Injection Induced Seismicity in Hot Resevoirs

强化的地热系统可能是该国清洁、可持续能源供应的主要贡献者。增强型地热库是一种工程地下热交换器，旨在改善传统的热液库，或在热储岩渗透率较低的情况下创建循环系统。这通常是通过注入加压流体来实现的。这种注入已被证明可以诱发地震活动。了解注入诱发地震活动的原因是利用这一资源的基础。了解诱发地震的机制对于开采该国丰富的页岩气储量和碳封存也是必要的。由于注水诱发地震活动的现场机制非常复杂，目前仍缺乏深入的了解。该项目将在非常专业的设备上进行一系列实验，这些设备可以模拟间歇泉地热场。这将带来对诱发地震活动背后的机制进行工程设计所需的理解，以便在不引发地震的情况下使用地下注入流体作为能源。该项目基于一系列精心设计的测试，每一次都会通知下一次。第一阶段是研究断层卸荷和剪切载荷增加对前震和破裂的影响。格拉泽的初步工作表明，动力学是完全不同的。这些实验将在实验室的地震机中进行。下一组实验将在格拉泽实验室的真三轴地热库模拟器中进行。与该设备集成的是一个高压锅炉，它用2兆帕的蒸汽注入250毫米的方块岩石，复制间歇泉喷发场。样品将被破碎，以表示一个岩体，而不是一个坚固的岩石立方体。我们将调查热收缩和注入水对蒸汽闪蒸的影响，作为断层减弱的直接原因。将对贯通裂缝和不断扩大的水力裂缝进行建模。将通过纳米地震成像来研究导致宏观破裂的动态微凸级位移“种子”。这是由绝对校准的纳米地震传感器实现的，其噪音下限为0.2 pm。多年来，基于地震学家使用的工具开发了实验室分析方法，以准确测量破裂运动学的绝对度量，包括震源-时间函数对MN的敏感性。因为类似的工具被用来研究间歇泉的地震活动，所以有可能合理地扩大我们的结果。

Enhanced geothermal systems are potentially a major contributor to the nation's supply of clean, sustainable energy. An enhanced geothermal reservoir is an engineered subsurface heat exchanger designed to improve a conventional hydrothermal reservoir, or to create a circulation system where hot reservoir rocks have low permeability. This is most often done by injection of pressurized fluids. This injection has been shown to induce seismicity. Understanding why injection-induced seismicity occurs is fundamental for utilizing this resource. Understanding the mechanisms of induced seismicity is also necessary for the exploitation of the country's rich deposits of shale gas, and for carbon sequestration. Because the in situ mechanisms of injection induced seismicity are so complex, there still is a lack of deep understanding. The project will carry out a set of experiments in very specialized equipment that can model the Geysers geothermal field. This will bring the understanding needed to engineer for the mechanisms behind induced seismicity so that subsurface injection of fluids for energy resources can be used without causing earthquakesThe project is based on a carefully designed sequence of tests, each informing the next. The first stage is the investigation of the effects of fault unloading vs. increased shear loading on foreshocks and rupture. Preliminary work by Glaser shows that the dynamics are quite different. These experiments will take place in a laboratory earthquake machine. The next set of experiments will take place in the Glaser lab's true-triaxial geothermal reservoir simulator. Integral to this device is a high pressure boiler that floods 250 mm cubes of rock with 2 MPa steam, duplicating the Geysers field. Specimens will be fractured to represent a rock mass rather than a solid cube of rock. We will investigate the effects of thermal contraction, and injected water flashing to steam, as proximate causes of fault weakening. Both through-going and growing hydraulic fractures will be modeled. The dynamic asperity-level displacement "seeds" that lead to macro-rupture will be studied through nano-seismic imaging. This is made possible by absolutely-calibrated nanoseismic sensors, which have a noise floor of 0.2 pm. Over many years, laboratory analysis methodologies have been developed based on tools used by seismologists, to accurately measure absolute metrics of rupture kinematics, including the source-time function to mN sensitivity. Because similar tools are used to study seismicity at the Geysers, it is possible to reasonably scale our results.