The uptick in earthquakes corresponding with increased drilling and produced water disposal has been of great concern. Seeking scientific understanding of the reasons for increased seismicity and determining whether or not it has been induced by human activity has been a key focus. Welcome to an interview with Jeremy Boak, Ph.D., Director of the Oklahoma Geological Survey, which has demonstrated leadership in investigating induced seismicity.

What is your name and your experience in geology?

Dr. Jeremy Boak started as the Director of the Oklahoma Geological Survey in July 2015. Before coming to Oklahoma, he was Director of the Center for Oil Shale Technology and Research at the Colorado School of Mines. He co-chaired the Oil Shale Symposium from 2006-2015. Boak served as a project manager at Los Alamos National Laboratory and the U. S. Department of Energy (DOE) Yucca Mountain Project, and as an exploration geologist at ARCO in Anchorage, Denver and Bakersfield. Dr. Boak has B.A., M. S., and Ph. D. degrees from Harvard University, and an M.S. from the University of Washington, all in Geological Sciences.

What is induced seismicity and why is it important?

Induced seismicity refers to earthquakes that are caused by human activity. A variety of human activities can cause earthquakes. Mine blasts sometimes cause sufficient modification of stress fields to induce earthquakes. In addition, large adjustments in mass at or near the surface can also alter stress fields. These generally result from filling or emptying fluids from reservoirs. Both Lake Meade and the reservoir behind the Oroville dam caused earthquakes as they were filled (M5.8 in the case of Oroville, I believe). Extraction of hot water for geothermal power plants commonly induces seismic activity, and earthquakes have been attributed to oil and gas extraction in Texas and the Groningen Field in the Netherlands. The government is considering shutting in that field because of the seismic activity. An additional mechanism for induced seismicity is increase of pore pressure in deep-seated faults due to generally low-pressure injection of wastewater, primarily produced formation water, in sedimentary reservoirs that communicate with deep-seated faults in crystalline basement. This is the accepted cause of the large increase in seismicity in Oklahoma beginning in 2009, and of earthquakes in western Canada and Ohio, although increasing attention is also being put on the importance of poro-elastic stress changes, also caused by injection. Injection at high pressure has also triggered earthquakes near hydraulic fracturing operations in Canada, Oklahoma, and Ohio.

What is the current thinking about the relationship between wastewater injection and induced seismicity in Oklahoma?

The current view is that oil and gas industry disposal of wastewater is responsible both for the increase in seismicity in Oklahoma, and for its decline as disposal has reduced by about 1.5 million barrels per day. The parallel decline is as important as the rise in supporting this interpretation. The decline in injection reflects the effects both of market forces (the sharp drop in oil prices in 2014-2015) and of regulatory action (directives of the Oklahoma Corporation Commission).

Please describe the 2-day workshop that was held in Norman, Oklahoma on induced seismicity. What was the goal?

The purpose of the 2018 Oklahoma Seismicity Workshop was to allow researchers from Oklahoma and other states, Federal agencies, the energy industry, and other interested parties to meet and discuss models of tectonic versus-induced earthquakes, as well as explore practical procedures to mitigate seismic hazard. Approximately 100 people attended the workshop, despite the ice storm which prevented many local registrants from attending. 36 talks came from authors at 13 universities, five state geological surveys and the U. S. Geological Survey, two national Laboratories, four companies, one state agency and one consultant. The focus was on Oklahoma, but related events in Kansas, as well as developments in Arkansas and Texas were also prominently featured.

What were some of the presentations about? Where are areas of research?

Session topics included Spirit of Collaboration, Earthquake Catalogs, Differentiating Natural and Induced Seismicity, Geophysical Characterization, Geological and Reservoir Characterization, Structure and Stress, Regional and Play-Based Analyses of Brine Management vs. Seismic, Pressure Propogation and Poro-Elastic Stress, Hydraulic Fracturing and Mitigation Strategies, and Hazards, Engineering, and the Built Environment.

What are some of the future directions?

It is clear that the topic of earthquakes induced by hydraulic fracturing will be expanding in scope and depth, which probably means a focus on understanding how these are induced, and on potential best practices (or at least catalogs of tested and successful options) for mitigation of frack induced seismicity. Models of injection induced seismicity are just beginning to be shown, and these are likely to increase in sophistication in the future. It is still clear that science struggles to provide decision support to regulators facing the potential for increased seismicity in their areas. Regulators still have only one tool to reduce seismicity reducing injection, and current guidance from the scientific end does not necessarily provide refined answers to how to balance local and regional reductions. Interpretation of causal relationships between specific (more local) groups of wells and groups of earthquakes is not yet sophisticated enough to provide refined recommendations. The integration of geologic constraints on hydrologic connection between injection wells and potentially active faults is happening only in a limited way, and will require the evaluation of multiple scenarios for a given case.

What is the role of the OGS in understanding induced seismicity and developing solutions?

The Oklahoma Geological Survey is well positioned to participate with the scientific community in identifying the relevant technical questions and working out answers. We are the custodians of the richest database of information regarding a presently unique case of induced seismicity, and detailed local knowledge of the earthquake and injection catalogs will be essential to providing robust answers to the many remaining questions. We are still working to provide a quality-checked database of injection data, without which, many conclusions will remain significantly uncertain. For example, while the records for injection before 2009 have not been rigorously quality checked, injection as far back as 2000 may be important in understanding the early development of seismicity beginning in 2009. Some problems that were recognized in the more recent data (up to several million barrels per month in one region) have only recently been resolved. This is tedious work not well-recognized by the research community.

In addition, we would like to significantly enhance the quality of the publicly available seismic network by installing a suite of high quality research seismometers across much of the state. This requires substantial investment. Despite publishing three annual hazard assessment that pointed out risk of damaging earthquakes in Oklahoma equivalent to areas in Southern California, the U. S. Geological Survey continues to provide very substantial funding to California agencies, but none to Oklahoma. The U. S. Department of Energy recently rejected all proposals relating to induced seismicity in a Funding Opportunity which specifically addressed this topic. We believe that industry can be induced to match some portion of funding, but still feel the stewardship of state and Federal lands warrants government support to such an effort.