RIASSUNTO
Abstract
Exploration, drilling and production of shale gas plays such as the Barnett, Marcellus, Fayetteville, and Haynesville have transformed the unconventional gas industry. These and other existing and developing plays have had significant positive economic impacts to many regions, created tens of thousands of jobs, and have generated royalty and tax payments to a variety of state and local governments as well as many individuals. At the core of shale gas development are two key technologies: horizontal drilling and hydraulic fracturing. Techniques used to hydraulically fracture horizontal wells completed in shale reservoirs often require three to seven million gallons of water per well. The rapid development of shale gas across the country has resulted in a substantial discussion of water issues such as the impacts of water withdrawal, and disposal of produced water. Because of the rapid increase in shale gas development, the concerns about these issues have focused more and more on cumulative impacts of these activities. This paper will explore the considerations and challenges involved when examining the potential cumulative impacts from different water sourcing options, including low-quality water sources, and from different ways of managing produced water, such as underground injection, treatment through commercial and public treatment facilities, disposal and reuse. Basin-specific situations and factors will be discussed.
Introduction
Shale gas development has become prominent due to two key technologies: horizontal drilling and hydraulic fracturing. The drilling and hydraulic fracturing of a horizontal shale gas well requires water volumes ranging from two to seven million gallons of water per well, depending on the formation characteristics, but the volume needed may vary substantially between wells (ALL Consulting and GWPC 2009). The water frequently comes from surface water bodies such as rivers and lakes, but can also come from groundwater, private water sources, municipal water, and re-used produced water. Growing populations, other industrial water demands, and seasonal variations create challenges for shale gas operators to find water sources that meet the needs for development while satisfying the regional water demands.
While the water needed to drill and hydraulically fracture a well appears large, it is typically a small percentage of the cumulative water use in any given shale basin (See Table 1) (Arthur, Uretsky, and Wilson 2010). Industrial, municipal, and commercial water users typically use water year-round while shale gas operators require procurement for a short period. Although the demand for water in drilling and hydraulic fracturing for each well is short-term, withdrawals may stretch over a period of time prior to development to ensure that the total amount of needed water is readily available when operations commence.
This paper will examine the challenges that shale gas operators face in finding suitable water sources for drilling and hydraulic fracturing while sustaining the demands for regional water needs. In addition, the challenges associated with the management of the produced water will be discussed and the paper will conclude with a discussion on the cumulative impacts associated with water sourcing and management.
Water Sourcing Challenges
Water used in drilling and hydraulic fracturing can come from surface water, groundwater, municipal and industrial sources, and reused water from other sources such as previous hydraulic fracturing operations (Veil 2010). Water withdrawals from those sources have led non-governmental organizations (NGOs), politicians, government agencies, and the public to express concerns regarding the associated environmental implications. Additional considerations in evaluating water needs for a project include the location of the need, the seasonal timing of the need, the location of available water, and the regulations governing water withdrawals.