Evolving Water Management Practices in Shale Gas Development
Soeder, Daniel J.; Rodriguez, Rebecca S.
Environmental concerns resulting from the large-scale development of shale gas have changed the way industry obtains, transports, recovers, and ultimately disposes of water. In the early years of shale gas development, water for hydraulic fracturing was largely obtained from municipal taps, resulting in public concerns about impacts on local drinking water supplies, especially in semi-arid locations like Texas. Drillers have since discovered that much cheaper water of far lower quality will work for hydraulic fracturing in most shales, and a combination of recovered flowback fluid and lower-quality water such as wastewater treatment effluent are now generally used. Transporting large volumes of water to well sites has also changed, where the current practice is to use a centralized impoundment to collect raw water and then send it to nearby well sites via a temporary, overland pipeline. This greatly reduces the number of tanker trucks driving on fragile dirt roads in sensitive stream headwater areas. Such improvements are largely the result of economics as well as regulations. However, some new problems have arisen. For example, disposal of high TDS flowback from the Marcellus Shale was initially done using a conventional wastewater treatment plant, which allowed the dissolved salts to pass through into freshwater streams, often resulting in fish kills. Regulatory changes and higher disposal costs have reduced this impact by encouraging drillers to recycle and dispose of their flowback water via Underground Injection Control (UIC) wells. This has resulted in a new problem of induced seismicity caused by large volumes of injected wastewater. Several new issues have come to light from recent research. These include the potential for the drilling process itself to create groundwater surges in shallow aquifers, entraining pre-existing methane gas, minerals, and sediment. This can affect the taste and appearance of groundwater in nearby water wells, and may increase methane concentrations to explosive levels. Another concern is that toxic metals and radionuclides associated with black shale may oxidize at the surface and leach from any drill cuttings left behind. These issues will need to be addressed by industry practice, regulations, or both, but as evidenced by previous challenges, they can also be viewed as opportunities to improve economics and public opinion.
AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013