Abstract For the mitigation of micro-seismicity during hydraulic stimulation, we introduce the concept of time-delayed pressurization (TDP) which involves arresting the constant-rate process of borehole pressurization for a given delay period, and then resuming it until breakdown occurs. The additional fluid permeation into a porous media by the TDP scheme allows for the manipulation of pore fluid pressure buildup near a borehole, thereby resulting in the mechanical and seismic behaviors at failure in a controlled manner. Laboratory fracturing experiments with acoustic emission monitoring were conducted for several delay periods using mortar specimens to evaluate the breakdown pressure and acoustic emission (AE) in the TDP fracturing process. In addition, the morphological characteristics of induced fractures were visually investigated by 3D X-ray CT analysis on the fractured specimens. Numerical simulations using a phase-field approach were also performed to further examine the evolution of pore pressure during the fracturing process. The results show the considerable volume of permeated fluid and the elevated pore pressure during the delay period are the main factors responsible for the decreased breakdown pressure and AE.

中文翻译：

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水力增产过程中用于操纵击穿压力和声发射的延时加压的实验和数值研究

摘要 为了减轻水力增产过程中的微地震，我们引入了延时加压 (TDP) 的概念，它涉及在给定的延迟时间内阻止钻孔加压的恒定速率过程，然后恢复它直到发生故障。通过 TDP 方案额外的流体渗透到多孔介质中，允许操纵钻孔附近的孔隙流体压力，从而以受控方式导致失效时的机械和地震行为。使用砂浆试样进行了几个延迟时间段的声发射监测的实验室压裂实验，以评估 TDP 压裂过程中的击穿压力和声发射 (AE)。此外，通过对断裂试样的 3D X 射线 CT 分析，直观地研究了诱导断裂的形态特征。还进行了使用相场方法的数值模拟，以进一步检查压裂过程中孔隙压力的演变。结果表明，延迟期间大量渗透流体和升高的孔隙压力是导致击穿压力和AE降低的主要因素。