A Guide to Mitigating Seismicity From Wastewater Injection

Growing levels of induced seismicity are a major topic of concern in oil producing areas, although it has received little attention in Washington, D.C. However, around the country scientists and regulators are working hard to understand and mitigate the risk.

The StatesFirst working group on induced seismicity just released its report, “Potential Injection-Induced Seismicity Associated with Oil & Gas Development: A Primer on Technical and Regulatory Considerations Informing Risk Management and Mitigation.”

This report is a valuable contribution to our understanding of the causes and ways to prevent induced earthquakes, provided by the scientists and regulators in the states that are most affected. It also looks at the interaction between regulators and the public, and the report includes case studies of how states have responded to instances of suspected induced seismicity in California, Oklahoma, Ohio, Illinois, and Colorado.

The USGS has installed temporary seismic stations to pinpoint the location of small earthquakes that are usually not recorded by permanent seismic networks. Temporary networks are now operating in north Texas, central Oklahoma, southern Kansas, and near Decatur Ill., and Youngstown Ohio. USGS data and analysis as well as state scientific studies provided valuable information to the authors of the StatesFirst report.

The aim of the StatesFirst report is to share science, research and practical experience to give states tools to evaluate the possible connections between seismic events and injection wells and to mitigate earthquake risks. The analysis focuses on underground disposal of oilfield-produced fluids, including flowback fluids. Hydraulic fracturing and enhanced oil recovery were not considered, although they may possibly induce a very small number of felt seismic events.

The report starts with a clear and concise description of the mechanisms that trigger earthquakes then goes into the difficulties of differentiating between tectonic and induced earthquakes. In considering ways to manage and mitigate risk, the report argues that a one-size-fits-all approach is inappropriate given that geologic settings vary across the county. Major considerations that the report recommends when designing and permitting an injection well include site characterization, construction standards of buildings and other infrastructure, the proposed injection volumes, and estimates of the maximum potential seismic magnitude and ground motion.

The report differentiates two components of risk management:

• An induced-seismicity hazard, related to “… a fault of concern, sufficient pore pressure build-up in the area of the fault related to injection, and a pathway for communicating the pressure.”
• A risk of a person or property being harmed, which may be related to “… the potential magnitude of the earthquake, its associated ground motion, and the proximity of people and structures that might be affected.”

Finally, the report devotes a full chapter to the important topic of how to provide the public with information and respond to inquiries. The report stresses that a communication and response plan needs to be in place before it is necessary to respond to an incident. The authors stress that the goal of public communication is to understand the public’s perceptions, issues and concerns, and provide information in understandable language and format.

The report ends with the message that induced seismicity is complex and our understanding of it is rapidly changing so regulators need to be prepared for varied and perhaps unexpected occurrences of induced seismicity.

If you have general questions about induced seismicity see the U.S. Geological Survey (USGS) Myths and Misconceptions web page.

StatesFirst is an initiative of the Interstate Oil and Gas Compact Commission and the Ground Water Protection Council.