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Fervo’s Approach to Induced Seismicity Management

February 28, 2024
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As the leader in next-generation geothermal, Fervo prioritizes environmental health and safety above all else, including the management of induced seismicity – earthquakes or tremors resulting from human activity – which can result from geothermal development. In this post, we cover Fervo’s approach to seismicity mitigation and management, which follows a best practice protocol put in place by the Department of Energy. This protocol applies during all Fervo operations including drilling, stimulation, and production and will be rigorously adhered to during all of Fervo’s projects. For example, you can find a discussion of our implementation of the protocol for Project Red, Fervo’s successful pilot project commissioned in 2023, in our white paper published last year.

Components of Seismicity Management

Fervo segments its approach to seismicity mitigation and management into three major categories: planning, measurement, and response. By building a bank of historical seismic events and collecting our own, third-party-validated events in real-time, Fervo can make data-driven decisions that prioritize safety during all phases of operations. By devising and approving a detailed response, communication, and reporting plan in advance of operations, Fervo can properly adjust its field work and stakeholder engagement in the event of seismic activity.

Component 1: Planning

Effective induced seismicity mitigation begins with proactive planning. Before starting subsurface operations, Fervo’s operations and resource teams draft an induced seismicity screening report that evaluates seismic risk near the project site. Fervo’s Cape Station screening report provides a fault map of the area, a geologic prognosis based on our understanding of fault zones, and a characterization of natural fractures in subsurface rock.

This background research, coupled with sophisticated modeling, allows Fervo to account for potential seismic risk when designing subsurface operations.

Component 2: Seismicity Measurement

With a strong plan in place, Fervo then focuses on accurate seismicity measurement. At Cape Station, Fervo has built a robust seismic monitoring network using three tools: partner organization seismometers (specialized instruments used to record the motion of the ground during an earthquake, even ones far too small to be felt by humans), Fervo seismometers, and a seismic event catalog. Together, these strategies enable Fervo to collect high-fidelity seismic information before subsurface activity poses meaningful risks to the project, workers, and the surrounding community.

Some monitoring stations are installed several hundred feet under ground and others are installed on the surface. This network serves to “listen” to the underground, where seismic events may occur. These seismic events, characterized by short-term vibrations of the earth, are triggered by changes in fluid pressure and subsurface stress. These events may vary in intensity, ranging from events that are imperceptible to those that cause vibrations able to be felt on surface.

Partner Monitoring

Fervo benefits from partner organizations’ widespread deployment of seismometers near Cape Station. As a result of the Utah Frontier Observatory for Research in Geothermal Energy (FORGE), seventeen permanent seismic stations surround our project site.

The University of Utah, which oversees FORGE, publishes detailed information about the date, time, location, magnitude, and depth of seismic events through the University of Utah Seismographic Stations (UUSS) website. Third party experts review and analyze this data, providing both Fervo and FORGE with trustworthy information about seismic activity in Beaver County. Accelerometers at the Blundell geothermal plant and Milford high school help provide additional information on ground motion before, during, and after stimulation.

Fervo Monitoring

Fervo supplements these third-party seismic readings with its own array of six seismometers. These tools enable Fervo to collect its own on-site data and validate readings from UUSS, increasing the accuracy of seismic information. Additionally, with multiple Fervo seismometers across Cape Station, Fervo can guarantee network functionality even if one monitor fails, faces an unplanned outage, or requires routine maintenance. Around-the-clock tracking helps promote rapid risk management and safe operations.

A map of Fervo and partner seismic stations near the Cape Station project area.

Seismic Event Catalog

Finally, Fervo has produced a backward-looking seismic event catalog to determine whether seismic activity on-site aligns with seismic trends in southwest Utah. According to the United States Geological Survey’s Comprehensive Earthquake Catalog, seven seismic events between magnitude 2.1 and 2.8 were detected between 1999 and 2023 within 10 km of Cape Station. This historic data provides Fervo with an appropriate benchmark to characterize real-time seismic data and evaluate on-site subsurface risks.

Statewide seismicity patterns throughout Utah (Pankow et al., 2019).

Component 3: Seismicity Response

Monitoring seismicity is only the first step to promoting local health and safety. Ultimately, data must feed into a prompt Induced Seismicity Mitigation Protocol (ISMP) that allows on-site work to account for changing seismic conditions. Fervo’s ISMP, which adheres to best practices outlined by US Department of Energy’s Induced Seismicity Mitigation Protocol for Enhanced Geothermal Systems, encompasses operational changes, stakeholder communication, and formal, conclusive external reporting.

Operations

Responsible seismicity response starts with operational adaptability. Fervo maintains a clear traffic light protocol to structure operational decisions based on observed seismicity.

Our traffic light system includes the following categories:

Green: Seismic events remain below the critical threshold for response of M < 2.0

  • Operations continue as planned.

Amber: A seismic event is observed with magnitude ranging from 2.0 ≤ M < 3.0

  • Safely pause operations for a minimum of 6 hours while continuing to monitor seismicity levels.
  • If appropriate, resume operations and implement any required operational adjustments.

Red: A seismic event is observed with magnitude M ≥ 3.0

  • Safely pause operations for a minimum of 24 hours while continuing to monitor seismicity levels.
  • Engage in communications outreach to local stakeholders as well as academic partners, state and federal research institutions, and regulatory officials.
  • If appropriate, resume operations and implement any required operational adjustments.

Communications

Fervo then shares seismicity-related updates with the local community using a defined communication procedure based on stakeholder mapping conducted at the onset of Cape Station. To the best of our ability, Fervo maintains consistent, proactive engagement with all individuals and entities included on our stakeholder register.

Communication standards align with our operational traffic light system and differ depending on the severity of seismic activity. Fervo attends Beaver County Commission and Milford City Council meetings on a quarterly basis and will discuss and review all green and amber seismic events with county and city officials during these meetings. Fervo will post the presentations it delivers at these meetings on the Cape Station project website.

For all seismic events in the red category, Fervo will post a notice to the Cape Station project website and contact all identified stakeholders through their preferred means of communication to provide details about the event and outline remediation plans.

Reporting

At the end of Cape Station, Fervo will conduct an after action review with the project team and local, state, and federal authorities to identify opportunities to improve operational safety. The after action review will culminate in a final report that provides a summary of field operations, compiled daily seismicity reports, a CSV catalog of events across the project – beginning with the commencement of downhole work – and a written summary of the after action review meeting with local stakeholders.

This final report will help inform Fervo’s seismicity management at other prospects, reinforcing our culture of continuous improvement. To live our value of building things that last, we will hold ourselves to high safety transparency standards not only at Cape Station, but across our portfolio of next-generation geothermal assets.

Select References

Majer, E., Nelson, J., Robertson-Tait, A., and Wong, I. (2012). Protocol for Addressing Induced Seismicity Associated with Enhanced Geothermal Systems. Technical report No. DOE/EE-0662. https://www.energy.gov/eere/geothermal/articles/protocol-addressing-induced-seismicity-associated-enhanced-geothermal.

Norbeck, J.H. and Latimer, T. (2023). Commercial-scale demonstration of a first-of-a-kind enhanced geothermal system. https://doi.org/10.31223/X52X0B.

Pankow, K.L., Potter, S., Zhang, H., Trow, A.J., and Record, A.S. (2019). Micro-seismic characterization of the Utah FORGE site, in Allis, R., and Moore, J.N., editors, Geothermal characteristics of the Roosevelt Hot Springs system and adjacent FORGE EGS site, Milford, Utah: Utah Geological Survey Miscellaneous Publication 169-G, 10 p., https://doi.org/10.34191/MP-169-G.

Utah FORGE. (2020). Utah FORGE Induced Seismicity Mitigation Plan. https://gdr.openei.org/files/1319/Induced%20Seismicity%20Mitigation%20Plan%20Revision%2006012021%20Final.pdf.