Abstract Hydraulic fracturing is the key technology employed to alter the permeability of tight reservoirs. In this article, the discrete element fluid–solid coupling method is improved, and sinusoidal stress waves are applied at the boundary of a heterogeneous reservoir to simulate perturbation. The influence of stress wave frequency on the mode of crack propagation in the hydraulic fracturing process and the internal stress changes in specimens under different in situ stress ratios are investigated. The simulation results suggest that (1) under a constant injection rate, an increased frequency is associated with a gradual increase in the breakdown pressures, an increase in the time required for cracking breakdown, and faster propagation of cracks propagating; and (2) the hydraulic fracture propagation direction obviously deflects towards the stress wave propagation direction, and the failure mode becomes more complicated under the combined action of the ground stress and the stress wave; and (3) the maximum principal stress inside the specimen is compressive stress, and the curves of the maximum principal stress and maximum shear stress are periodic vibration, with the characteristics of a large amplitude at a low frequency and a small amplitude at a high frequency. The initiation of cracks near the injection hole results from a reduction in the maximum principal stress and an increase in the maximum shear stress. The analysis indicates that the stress wave has a non-negligible influence on hydraulic fracturing and provides a better guideline for understanding the mechanical nature of hydraulic fracturing under the influence of stress perturbation.

中文翻译：

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应力扰动下非均质油藏水力裂缝行为机理的数值分析？

摘要 水力压裂是改变致密储层渗透率的关键技术。本文改进了离散元流固耦合方法，在非均质储层边界施加正弦应力波来模拟扰动。研究了应力波频率对水力压裂过程中裂纹扩展方式的影响以及不同地应力比下试件的内应力变化。模拟结果表明：（1）在恒定注入速率下，频率的增加与破裂压力的逐渐增加、破裂破裂所需时间的增加以及裂纹扩展的更快扩展有关；(2)水力裂缝传播方向明显偏向应力波传播方向，在地应力和应力波的共同作用下破坏模式更加复杂；(3)试件内部的最大主应力为压应力，最大主应力和最大剪应力曲线为周期性振动，具有低频大振幅、高频小振幅的特点. 注入孔附近裂纹的产生是由于最大主应力的减小和最大剪切应力的增加。