Zang Arno, Zimmermann Günter, Hofmann Hannes, Niemz Peter, Kim Kwang Yeom, Diaz Melvin, Zhuang Li, Yoon Jeoung Seok
Helmholtz Centre Potsdam GFZ German Research Centre for Geosciences, Telegrafenberg, 14473, Potsdam, Germany.
Institute of Geosciences, University of Potsdam, 14469, Potsdam, Germany.
Sci Rep. 2021 Mar 24;11(1):6780. doi: 10.1038/s41598-021-86094-5.
The ability to control induced seismicity in energy technologies such as geothermal heat and shale gas is an important factor in improving the safety and reducing the seismic hazard of reservoirs. As fracture propagation can be unavoidable during energy extraction, we propose a new approach that optimises the radiated seismicity and hydraulic energy during fluid injection by using cyclic- and pulse-pumping schemes. We use data from laboratory-, mine-, and field-scale injection experiments performed in granitic rock and observe that both the seismic energy and the permeability-enhancement process strongly depend on the injection style and rock type. Replacing constant-flow-rate schemes with cyclic pulse injections with variable flow rates (1) lowers the breakdown pressure, (2) modifies the magnitude-frequency distribution of seismic events, and (3) has a fundamental impact on the resulting fracture pattern. The concept of fatigue hydraulic fracturing serves as a possible explanation for such rock behaviour by making use of depressurisation phases to relax crack-tip stresses. During hydraulic fatigue, a significant portion of the hydraulic energy is converted into rock damage and fracturing. This finding may have significant implications for managing the economic and physical risks posed to communities affected by fluid-injection-induced seismicity.
控制地热和页岩气等能源技术中诱发地震活动的能力，是提高储层安全性和降低地震风险的一个重要因素。由于在能量开采过程中裂缝扩展不可避免，我们提出了一种新方法，即通过采用循环和脉冲抽水方案，在流体注入过程中优化辐射地震活动和水能。我们使用在花岗岩中进行的实验室、矿山和现场规模注入实验的数据，观察到地震能量和渗透率增强过程都强烈依赖于注入方式和岩石类型。用可变流速的循环脉冲注入取代恒定流速方案：（1）降低破裂压力；（2）改变地震事件的震级-频率分布；（3）对最终的裂缝模式产生根本性影响。疲劳水力压裂的概念通过利用降压阶段来松弛裂纹尖端应力，为这种岩石行为提供了一种可能的解释。在水力疲劳过程中，很大一部分水能转化为岩石损伤和破裂。这一发现可能对管理受流体注入诱发地震影响的社区所面临的经济和物理风险具有重要意义。
