Characterization of induced seismicity and associated microseismicity is an important challenge for enhanced oil recovery and development of tight hydrocarbon reservoirs. In particular, accurately correlating hypocenters of induced events to stratigraphic layers plays an important role in understanding the mechanisms of fault activation. Existing methods for estimating focal depth, however, are prone to a high degree of uncertainty. A comprehensive analysis of inferred focal depths is applied to induced events that occurred during completions of horizontal wells targeting the Montney Formation in British Columbia, Canada. Our workflow includes a probabilistic, nonlinear global-search algorithm (NonLinLoc), a hierarchical clustering algorithm for relative relocation (GrowClust), and depth refinement using the recently developed focal-time method. The focal-time method leverages stratigraphic correlations between P-P and P-S reflections to eliminate the need for an explicit velocity model developed specifically for hypocenter depth estimation. We find that this approach is robust in the presence of noisy picks and location errors from epicenters obtained using a global-search algorithm, but it is limited to areas where multicomponent 3D seismic data are available. We have developed a novel method to determine statics corrections to ensure that the passive seismic observations and 3D seismic data share a common datum in areas of moderate to high topography. Our results highlight the importance of transverse faults, which appear to provide permeable pathways for activation of other faults at distances of up to 2 km from hydraulic fracturing operations.

中文翻译：

---

焦点时间分析在改善诱导地震活动深度控制中的应用：以加拿大不列颠哥伦比亚省的蒙尼组为例

诱导地震活动性和相关的微地震活动的表征是提高致密烃储层采油率和开发能力的重要挑战。特别是，将诱发事件的震源与地层精确关联起来在理解断层激活机制中起着重要作用。但是，现有的估计焦深的方法容易产生高度的不确定性。对推断焦深的综合分析适用于在针对加拿大不列颠哥伦比亚省的蒙尼组的水平井完井过程中发生的诱发事件。我们的工作流程包括概率非线性非线性全局搜索算法（NonLinLoc），用于相对重定位的分层聚类算法（GrowClust），以及使用最近开发的聚焦时间方法进行深度细化。聚焦时间方法利用PP和PS反射之间的地层相关性来消除对专门为震源深度估计开发的显式速度模型的需求。我们发现，在存在使用全局搜索算法获得的震中出现噪声拾取和位置错误的情况下，该方法是鲁棒的，但仅限于可使用多分量3D地震数据的区域。我们已经开发出一种确定静校正的新颖方法，以确保被动地震观测和3D地震数据在中高地形区域共享相同的基准。我们的研究结果突出了横向断层的重要性，该断层似乎为距水力压裂作业最远2 km的其他断层的活化提供了渗透性途径。