Hydro-fracturing

From Wikimarcellus

Hydro-fracturing, or fracing for short, is the process of injecting water, sand, diesel fuel, and/or a cocktail of chemicals into a well, under high pressure, in order to fracture the shale thereby releasing methane gas trapped in the pores of the rock so it can flow up the pipe. It may be accompanied by acid fracturing and the use of proppants. Also crosslinked guar gel is sometimes used. Generally, the nature of chemicals used for the purpose of freeing gas trapped in shale are tightly held trade secrets by the various drilling companies. Many of the chemicals are believed to be toxic substances.

Worker adjusting water line used in hydro-fracturing
a Marcellus well in Dimock Township, Susquehanna County
Courtesy of Michael J. Mullen, Staff Photographer,
Scranton Times-Tribune[1]

While the hydro-fracturing process can use millions of gallons of water for a well, typically wells use around 750,000 gallons. It generates similar quantities of waste water. The fluid that comes back up is called flowback. Water usually must be trucked into and out of a well site.

One method of hydro-fracturing is slickwater, which reportedly involves injecting friction reducers, biocides, surfactants and scale inhibitors. For example methanol and naphthalene can be used for biocides. Hydrochloric acid and ethylene glycol may be utilized as scale inhibitors. Butanol and ethylene glycol monobutyl ether (2-BE) are used in surfactants.

Many environmentalists have raised concerned about this process as a potential source of toxic contamination of the water supply. It also requires millions of gallons of water which usually must be trucked into drilling sites. The tanker trucks used to bring water in and diesel engines used to power drilling and pumping equipment on the drill site are recognized as a sources of air pollution. There are also concerns about noise-control issues. These relate not only to noise from drilling and pumping equipment, but also from gas compressors which run continuously once the well is actually producing gas.