Geological structure of the Paradox Valley Region, Colorado, and relationship to seismicity induced by deep well injection
Geological structure of the Paradox Valley Region, Colorado, and relationship to seismicity induced by deep well injection
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科罗拉多州悖论谷地区的地质结构及其与深井注入引发的地震活动的关系
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发表时间：
2014
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通讯作者：
Sarah A. Derouin
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作者：
Vanessa M. King;L. Block;W. Yeck;C. K. Wood;Sarah A. Derouin
垦务局（垦务局）在科罗拉多西部的帕里河谷经营一口深注入井。自1985年以来，已经记录了地震活动，自1991年开始注入操作以来，检测到超过5900次可能的诱发地震，使该项目成为注入诱发地震活动长期发展的独特而有价值的案例研究。可能诱发的地震发生在一个复杂的模式与集群分开的2公里或更长的地震间隙，并已观察到高达16公里的注入井。为了评估地下地质结构如何控制诱发地震活动的发生，我们将地震位置与一组地质模型进行了比较，该模型是填海工程在钻探注入井之前委托的。我们的分析表明，观测到的地震活动模式的许多方面可以归因于复杂的地质结构。地震的深度和位置通常与主要注入目标地层的结构趋势一致，在模型的不确定性范围内，并且一些映射的基底断层似乎在地震位置中充当边界，这表明它们是流动的障碍。此外，大多数事件遵循预测的流体流动模式，其趋势是西北-东南，并环绕帕里河谷。地震活动模式的某些特征，如注入井西北部地震活动的早期发生和明显的聚类，无法用当前的地质模型解释，可能与未绘制的地质特征或应力场的局部变化有关。
The Bureau of Reclamation (Reclamation) operates a deep injection well at Paradox Valley in western Colorado. Seismicity has been recorded since 1985, with more than 5900 likely induced earthquakes detected since injection operations began in 1991, making this project a unique and valuable case study in the long‐term development of injection‐induced seismicity. Likely induced earthquakes occur in a complex pattern with clusters separated by aseismic gaps of 2 km or more, and have been observed up to 16 km from the injection well. To evaluate how the subsurface geologic structure may control the occurrence of induced seismicity, we compare the earthquake locations to a set of geologic models that Reclamation commissioned prior to drilling the injection well. Our analysis indicates that many aspects of the observed seismicity pattern can be attributed to the complex geologic structure. The earthquake depths and locations are generally consistent with the structural trends of the primary injection target formation, within the uncertainty of the models, and some of the mapped basement faults appear to serve as boundaries in the earthquake locations, suggesting that they are barriers to flow. Additionally, the majority of events follow the predicted fluid flow pattern, which trends northwest–southeast and wraps around Paradox Valley. Some features of the seismicity pattern, such as the early onset of seismicity to the northwest of the injection well and the distinct clustering, are not explained by the current geologic models and may be related to unmapped geologic features or local variations in the stress field.