Produced water
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Produced water is found in underground rock formations; the water is brought to the surface during oil and natural gas production. Produced water is found within the pores of rocks and reservoirs, and the content of produced water varies depending on the geological formation, the water's contact with hydrocarbons (the primary component of oil, coal, and natural gas), the water injected during previous oil and gas operations, and leftover chemicals in the water used during earlier oil and gas operations.[1][2]
Background
Produced water, which is found in the same rock formations as petroleum and natural gas, is brought to the surface during oil and gas production. Produced water can include naturally occurring water inside oil- and gas-bearing rock formations or contain water previously injected during oil and gas production. Water from rock formations adjacent to rock layers containing oil and gas may also be a component of produced water.[3][4]
The content of produced water varies. In general, produced water can contain the following elements:[5]
- Salt
- Oil and grease
- Inorganic and organic toxic compounds, which are used to improve drilling operations or found inside rock formations containing hydrocarbons like oil and gas
- Naturally occurring radioactive materials, which can leach into produced water from some rock formations.[3]
One type of produced water is known as flowback water. During unconventional oil and natural gas production (production that uses technology such as hydraulic fracturing to force petroleum or gas from the ground and up through a well), frac fluid containing mainly water and sand is injected into subterranean rock formations at high pressure. This activity produces a fracture network that allows crude oil and natural gas inside dense rocks to flow into a well and be extracted at the surface. A portion of the injected water returns to the surface and can contain part of the original water from the frac fluid as well as naturally occurring produced water underground.[3][5]
Management
Produced water can be managed in several ways. It can be injected back into formations to release more oil and gas or disposed into rock formations with no oil and gas. Some produced water is discharged into surface bodies of water; these discharges are regulated under the federal Clean Water Act. Portions of produced water may evaporate underground or at the surface, or some oil and gas operators may hire commercial disposal companies to collect and deliver the water to facilities for evaporation. Oil and gas operators can also reuse produced water in drilling and as frac fluid.[3][5]
Fracking background
- See also: 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
- ↑ The Institute for Energy & Environmental Research for Northeastern Pennsylvania, “What is flowback and how does it differ from produced water?” accessed January 27, 2014
- ↑ LMT Online, "Looking for water in the oil field," August 8, 2014
- ↑ 3.0 3.1 3.2 3.3 Advanced Water Technology Center, "About Produced Water (Produced Water 101)," accessed April 25, 2017
- ↑ Schlumberger, "Produced water," accessed April 27, 2017
- ↑ 5.0 5.1 5.2 Groundwater Protection Council, "U.S. Produced Water Volumes and Management Practices in 2012," accessed April 27, 2017
- ↑ 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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