A salt water disposal well (SWD) is a specialized underground injection well used by the oil and gas industry to safely dispose of produced water — the salty, mineral-laden water that comes up from the ground along with oil and natural gas. This water is often far saltier than seawater and may contain hydrocarbons, metals, and naturally occurring radioactive material, making surface disposal unsafe and impractical.

In an SWD operation, the produced water is transported by pipeline or truck to the well site, filtered, and then injected thousands of feet underground into deep geological formations that are isolated from freshwater aquifers by thick layers of impermeable rock. These formations have held fluids for millions of years and are selected specifically because they can safely accept and contain the injected water without migration.

SWD wells are heavily regulated and continuously monitored. They play a critical role in modern energy production by allowing operators to maintain reservoir pressure, manage large volumes of produced water, protect surface and groundwater resources, and comply with environmental regulations — all while enabling continued oil and gas development.