Slick water frac
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Slick water frac is a type of frack fluid—a combination of water, chemicals, and sand that is injected into a crude oil or natural gas well to reduce friction pressure and create a fracture. During hydraulic fracturing (also known as fracking), fluid is injected at a high speed into a wellbore to enhance the release of oil or natural gas located under the earth.
The chemical composition of slick water frac fluid can vary depending on the geological features near the area being fractured. On average, frac fluid contains between 98 percent and 99.5 percent water and sand. Between 0.5 percent and 2 percent of the fluid is composed of chemical additives, which are used to stop the growth of microorganisms, prevent well casing corrosion, increase the rate at which the fluid is injected, and reduce pressure, among other things. The water is used in part to transport the chemicals and sand—the latter two of which are chosen to ease the production of oil or gas—from the wellhead to the bottom of the well to increase the well's production of oil and gas.[1][2]
Background
Frac fluid consists of water, sand (or another type of proppants, which are used to prop open fractures), and chemical additives. The additives are used to increase the amount of oil or gas extracted from the well. The type and amount of chemical additives and proppants depend on the geology of the area around the well. Oil and gas operators use non-viscous (non-thick) slick water frac fluid to create narrow fractures with fewer proppants. Oil and gas operators use slick water fracking fluid in the Barnett Shale region in Texas and the Marcellus Shale region in Pennsylvania to create more complex fractures from which to extract oil and natural gas.[2][3]
A common chemical additive in slick water frac fluid is a friction reducer, which lowers friction pressure to moderate pumping pressures to a more manageable level. Other chemicals in slick water fluid include the following:[4]
- Disinfectants are used to limit the growth of microbes that can break down frack fluids. Similar disinfectants used during fracking are used in hospitals, municipal water systems, and over-the-counter skin antiseptics.
- Surfactants are used to lower surface tension.
- Thickeners, also known as gelation chemicals, are used in hybrid frack fluids to transport proppants to prop open fractures.
- Scale inhibitors are used in varying amounts depending on the shale formation to prevent a build-up of minerals in the inner wall or casing of a well.
- Hydrochloric acid is used at some sites to reduce pressure when shale rock is first cracked. The acid is used in the earlier stages of drilling, typically in the first inches of the rock.
- Corrosion inhibitors are organic compounds used in fracking to protect casing and equipment from corroding.[5]
Overview of fracking
Hydraulic fracturing, also known as fracking, is a method of oil and natural gas extraction. The process involves injecting fluid into subterranean rock formations at high pressure. The high-pressure fluid produces a fracture network that allows crude oil and natural gas inside dense rocks to flow into a wellbore and be extracted at the surface. The fluid (known as frac fluid) contains between 98 percent and 99.5 percent water and sand; between 0.5 percent and 2 percent of the fluid is composed of chemical additives, which are used to stop the growth of microorganisms, prevent well casing corrosion, increase the rate at which the fluid is injected, and reduce pressure, among other things.[6]
According to the U.S. Energy Information Administration (EIA), there were approximately 23,000 hydraulically fractured wells in the United States in 2000. In 2015, the United States contained approximately 300,000 hydraulically fractured wells, accounting for 67 percent of U.S. natural gas production and 51 percent of U.S. crude oil production.[7][8][9]
See also
Footnotes
- ↑ ALL Consulting, "Hydraulic Fracture Considerations for Natural Gas Wells of the Marcellus Shale,” accessed January 28, 2014
- ↑ 2.0 2.1 Geology.com, "Hydraulic Fracturing Fluids - Composition and Additives," accessed June 28, 2016
- ↑ PetroWiki, "Fracturing fluids and additives," accessed June 29, 2016
- ↑ PetroWiki, "Fracturing fluids and additives – Overview," accessed March 27, 2015
- ↑ Society of Petroleum Engineers, “Hydraulic Fracturing 101: What Every Representative, Environmentalist, Regulator, Reporter, Investor, University Researcher, Neighbor and Engineer Should Know About Estimating Frac Risk and Improving Frac Performance in Unconventional Gas and Oil Wells,” accessed January 30, 2014
- ↑ Frack Wire, “What is Fracking,” accessed January 28, 2014
- ↑ University of Oklahoma, "Hydraulic Fracturing and Water Resources," accessed March 12, 2014
- ↑ U.S. Energy Information Administration, "Hydraulic fracturing accounts for about half of current U.S. crude oil production," March 15, 2016
- ↑ U.S. Energy Information Administration, "Hydraulically fractured wells provide two-thirds of U.S. natural gas production," May 5, 2016
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