Response of Induced Seismicity to Injection Rate Reduction: Models of Delay, Decay, Quiescence, Recovery, and Oklahoma
Response of Induced Seismicity to Injection Rate Reduction: Models of Delay, Decay, Quiescence, Recovery, and Oklahoma
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诱发地震活动对注入率降低的响应：延迟、衰变、静止、恢复和俄克拉荷马模型
DOI：
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发表时间：
2018
影响因子：
5.4
通讯作者：
J. Riffault
中科院分区：
文献类型：
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作者：
D. Dempsey;J. Riffault
当注入引发的地震活动对社区构成风险时，通常会降低注入速度或停止运营。这适用于单井和井群，例如俄克拉荷马州西部触发地震活动感兴趣区域内的井，州监管机构于 2016 年强制要求减少 40% 的体积。在这里，我们量化了诱发地震活动如何响应注入减少。我们引入了理想几何形状中的压力扩散模型，与稳态加压和地震触发的速率状态模型相结合。我们发现，地震活动爆发的延迟以及随后的还原后行为（地震活动速率的衰减、有时静止和恢复）取决于临界触发压力以及扩散和速率状态参数。我们调整了我们的模型，以复制俄克拉荷马州西部废水注入引发的地震活动的爆发时间、峰值和最近的下降速度。我们的分析表明 Arbuckle 地层的扩散率很高（44 至 277 m2/s 之间）。推断临界触发压力在0.021至0.077MPa之间，基底4.5公里深度处的流体超压估计增加了0.190MPa。我们模拟了 2025 年的三种未来地震活动情况。确定 2018 年的注入速度（已经低于国家监管机构规定的限制），我们发现很有可能再次发生 M ≥ 5 级地震。这表明俄克拉荷马州西部的减排任务目前水平还不够。
When injection‐induced seismicity poses a risk to communities, it is common to reduce the injection rate or halt operations. This applies both to individual wells and well clusters, such as those within the Area of Interest for Triggered Seismicity in Western Oklahoma, where in 2016 a 40% volume reduction mandate was imposed by the state regulator. Here we quantify how induced seismicity responds to an injection reduction. We introduce models of pressure diffusion in idealized geometries coupled to steady state pressurization and rate‐state models of earthquake triggering. We find that the delay in seismicity onset and then postreduction behavior—decay, sometimes quiescence, and recovery of the seismicity rate—depend on the critical triggering pressure and on diffusion and rate‐state parameters. We have adapted our model to replicate the timing of onset, peak, and recent pace of decline of seismicity triggered by wastewater injection in Western Oklahoma. Our analysis implies that diffusivity in the Arbuckle formation is high (between 44 and 277 m2/s). The critical triggering pressure is inferred to be between 0.021 and 0.077 MPa, and fluid overpressure at 4.5‐km depth in the basement is estimated to have increased by as much as 0.190 MPa. We simulate future seismicity out to 2025 for three scenarios. Fixing the 2018 injection rate, already less than the limit imposed by the state regulator, we find a high likelihood of further M ≥ 5 earthquakes. This suggests that the volume reduction mandate in Western Oklahoma is, at present levels, inadequate.