Hydraulic Fracturing‐Induced Seismicity

• Published in: Reviews of geophysics (1985) Vol. 58; no. 3
• Main Authors: Schultz, Ryan, Skoumal, Robert J., Brudzinski, Michael R., Eaton, Dave, Baptie, Brian, Ellsworth, William
• Format: Journal Article
• Language: English
• Published: 01.09.2020
• Subjects: hydraulic fracturing; induced seismicity
• ISSN: 8755-1209; 1944-9208
• DOI: 10.1029/2019RG000695

Hydraulic fracturing (HF) is a technique that is used for extracting petroleum resources from impermeable host rocks. In this process, fluid injected under high pressure causes fractures to propagate. This technique has been transformative for the hydrocarbon industry, unlocking otherwise stranded resources; however, environmental concerns make HF controversial. One concern is HF‐induced seismicity, since fluids driven under high pressure also have the potential to reactivate faults. Controversy has inevitably followed these HF‐induced earthquakes, with economic and human losses from ground shaking at one extreme and moratoriums on resource development at the other. Here, we review the state of knowledge of this category of induced seismicity. We first cover essential background information on HF along with an overview of published induced earthquake cases to date. Expanding on this, we synthesize the common themes and interpret the origin of these commonalities, which include recurrent earthquake swarms, proximity to well bore, rapid response to stimulation, and a paucity of reported cases. Next, we discuss the unanswered questions that naturally arise from these commonalities, leading to potential research themes: consistent recognition of cases, proposed triggering mechanisms, geologically susceptible conditions, identification of operational controls, effective mitigation efforts, and science‐informed regulatory management. HF‐induced seismicity provides a unique opportunity to better understand and manage earthquake rupture processes; overall, understanding HF‐induced earthquakes is important in order to avoid extreme reactions in either direction. Plain Language Summary Earthquakes can be induced by a number of anthropogenic sources. One category of induced earthquake is caused by hydraulic fracturing (HF)—a technique used by industry to produce petroleum from normally impermeable rocks. The widespread use of HF has resulted in a significant increase in induced earthquakes. In this paper, we provide a review of all the reported cases of HF‐induced earthquakes: in Canada, the United States, the United Kingdom, and China. Some of these cases are exceptional, having events as large as 5.7 ML or earthquakes triggered up to 1.5 km away. That said, there are common themes that are repeated in all of the cases: similar waveforms, swarm‐like sequences, proximity to HF stimulation in time and space, and that only the small minority of HF wells induced earthquakes. Likely, these common themes are related to the physics of HF stimulation and the geology of the target formations. Many of the proposed interpretations are still open‐ended research areas, such as consistent recognition of cases, proposed triggering mechanisms, geologically susceptible conditions, identification of operational controls, effective mitigation efforts, and science‐informed regulatory management. Overall, a better understanding of these earthquakes will allow for adequately balanced management of their risks. Key Points Induced seismicity caused by hydraulic fracturing has been recognized in basins around the world Common themes are observed in disparate cases of hydraulic fracturing‐induced seismicity A better understanding of the commonalities will yield better recognition of cases and management of hazards/risks