Production of oil and gas is often accompanied by production of water from the same formation. In recent years, water has been injected into wells in the process known as hydraulic fracturing, or “fracking.” Much of the frac water returns with oil and gas during the initial production of the fracked well. Fracking of horizontal wells requires huge quantities of water, and when this water—and water native to the formation—returns to the surface, something must be done with the water.
Historically produced water has been treated as waste—a substance that contains not only water but also salts, chlorides, sodium, carbon dioxide, and heavy metals. Produced water has typically been disposed of by injection into underground formations. Well operators may drill their own disposal wells or may contract with third parties to dispose of produced water for a fee.
Water used in fracking has typically been obtained from formations containing fresh groundwater. The huge quantities of fresh water used for fracking have taxed some aquifers, and the practice has been criticized as wasting a precious resource.