Disposal of industrial wastewater and activities such as ${\mathrm{C}\mathrm{O}}_2$ underground sequestration depend upon pressure conditions within deep geologic reservoirs. Sometimes, injection and storage are associated with induced seismicity, suggested to result from reservoir compartmentalization, leakage into faults, or other mechanisms in the subsurface. To understand subsurface pressure conditions within a major regional disposal reservoir, the Arbuckle Group of Oklahoma, we monitored the water levels in 15 inactive injection wells. The wells were monitored at 30-s intervals, with eight wells monitored since September 2016, and an additional seven from July 2017. All the wells were monitored until early March 2020. Since 2016, hydraulic head decreased in 13 of the 15 wells, proportional to near-borehole fluid pressure even considering decreasing regional injection volumes during this period. The well pressures respond to three types of perturbations: (i) gravitational fluctuations (a.k.a. solid-earth tides) (ii) distal and proximal earthquakes, and (iii) injections into nearby wells. Parameterization of tidal responses illustrates that the near wellbore environments have negative fluid flux (i.e., are leaking). Earthquakes cause differing pressure responses from well to well, with some highly sensitive to proximal events, some to distal events, and some apparently insensitive. Injections have variable impacts in some cases masking tidal and earthquake pressure signals. Collectively, there appears to be a threshold injection rate above which well pressure becomes less sensitive to the volume of injections within 15 km. Multi-scale geological structure and temporal permeability changes are likely controlling the pressure field, indicating leakage of fluids across the system.

中文翻译：

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俄克拉荷马州中北部处置储层的压力监测：对地震活动和地质储存的影响


工业废水的处置和 ${\mathrm{C}\mathrm{O}}_2$ 地下封存等活动取决于深地质储层内的压力条件。有时，注入和储存与诱发地震有关，被认为是由储层区室化、泄漏到断层或地下的其他机制引起的。为了了解俄克拉荷马州主要区域处置油藏 Arbuckle Group 的地下压力状况，我们监测了 15 口非活动注入井的水位。这些井以 30 秒的间隔进行监测，自 2016 年 9 月以来监测了 8 口井，从 2017 年 7 月开始监测了另外 7 口井。直到 2020 年 3 月初，所有井都受到了监测。自 2016 年以来，15 口井中有 13 口井的水力水头下降，与近井眼流体压力成正比，即使考虑到在此期间区域注入量的减少。井压对三种类型的扰动做出反应：（i） 重力波动（又名固体地球潮汐），（ii） 远端和近端地震，以及 （iii） 注入附近的井。潮汐响应的参数化表明，近井筒环境具有负流体通量（即泄漏）。地震会引起不同的压力响应，有些对近端事件高度敏感，有些对远端事件高度敏感，有些则明显不敏感。注入会产生不同的影响，在某些情况下会掩盖潮汐和地震压力信号。总的来说，似乎存在一个阈值注入速率，超过该阈值，井压对 15 公里内的注入量变得不那么敏感。 多尺度地质结构和时间渗透率变化可能控制着压力场，表明整个系统中的流体泄漏。