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Introduction
Seismic activity that develops as a result of human action—“induced seismicity”—has been recognized for decades and the physical causes are well understood (NRC, 2013). In the past 7 to 8 years, a significant increase has occurred in the number of induced earthquakes that have been felt by people in several regions of the United States and the genesis of many of these earthquakes has been attributed to wastewater injection and disposal related to oil and gas development. These earthquakes, though generally of small magnitude, have been felt in a number of states including Arkansas, Colorado, Kansas, Ohio, Oklahoma, Pennsylvania, and Texas (e.g., Frohlich et al., 2011; Horton, 2012; Ellsworth, 2013). Although with much less frequency, some of these events have also been linked to fluid injection related to hydraulic fracturing in the United States, Canada, and Great Britain1 (e.g., Farahbod et al., 2015; Skoumal et al., 2015; Deng et al., 2016).
In the past decade, rapid advances in oil and gas production technologies, the proliferation of larger numbers of producing oil and gas fields, and oil and gas production from water-rich rock formations have resulted in the need to manage increasingly larger volumes of produced water.2 A common management approach for produced water is to inject the water into deep wells for permanent disposal (NRC, 2010; NASEM, 2017). Because of the potential unintended consequence of generating small earthquakes as a result of this kind of water disposal, well operators and others in the private sector, regulators, government and academic researchers, non-governmental organizations, and the public have been interested in understanding the specific (local) conditions—both the geological and geomechanical conditions in the subsurface and the operating conditions at the surface as fluid is injected – associated with these events and to find ways to mitigate and manage the associated risk. As a result, the numbers of scientific and engineering technical papers and conferences, as well as forums for dialogue among these groups and affected communities have burgeoned in
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1 See http://earthquakes.bgs.ac.uk/research/events/BlackpoolMay2011.html (accessed September 2017).
2 Produced water is water from underground formations that is brought to the surface during oil and gas production and is the greatest volume byproduct associated with oil and gas production (NASEM, 2017).
the past several years and have been accompanied by significant advances in understanding the circumstances that may lead to induced seismic events and some measures that may be employed to mitigate and manage their occurrence (e.g., Kim, 2013; McGarr et al., 2015; Segall and Lu, 2015; Weingarten et al., 2015; Chang and Segall, 2016; Elsworth et al., 2016; Snee and Zoback, 2016; Petersen et al., 2016).
The National Academies of Sciences, Engineering, and Medicine released a consensus report in 2013 that specifically addressed induced seismicity related to fluid injection for energy production (NRC, 2013). The information collected for that report was current through approximately the close of 2011, just as the numbers of induced earthquakes related to wastewater disposal in the United States were increasing. The intent of the second day of the workshop of the National Academies Roundtable on Unconventional Hydrocarbon Development, held on December 2, 2016, was to highlight some of the advances that had been made since the publication of the 2013 National Academies report in understanding induced seismicity (see Box 1.1 for statement of task and specifically, point 4). The workshop presentations and discussion addressed current understanding of fluid-injection-related induced seismicity, existing data and information needs and gaps, monitoring and assessment technologies and needs, and collaborative approaches to managing risk.
WORKSHOP OVERVIEW
This workshop was organized by a planning committee assembled for the purpose of developing the workshop program and convening the event (see Appendix A for the agenda). Day 2 of the workshop focused specifically on induced seismicity. The proceedings for Day 1 are published in a separate companion volume to this one.
Dr. Brian Anderson, one of the workshop planning committee co-chairs, introduced the Day 2 agenda and session moderator, Dr. Peter Hennings (Bureau of Economic Geology, University of Texas at Austin). Chapter 2 captures the keynote presentation by Dr. Mark Zoback on the causes of earthquakes and induced earthquakes, the historical background to induced seismicity from fluid injection, the current state of understanding and occurrences of these events, and new research and collaborative approaches to manage the risk. Chapter 3 summarizes four of five panel presentations about developments in understanding induced seismicity in different regions of North America and specific research, technical, and regulatory challenges and advances related to mitigating and managing these kinds of events.3 The presentations included those of Dr. Tandis Bidgoli, Dr. Shawn Maxwell, Dr. Stuart Venables, and Dr. William Leith. Chapter 4 provides concluding remarks by the workshop co-chairs regarding induced seismicity and the entire workshop (Day 1 and 2). Supporting material in the appendixes includes: biographies of workshop presenters and moderators for Day 2 (Appendix B). Note that the biographies of the workshop planning committee and the list of workshop participants are available in the workshop proceedings from Day 1.
This proceedings of a workshop has been prepared by a rapporteur as a factual summary of what occurred at the workshop. The planning committee’s role was limited to planning the event. The statements made are those of the individual workshop participants and do not necessarily represent the views of all participants, the steering committee, the Roundtable on Unconventional Hydrocarbon Development, or the National Academies.
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3 Note that one panelist did not provide permission to summarize his presentation in this volume.
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