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在理论分析水压致裂起裂机理和起裂方向的基础上,应用煤岩损伤破裂过程渗流-应力耦合分析系统,对5种不同地应力条件下的本煤层水压致裂过程进行模拟,得到了煤体的起裂方向、起裂压力和扩展压力。研究发现:侧压系数λ<1时,煤体基本沿垂直方向起裂,起裂压力和扩展压力呈逐步增长的趋势;λ>1时,煤体的起裂方向为水平,起裂压力和扩展压力表现出平缓降低的趋势;在λ=1时,运用3种屈服准则进行了对比分析,得到了不同判别准则下的最小起裂水压。通过对λ=1.2时的受力状态进行深入分析,提出了压裂增透范围为宏观裂隙区、微裂隙贯通区、微裂隙产生区(受拉区)和原生裂隙扰动区(压应力恢复区)之和;利用数值图像处理得到的增透面积增长趋势符合二次函数的关系。
Based on the theoretical analysis of hydraulic crack initiation mechanism and fracture initiation direction, the hydraulic fracturing process of five coal seam under different ground stress conditions is simulated by using the seepage and stress coupled analysis system of coal damage and fracture. The direction of initiation of cracking, cracking pressure and expansion pressure were obtained. The results show that when the lateral pressure coefficient λ is less than 1, the coal body starts to rupture in the vertical direction and the cracking pressure and expansion pressure increase gradually. When λ> 1, the initiation direction of the coal body is horizontal, the cracking pressure and The expansion pressure showed a trend of gentle decrease. When λ = 1, three kinds of yield criteria were used for comparative analysis, and the minimum initiation hydraulic pressure under different criteria was obtained. Through the in-depth analysis of the stress state at λ = 1.2, it is proposed that the range of permeability increase should be macroscopic fracture zone, micro-fracture zone, micro-fracture zone (tension zone) and primary fracture disturbance zone ); The increase trend of antireflection area obtained by numerical image processing is in accordance with the quadratic function.