|Well drilling in Leroy Township, PA.|
Drillers are Chesapeake Energy.
Photo by C.J. Marshall published in
The Daily Review.com
What is fracking? Some will know already because it was the subject of the hit movie "Gasland" last year. It is a controversial process that pits the needs for gas resources against the needs for a clean environment, in this case, particularly, the needs for clean water. "Fracking" is a popular term used for "fracturing" of rocks for the purpose of improving the recovery of oil and gas from subsurface reservoir rocks. It is not a new technique, having been around since the late 1940's when Haliburton introduced it. A version of it was explored extensively in the 1980's and 1990's as a way to circulate fluids in warm areas of the crust to bring geothermal heat to the surface. "Fracking" occurs naturally in the earth when fluids, such as magma, create pressure in the rocks to create dikes and sills, though the term is not used by geologists in this context.
During fracking, fluid is pumped into a well bore at a pressure that cause the rocks hosting the well to fracture. In order to keep the fractures open after the injection of the fracturing fluid, a substance referred to as the "proppant" is added to the fracture fluid. This is often sand that has been chosen to have a shape and size that will have high permeability.
Fracking is in the news a lot now because of the urgent need for the US to produce its own coal and gas, and a rich reservoir of gas-containing rocks is the Marcellus Formation, a shale that extends through much of the Appalachian Basin in Pennsylvania and New York State. There is an excellent resource here if you are interested in details from the state of New York.
The controversial part of fracking is related to the nature of the fluids injected. Fluids range from water to gels, foams, and sometimes, even gases such as air, nitrogen, or carbon dioxide. Additives are numerous, as evidenced by this list of those allowed in New York State. (I took this list from the Wiki article on fracking, and it is an extensive article for further materials.)
|CAS Number||Chemical Constituent|
|2634-33-5||1,2 Benzisothiazolin-2-one / 1,2-benzisothiazolin-3-one|
|10222-01-2||2,2 Dibromo-3-nitrilopropionamide, a biocide|
|15214-89-8||2-Acrylamido-2-methylpropane sulphonic acid sodium salt polymer|
|67-63-0||2-Propanol / Isopropyl Alcohol / Isopropanol / Propan-2-ol|
|26062-79-3||2-Propen-1-aminium, N,N-dimethyl-N-2-propenyl-chloride, homopolymer|
|9003-03-6||2-propenoic acid, homopolymer, ammonium salt|
|25987-30-8||2-Propenoic acid, polymer with 2 p-propenamide, sodium salt / Copolymer of acrylamide and sodium acrylate|
|71050-62-9||2-Propenoic acid, polymer with sodium phosphinate (1:1)|
|66019-18-9||2-propenoic acid, telomer with sodium hydrogen sulfite|
|107-19-7||2-Propyn-1-ol / Propargyl alcohol|
|127087-87-0||4-Nonylphenol Polyethylene Glycol Ether Branched / Nonylphenol ethoxylated / Oxyalkylated Phenol|
|68442-62-6||Acetic acid, hydroxy-, reaction products with triethanolamine|