纵向切槽水力压裂作为一项强烈动压巷道切顶卸压技术，核心是控制裂缝开裂以及扩展方向，然而裂缝在定向起裂后通常受最大主应力的影响而发生偏转，裂缝的扩展方向与地应力条件、切槽角度、泵流量以及岩石力学性质等多种因素有关。对纵向切槽水力压裂多因素影响下的裂缝偏转规律展开研究，为纵向切槽水力压裂钻孔施工设计提供1种借鉴方法。采用ABAQUS软件中的XFEM模块，建立纵向切槽水力压裂二维模型，通过与前期纵向切槽水力压裂物理试验结果对比，实现了数值模型可行性验证，进而建立大尺寸纵向切槽水力压裂模型对煤矿顶板砂岩条件下的纵向切槽水力压裂裂缝偏转规律展开了详细研究。结果表明：水平应力比为重要的裂缝偏转距影响因素，在垂直主应力为10 MPa，最小水平主应力为6 MPa，水平应力比由1.5增加到3.5过程中，裂缝偏转距先后减小55.3%、56.9%和41%；切槽角度对裂缝扩展路径影响较大，对裂缝偏转距影响相对较小；水平应力比为1.5与2.0两种条件下，泵流量由30 L/min增加到180 L/min过程中，裂缝偏转距不断增大，且具有较大增长幅度，在水平应力比为2.5条件下，裂缝偏转距的增长幅度明显减弱；水平应力比分别为1.5、2.0、2.5的3种条件下，泵流量90 L/min对应的裂缝偏转距分别为4.05、1.81、0.75 m，可通过大幅提升泵流量，实现偏转距的较大增长；该研究对纵向切槽水力压裂泵流量的选取以及不同条件下钻孔间距的确定具有参考意义。

Longitudinal grooving hydraulic fracturing is a kind of pressure relief technology for roadway cutting under strong dynamic pressure. The core is to control the cracking and propagation direction of cracks. However, the cracks are usually deflected under the influence of the maximum principal stress after directional fracturing. The propagation direction of the crack is related to various factors such as in-situ stress conditions, grooving angle, pump flow rate and rock mechanical properties. Research on the crack deflection law under the influence of multiple factors of longitudinal groove hydraulic fracturing is carried out to provide a reference method for the construction design of longitudinal groove hydraulic fracturing drilling. The XFEM module in ABAQUS software was used to establish the two-dimensional model of longitudinal grooving hydraulic fracturing. The feasibility verification of the numerical model was achieved by comparing with the previous physical test results of longitudinal grooving hydraulic fracturing, and then the large-scale longitudinal grooving hydraulic fracturing model was established, and the fracture deflection law of longitudinal grooving hydraulic fracturing under the condition of coal mine roof sandstone was studied in detail. The results show that the horizontal stress ratio is an important factor affecting the crack deflection distance. When the vertical principal stress is 10 MPa, the minimum horizontal principal stress is 6 MPa, and the horizontal stress ratio increases from 1.5 to 3.5, the crack deflection distance decreases by 55.3%, 56.9% and 41% respectively. The cutting angle has a great influence on the crack propagation path and a relatively small influence on the crack deflection distance; When the horizontal stress ratio is 1.5 and 2.0, the crack deflection distance increases continuously and has a large increase range when the pump flow increases from 30 L / min to 180 L/min. When the horizontal stress ratio is 2.5, the growth rate of the crack deflection distance is significantly reduced; When the horizontal stress ratio is 1.5, 2.0 and 2.5，respectively, the crack deflection distances corresponding to the pump flow of 90 L / min are 4.05m, 1.81m and 0.75m respectively. A large increase in the deflection distance can be achieved by greatly increasing the pump flow. The study provides significant reference for the selection of flow rate of longitudinal grooved hydraulic fracturing pump and the determination of borehole spacing under different conditions.

0 引言

1 数值模型可靠性验证

   1.1 数值模型设计

   1.2 数值模拟结果对比

2 大尺寸纵向切槽水力压裂数值模拟

3 水平应力比对裂缝偏转距影响规律

4 切槽角度对裂缝偏转距影响规律

5 泵流量对裂缝偏转距影响规律

   5.1 水平应力比为1.5条件下

   5.2 水平应力比为2.0条件下

   5.3 水平应力比为2.5条件下

6 结论