Large-Scale Fracture Systems Are Permeable Pathways for Fault Activation During Hydraulic Fracturing
Large-Scale Fracture Systems Are Permeable Pathways for Fault Activation During Hydraulic Fracturing
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DOI：
10.1029/2020jb020311
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发表时间：
2021-03-01
影响因子：
3.9
通讯作者：
Eaton, David W.
中科院分区：
文献类型：
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作者：
Igonin, Nadine;Verdon, James P.;Eaton, David W.
由于流体注入（包括水力压裂）而诱发的地震活动在世界范围内越来越普遍;然而，水力压裂导致断层活化的机制仍不清楚。在这里，我们表明，预先存在的裂缝网络有助于将流体压力传递到发生动态破裂的较大断层。北美水力压裂诱发地震活动的研究经常使用区域地震仪网络的观测结果，距离为10公里，因此缺乏解决方案来回答有关触发机制的一些关键问题。为了进行更详细的分析故障激活的机制，我们使用的数据来自一个密集的传感器阵列位于加拿大阿尔伯塔的水力压裂现场。事件震源的时空分布，再加上地震各向异性的测量，揭示了预先存在的断裂走廊，允许通信的流体压力扰动较大的故障，在1公里或以上的距离。预先存在的渗透性裂缝网络的存在可以显著增加受孔隙压力增加影响的岩石体积，从而增加诱发地震的可能性。这项研究表明，了解预先存在的天然裂缝的连通性，以评估与页岩地层水力压裂相关的潜在地震危险的重要性，并提供了一个详细的案例，阐述了由于水力压裂引起的地震活动。
Induced seismicity due to fluid injection, including hydraulic fracturing, is an increasingly common phenomenon worldwide; yet, the mechanisms by which hydraulic fracturing causes fault activation remain unclear. Here we show that preexisting fracture networks are instrumental in transferring fluid pressures to larger faults on which dynamic rupture occurs. Studies of hydraulic fracturing-induced seismicity in North America have often used observations from regional seismograph networks at distances of 10s of km, and as such lack the resolution to answer some of the key questions about triggering mechanisms. To carry out a more detailed analysis of the mechanisms of fault activation, we use data from a dense sensor array located at a hydraulic-fracturing site in Alberta, Canada. The spatiotemporal distribution of event hypocenters, coupled with measurements of seismic anisotropy, reveal the presence of preexisting fracture corridors that allowed communication of fluid-pressure perturbations to larger faults, over distances of 1 km or more. The presence of preexisting permeable fracture networks can significantly increase the volume of rock affected by the pore-pressure increase, thereby increasing the probability of induced seismicity. This study demonstrates the importance of understanding the connectivity of preexisting natural fractures for assessing potential seismic hazards associated with hydraulic fracturing of shale formations and offers a detailed case exposition of induced seismicity due to hydraulic fracturing.