Introduction

This report provides an assessment of current and emerging water procurement and management technologies and practices related to shale energy development in the United States. Water resource management issues associated with shale energy development are of concern to policy makers because shale energy represents an opportunity as well as a challenge. Shale oil and natural gas present significant new energy resources, but their development also may pose risks to water quality and other water uses. The intersection of evolving technology, environmental protection, hydrocarbon energy demand, and national and geopolitical energy and trade interests provide the context for this study. Shale gas and shale oil (collectively referred to as shale energy ), which were long considered "unconventional" hydrocarbon resources, are now experiencing significant development in the United States. Economical extraction relies on directional drilling and hydraulic fracturing ("fracking"). This report discusses the water inputs to shale energy development, wastewater management related to shale energy development (including some related topics such as induced seismicity), and emerging water technologies for both the production of shale energy and the disposal of wastewaters. Primer on Shale Energy Resources Development

The extraction of shale energy has the potential to affect U.S. energy security by reducing quantities of crude oil and refined petroleum products purchased in global markets. The typical sources of water for well development have been surface or groundwater. Water quality also must be considered for compatibility with hydraulic fracturing. This is a potential disincentive for oil and gas operators to tap AMD from abandoned mines. The produced formation water can be highly saline, and often is referred to as produced brines. Proper storage and management of these fluids can prevent the potential contamination of groundwater and surface water that would occur if released into the environment. Many factors can influence the volume and management of shale gas produced fluids. Emerging Water Technologies for Shale Energy Development

The pace of technological change in water sourcing and water management for shale energy development is rapid, but uneven. Trends in water management have generally been influenced by local disposal costs, regulations, and geologic conditions, rather than by water scarcity alone. These include
nontoxic or "green" fracturing fluid additives , driven in part by concerns over the composition of fracturing fluids and increasing requirements of disclosure of fracturing fluid composition; alternatives to freshwater in the fracturing process , including recycled flowback fluids (mixed at various proportions with freshwater), carbon dioxide, nitrogen, hydrocarbon gases (such as ethane and propane), industrial waters, and (in the Appalachian region) potentially acid mine discharge waters; innovative well and well-pad configurations such as multilateral wells, which, in some cases, reduce the total volume of fluids required, but are more likely to have economic advantages in reducing labor, trucking, and other water handling costs; and closed-loop or reduced emission ( "green" ) well completions for handling flowback fluids and minimizing the venting of methane to the atmosphere. Widespread adoption of fracturing practices that minimize the use of freshwater (groundwater, surface waters, or municipally sourced waters) may reduce pressures from the shale energy sector on scarce water supplies in more arid areas such as Texas and the Rocky Mountain states. Water management issues are relevant to the entire life cycle of shale energy development, because fluids will continue to be produced even after a well is drilled, fractured, and producing oil and/or natural gas. Therefore, research that views shale energy production in a life-cycle and materials-flow context may facilitate the identification of technologies and processes that can mitigate potential impacts along different stages of the shale energy development life cycle.
Shale oil and gas (collectively referred to as shale energy), long considered "unconventional" hydrocarbon resources, are now being developed rapidly. Economic extraction of shale energy resources typically relies on the use of hydraulic fracturing. This technique often requires significant amounts of freshwater, and fracturing flowback and related wastewaters must be recycled or disposed of after a well is completed. While shale energy presents a significant energy resource, its development has the potential to pose risks to water availability and water quality.
This report provides a technological assessment of existing and emerging water procurement and management practices in shale energy-producing regions of the United States. The intersection of evolving technology, growing environmental concerns, demand for new sources of hydrocarbon energy, and the potential national interests in developing shale oil and gas resources provides the context for this study. Congressional attention has been focused on two key aspects of the issue: shale energy as a growing U.S. energy source, and environmental concerns associated with the development of these resources.
Water for shale energy projects is used most intensely in the fracturing portion of a well's life cycle. Under current practices, fracturing typically is a water-dependent activity, often requiring between a few million and 10 million gallons of water per fractured horizontal well. This water demand often is concentrated geographically and temporally during the development of a particular shale formation. Production activities and management and treatment of the wastewater produced during shale energy production (including flowback from fracturing and water produced from source formations) have raised concerns over the potential contamination of groundwater and surface water and induced seismicity associated with wastewater injection wells.
Water resource issues may pose constraints on the future development of domestic shale oil and gas. Potential negative effects from shale energy extraction—particularly effects associated with hydraulic fracturing and wastewater management—have prompted state and regional regulatory actions to protect water supplies. Future congressional and executive branch actions may influence development of shale oil and shale gas on federal lands and elsewhere through additional regulatory oversight or other policy actions. At the same time, advances in shale energy extraction and wastewater management techniques may reduce some development impacts.
The pace of technological change in water sourcing and water management in the shale energy sector is rapid, but uneven. Trends in water management have generally been influenced by local disposal costs, regulations, and geologic conditions rather than by water scarcity alone. Emerging technologies and practices in water resources management can be divided into those that seek to reduce the amount of consumptive freshwater utilization in the drilling and completion process, and those that seek to lower the costs and/or minimize the potential for negative environmental impacts associated with wastewater management.
Water management issues are relevant to the entire life cycle of shale energy development, because fluids will continue to be produced even after a well is drilled, fractured, and producing oil and/or natural gas. Research that views the shale energy production process in a life-cycle and materials-flow context may facilitate the identification of technologies and processes that can mitigate potential impacts along different stages of shale energy development.