Produced water is a term used in the oil industry to describe water that is produced as a byproduct along with the oil and gas.
The petroleum industry, also known as the oil industry or the oil patch, includes the global processes of exploration, extraction, refining, transporting, and marketing of petroleum products.
Oil and gas reservoirs often have water as well as hydrocarbons, sometimes in a zone that lies under the hydrocarbons, and sometimes in the same zone with the oil and gas.
Oil wells sometimes produce large volumes of water with the oil, while gas wells tend to produce water in smaller proportion.
To achieve maximum oil recovery, waterflooding is often implemented, in which water is injected into the reservoirs to help force the oil to the production wells.
In the oil industry, waterflooding or water injection is where water is injected into the oil field, usually to increase pressure and thereby stimulate production.
The injected water eventually reaches the production wells, and so in the later stages of waterflooding, the produced water proportion of the total production increases.