What is hydrofracking?

Hydrofracking refers to hydraulic fracturing, a technique in which large amounts of water, combined with smaller amounts of chemicals and sand, are pumped under high pressure into a drilled gas well.  The purpose of hydraulic fracturing is to form tiny fractures in the rock by using water to force the rock to open along tiny existing fractures.  When the pressure is released and the water removed, the sand remains behind, propping open the newly created fractures and allowing gas to flow more freely into the well. For that reason, sand is called a proppant.

Hydrofracturing was first used in Kansas in 1947.  The Stanolind Oil Company injected a mixture of acid and oil into a well to stimulate production of oil.  A patent was issued the following year, and Halliburton Oil Well Cementing Company was given the exclusive rights to using the fracturing method.  Halliburton added sand to the oil mixture and began fracturing wells.

Initially, oil and other more viscous (thicker) materials were pumped into wells to complete a fracturing job.  In 1953, water was introduced as a fracturing fluid, and various chemicals have been added over the years to increase the effectiveness of the fluid.  Along with testing the usefulness of many chemicals, different kinds and sizes of proppants were tested for effectiveness.  The first jobs were completed using sand, but materials tested have also included plastic pellets, steel shot, resin-coated sand, and various metal beads.  While the concentrations of sand in the first hydraulic fracturing attempts were limited by the low pressure of pumps, the ability to use very high pressure has allowed current fracturing jobs to use much higher concentrations of sand.  Higher pressure and concentrations mean that more fractures are able to be opened and more gas to be released from the well.

Though exact fracturing methods and materials may vary from well to well,  most wells wells are fractured from eight to forty times during their lives.  Some estimates claim that hydraulic fracturing has allowed for a more than 90 percent  increase in recovering natural gas when compared to production of wells in which hydrofracking was not employed.   However, concerns have been raised regarding the treatment of the resulting wastewater that is produced by the hydrofracking process, as well as the safety of the chemicals used to make the hydrofracking fluid. 

Primary Author: Rachel Curtis ---- Posted: 14 January 2011 ---- Version: Revision #1, 26 March 2011

Suggested citation style: Curtis, R. 2011. What is hydrofracking?  Institute for Energy and Environmental Research of Northeastern Pennsylvania Clearinghouse website. http:energy.wilkes.edu/156.asp. Posted 26 March 2011.