; 建立了融合BP神经网络、差分进化算法和灰狼优化算法的混合人工智能模型, 用以预测煤系岩层水力裂缝扩展轨迹和压裂效果; 分析了不同地应力条件下岩性强度差异系数、岩层界面倾角、岩层界面强度系数、注入速率和定向射孔角度变化时水力裂缝在岩层界面处扩展轨迹的变化规律, 揭示了煤系岩层水力裂缝扩展轨迹的主要控制因素及重要程度; 提出了基于BP-DEGWO混合人工智能预测模型的煤系岩层水力压裂技术方案智能优化设计方法, 为利用人工智能算法进行水力压裂的关键技术方案优化设计和压裂效果预测提供参考。

     

    Abstract: To address the challenges in controlling hydraulic fracture propagation trajectories and stimulated volumes within multi-lithologic coal measure strata, particularly those caused by formation interfaces and interlayer strength variations, a combined finite-discrete element method (FDEM) was used to investigate hydraulic fracture behavior. The results show twelve distinct propagation modes under multifactor coupling conditions, which can be classified into four categories: interface penetration, penetration with interface extension, interface tracking, and interface arrest. A novel hybrid artificial intelligence model integrating BP neural networks with differential evolution (DE) and grey wolf optimization (GWO) algorithms (BP-DEGWO) was developed to predict fracture trajectories and stimulation effectiveness. Key controlling factors, including rock strength contrast coefficient, interface dip angle, interfacial strength, injection rate and perforation angle were identified, and their relative importance under varying in-situ stress conditions was quantified. A further intelligent optimization framework for hydraulic fracturing design in stratified formations was proposed based on the BP-DEGWO model. This approach provides a predictive tool for fracture geometry in heterogeneous coal-bearing strata and a methodological reference for AI-assisted fracturing optimization. The findings are instructive in enhancing stimulation efficiency in multi-lithologic unconventional reservoirs.

     

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