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Introduction

Oil and gas well completion and stimulation technologies to develop unconventional hydrocarbon resources in the United States have evolved over the past several decades, particularly in relation to the development of shale oil and shale gas. Shale oil and shale gas resources and the technology associated with their production are often termed “unconventional” because the oil and gas trapped inside the shale or other low-permeability rock formation cannot be extracted using conventional technologies (NRC, 2014). For the low-permeability oil and gas reservoirs, other technologies, such as those combining horizontal drilling with hydraulic fracturing are required to stimulate the flow of oil or gas to the well bore (NASEM, 2017). Since about 2005, the application of these technologies to fields in the U.S. have helped produce natural gas and oil in volumes that allowed the country to reduce its crude oil imports by more than 50% and to become a net natural gas exporter.¹ Some reservoirs, for example, the Mississippian Limestone Play in Oklahoma and Kansas, are largely conventional,² but have also benefitted from use of unconventional technologies. The regional and national economic and energy advances gained through production and use of these resources have been accompanied, however, by rapid expansion of the infrastructure associated with the development of these fields and public concern over the impacts to surface- and groundwater, air, land, and communities where the resources are extracted.

The intent of the first day of the workshop of the National Academies of Sciences, Engineering, and Medicine’s Roundtable on Unconventional Hydrocarbon Development, held on December 1, 2016, was to discuss onshore unconventional hydrocarbon development in the context of potential environmental impacts and the ways in which the risks of these kinds

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¹ See https://www.eia.gov/todayinenergy/detail.php?id=29433 (accessed September 2017).

² A conventional hydrocarbon reservoir is one in which the hydrocarbons are generally maintained in place by buoyant forces below a tight caprock and the reservoir rocks are pressurized above hydrostatic pressure due to compaction of the sedimentary rocks over time. When penetrated by a well bore, the fluids in the pressurized sedimentary rock flow to the surface until the pressure in the reservoir returns to hydrostatic conditions (NRC, 2013; Schlumberger Oilfield Glossary, http://www.glossary.oilfield.slb.com/Terms/c/conventional_reservoir.aspx (accessed December 2017)).

of impacts can be managed (see Box 1.1 for statement of task). Specifically, the workshop sought to examine the lifecycle development of these fields, including decommissioning and reclamation of wells and related surface and pipeline infrastructure, and the approaches from industry practice, scientific research, and regulation that could help to ensure management of the operations in ways that minimize impacts to the environment throughout their active lifetimes and after operations have ceased. From the standpoint of the workshop, discussions were oriented toward mitigating the possibility of leaving “negative legacies” in the environment in regions of the country where this type of oil and gas development has been occurring. The workshop focused on identification and comparison of different technical, scientific, and regulatory approaches that are employed in these regions and the ways in which those approaches have been or could be applied to manage potential environmental risks. Workshop presentations and discussion addressed existing data and information needs and gaps, regulatory drivers, and monitoring and assessment needs.

WORKSHOP OVERVIEW AND OBJECTIVES

This proceedings of a workshop has been prepared by the rapporteur as a factual summary of what occurred at the workshop. The planning committee’s role was limited to planning and convening the workshop (see Appendix A for the agenda and Appendix B for the biographies of the planning committee members). The views contained in the report are those of individual workshop participants and do not necessarily represent the views of all workshop participants, the planning committee, or the National Academies of Science, Engineering, and Medicine. The workshop was organized around topics outlined in the statement of task (Box 1.1).

Following welcoming remarks by Drs. David Dzombak and Wendy Harrison, co-chairs of the Roundtable, Drs. Julia Haggerty and Brian Anderson, the workshop planning commit-

tee co-chairs, described the genesis and focus of the workshop. Dr. Haggerty characterized onshore oil and gas development in the United States as proceeding with a “learn-as-you-go” approach and fast pace. When the Roundtable first convened in December 2015, the Roundtable members recognized that the reduced pace of onshore development activities due to lower oil and gas prices offered a learning opportunity around different issues associated with the development of unconventional resources. The longer-term environmental risks that different regions in the United States may face as a result of unconventional oil and gas development was one topic identified by the members as being appropriate for a broad discussion among experts from different sectors. The Roundtable suggested convening this workshop around a conversation that characterized assets and risks embodied in deploying and operating unconventional oil and gas infrastructure and identified what is known and unknown about potential negative environmental legacy issues associated with development of the resources. Haggerty noted that the focus of the workshop’s first day was on identifying, framing, and describing opportunities and challenges to ensure successful decommissioning, reclamation, and long-term stewardship of unconventional oil and gas fields, particularly related to land and water resources. The second day of the workshop would consider fluid injection and its relationship to induced seismicity.³

Dr. Anderson emphasized three outcomes the workshop might achieve:

• Convening a group of experts with ample opportunity for audience participation and engagement on issues;
• Leveraging the diverse knowledge in the room and sharing discussion at the interface of the technical information and stakeholder experience; and
• Identifying knowledge gaps and follow-up activities.

Chapter 2 summarizes keynote presentations for understanding legacy issues and managing risk. Chapters 3 through 5 summarize panel presentations and the moderated discussions. Chapter 3 focuses on infrastructure, environmental restoration and management. Chapter 4 covers observation, monitoring, and changes in technology. Chapter 5 describes the intersection of technology and regulation. Chapter 6 includes concluding remarks by workshop co-chairs followed by a facilitated discussion. Supporting material is provided in the references and appendixes. Appendix C provides biographies of the presenters and moderators; Appendix D is a list of the Roundtable members and Appendix E is a list of workshop participants.

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³ The second day of the workshop is being published as a separate workshop proceedings.

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