Gas Production Technique Under Scrutiny

Controversy Over Whether Drilling Fluids are Contaminating Groundwater

About 90 percent of natural gas wells now employ hydraulic fracturing, a technique in which sand and fluids are pumped into wells to open seams within rock formations so that they release more methane. This practice, commonly called “fracking,” has allowed for the production of gas from formations one to two miles deep, and is credited with more efficient development of gas reservoirs with fewer wells. It is also considered critical to economical production from

shale formations, such as the Marcellus Shale region in the Eastern U.S., which tend to feature low porosity rock.

In fracking operations, wells are completed to the desired depth and the bottom portions of the well casing are punctured with explosive charges, releasing pressurized water and sand into resulting fractures in the rock. The water contains an estimated one percent drilling fluids, primarily lubricants and surfactants. The precise formulations of these fluids are proprietary, but constituent chemicals may include benzene, zetaflow ® (whose composition is not publicly known) and 2-butoxyethenol (2-BE).

It is these drilling fluids that have aroused complaints from neighboring landowners and environmental advocates, who claim that they are polluting groundwater near gas wells. These parties cite odors, coloring and sediments observed in tap water, as well as isolated cases of illness. They also call for the identity of the fracking fluids to be revealed, without which linkages to water contaminants will be difficult to establish.

A 2004 EPA study on coalbed methane production concluded that it was unlikely to impact groundwater because water tables resided hundreds or thousands of feet above the fractured portions of wells. Some advocates of further study and regulation acknowledge this, but theorize that imperfections in well structures may be allowing fracking fluids up into the well shaft and from there onto the surface and the groundwater beneath.

Based in part on EPA’s work, Congress in 2005 exempted fracking fluids from the Safe Drinking Water Act, which requires the disclosure of chemicals potentially released into groundwater. Legislation proposed by Rep. Diana DeGette (D-CO) and Charles Schumer (D-NY) would revoke that exemption and thereby shed light on the compounds being used. These bills are supported by the Natural Resources Defense Council (NRDC) and other public interest groups.

EPA has announced another review of the issue, and has asked nine leading drillers to voluntarily provide the agency with the formulations of their fluids. A coalition of state water regulators is also promoting voluntary disclosure of fluid components, which it plans to post on a website for the benefit of researchers.