Laboratory Study on Fluid-Induced Fault Slip Behavior: The Role of Fluid Pressurization Rate
Laboratory Study on Fluid-Induced Fault Slip Behavior: The Role of Fluid Pressurization Rate
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DOI：
10.1029/2019gl086627
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发表时间：
2020-03-28
影响因子：
5.2
通讯作者：
Dresen, Georg
中科院分区：
文献类型：
--
作者：
Wang, Lei;Kwiatek, Grzegorz;Dresen, Georg
了解流体诱发断层滑动的物理机制对于改善与大规模流体注入相关的地震风险的缓解非常重要。我们在实验室中进行了流体诱导断层滑动实验的临界应力锯切砂岩样品具有高渗透率，使用不同的流体增压率。我们的实验结果表明，断层滑动行为是由流体增压率，而不是注入压力。缓慢的粘滑（峰值滑动速度< 4 μ m/s）是由快速的流体注入速率引起的，而滑动速度< 0.4 μ m/s的断层蠕动主要是对慢速流体注入速率的响应。当加载刚度大于断层刚度时，流体诱导断层滑移仍能保持力学稳定。独立的断层滑动模式，我们观察到动态摩擦弱化的人工断层在孔隙压力升高。我们的观察强调，不同的流体注入率可能有助于减少潜在的地震危险的现场规模的流体注入projects.Plain语言摘要人为诱发的地震从现场规模的流体注入projects.Plain语言摘要已被记录在世界各地，包括增强地热系统和深层污水注入。虽然很明显，流体压力在触发断层滑动中起着至关重要的作用，但诱发地震活动背后的物理机制仍然知之甚少。我们进行了实验室测试，在这里，我们提出了两个流体诱导的滑动实验进行渗透Bentheim砂岩样品横切断层，是临界应力。然后通过以不同的流体注入速率从样品的底端泵送水来触发断层滑动。结果表明，断层滑动受流体压力增加速率的控制，而不是流体压力的绝对大小。相反，相对快速，但稳定的滑动事件所造成的快速流体注入速率的插曲，断层蠕动观察到在缓慢的流体注入。实验断层的动摩擦系数在孔隙压力升高时会明显减弱，与断层滑动模式无关。这些结果可以提供一个更好的理解的复杂行为的流体诱导断层滑动的字段规模。
Understanding the physical mechanisms governing fluid-induced fault slip is important for improved mitigation of seismic risks associated with large-scale fluid injection. We conducted fluid-induced fault slip experiments in the laboratory on critically stressed saw-cut sandstone samples with high permeability using different fluid pressurization rates. Our experimental results demonstrate that fault slip behavior is governed by fluid pressurization rate rather than injection pressure. Slow stick-slip episodes (peak slip velocity < 4 mu m/s) are induced by fast fluid injection rate, whereas fault creep with slip velocity < 0.4 mu m/s mainly occurs in response to slow fluid injection rate. Fluid-induced fault slip may remain mechanically stable for loading stiffness larger than fault stiffness. Independent of fault slip mode, we observed dynamic frictional weakening of the artificial fault at elevated pore pressure. Our observations highlight that varying fluid injection rates may assist in reducing potential seismic hazards of field-scale fluid injection projects.Plain Language Summary Human-induced earthquakes from field-scale fluid injection projects including enhanced geothermal system and deep wastewater injection have been documented worldwide. Although it is clear that fluid pressure plays a crucial role in triggering fault slip, the physical mechanism behind induced seismicity still remains poorly understood. We performed laboratory tests, and here we present two fluid-induced slip experiments conducted on permeable Bentheim sandstone samples crosscut by a fault that is critically stressed. Fault slip is then triggered by pumping the water from the bottom end of the sample at different fluid injection rates. Our results show that fault slip is controlled by fluid pressure increase rate rather than by the absolute magnitude of fluid pressure. In contrast to episodes of relatively rapid but stable sliding events caused by a fast fluid injection rate, fault creep is observed during slow fluid injection. Strong weakening of the dynamic friction coefficient of the experimental fault is observed at elevated pore pressure, independent of fault slip mode. These results may provide a better understanding of the complex behavior of fluid-induced fault slip on the field scale.