Induced earthquake source process imaging and groundwater chemistry monitoring in the Western Canada sedimentary basin

在过去的5年里，北美非常规油气开采过程中注入流体可能引发的地震数量急剧增加，包括以前的地震平静区。特别是，不列颠哥伦比亚省东北部和艾伯塔省发生与水力压裂作业有关的4级或更大地震，导致油井生产暂时停止，并在当地社区引起安全担忧。尽管地震监测网增密，但注入式地震的详细震源过程和触发阈值仍然是地震危险性评估和减灾的关键挑战。在这个项目中，我们建议结合创新的地球物理、水文地质和地球化学监测技术和数值工具，对卑诗省东北部和阿尔伯塔省西部的两口水力压裂井和一口处置井的诱发震源过程进行定量成像和建模。在每个目标地点，我们将安装由宽带地震仪和综合地震大地测量系统组成的密集阵列，用于记录诱发地震的地震仪，以及用于增强干涉卫星孔径雷达地面运动成像的角度反射器。我们还将在目标地点进行地下水化学和同位素调查，以确定与流体注入有关的时间变化，重点是潜在的地震前兆信号。现场观测将被用来约束孔隙弹性模型，以模拟由于注入而引起的流体压力和固体基质应力变化，并用于设计注入策略，以降低在先前存在的断层上触发地震滑动的可能性。该项目的成果将为我们的支持机构GSC的公共政策制定以及各省油气委员会的监管政策调整提供公正的科学知识。

In the past 5 years, there has been a drastic increase in the number of earthquakes potentially induced by fluid injection during unconventional oil and gas extraction in North America, including previously seismically quiescent areas. In particular, the occurrences of magnitude 4 and greater earthquakes associated with hydraulic fracturing operations in northeast British Columbia and Alberta has led to temporarily shut-down of well production and caused safety concerns among local communities. Despite the densification of seismic monitoring network, the detailed source process and triggering threshold of injection induced earthquakes remains a critical challenge to seismic hazard assessment and mitigation. In this project, we proposed to incorporate innovative geophysical, hydrogeological and geochemical monitoring techniques and numerical tools, to quantitatively image and model induced seismicity source processes at two hydraulic fracturing wells and one disposal well in northeast BC and west Alberta. At each target site, we will install a dense array composed of broadband seismometers and integrated seismo-geodetic systems for recording seismographs of induced earthquakes, and angled reflectors for enhanced Interferometry Satellite Aperture Radar ground motion imaging. We will also conduct groundwater chemistry and isotope surveys at the target sites, in order to identify temporal variations related to fluid injection with a focus on potential earthquake precursory signals. Field observations will be used to constrain the poroelastic model for simulating fluid pressure and solid matrix stress changes due to injection, and for designing injection strategies that reduce the likelihood of triggered seismic slip on pre-existing faults. The outcome of this project will provide unbiased scientific knowledge for the public policy making by our supporting organization GSC as well as regulatory policy adjustment by provincial oil and gas commissions.