Abstract Dynamic wellbore stimulation technologies, such as high-energy gas fracturing, electrical pulse fracturing, hydraulic pulsation fracturing, are generally designed to multi-fracture the near-wellbore region through generating high energy pulse with intermediate or high loading rate. During the stimulating process, the dynamic strength and failure mode of saturated rocks around the wellbore can be largely affected by the transient intrusion of high energy fluid. Accordingly, an experimental method was developed to provide a method to apply the tailored pulse loading in the central borehole of the cylindrical rock samples. Three groups (Saturated + Center hole exposed (S-CHE), Saturated + Center hole wall isolated (S-CHI), Dry + Center hole wall isolated (D-CHI)) tests were carried out. The borehole fluid pressure-time curves and the failure modes of rock samples were tracked, analyzed and compared for all of the experiments. Experimental results demonstrate that: The relationship between rock dynamic strength and loading rate is monotonic direct proportionality. The dynamic strength of saturated rock shows a much stronger strain rate dependence than that of the dry rock. At the same loading rate, fluid penetration can largely weaken the dynamic strength of rock samples. The stress pulse generates a complex crushed zone around the wellbore, while the fluid penetration tends to produce radial multi-fractures. These phenomenons were explained using the micromechanics-based macroscopic damage theory, which is capable of obtaining the relationship between the fluid intrusion and the fracture deformation in the rock dynamic failure process.

中文翻译：

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动态增产过程中高能流体对井筒周围岩石破坏的瞬态侵入效应

摘要 动态井筒增产技术，如高能气体压裂、电脉冲压裂、水力脉动压裂等，一般是通过产生中高负荷率的高能脉冲对近井区进行多次压裂。在增产过程中，井筒周围饱和岩石的动态强度和破坏模式在很大程度上受到高能流体瞬时侵入的影响。因此，开发了一种实验方法以提供一种在圆柱形岩石样品的中心钻孔中施加定制脉冲载荷的方法。进行了三组（饱和 + 中心孔外露 (S-CHE)、饱和 + 中心孔壁隔离 (S-CHI)、干燥 + 中心孔壁隔离 (D-CHI)）测试。对所有实验都跟踪、分析和比较了钻孔流体压力-时间曲线和岩石样品的破坏模式。试验结果表明： 岩石动态强度与加载速率呈单调正比例关系。饱和岩石的动态强度表现出比干燥岩石强得多的应变率依赖性。在相同的加载速率下，流体渗透会大大削弱岩样的动态强度。应力脉冲在井眼周围产生复杂的破碎带，而流体渗透往往会产生径向多重裂缝。使用基于微观力学的宏观损伤理论解释了这些现象，