The Wyoming State Geological Survey has published a study of groundwater salinity in the Wind River Basin.
It is the final study in a series examining water quality in energy-producing basins in Wyoming – like the Wind River Basin, which produced 2.62 million barrels of oil and 79 billion cubic feet of gas in 2019, according to the WSGS.
That same year, the Wind River Basin produced almost 236.5 million barrels of water, while averaging 6-10 inches of precipitation for a population of about 40,000 people, the study states.
“The oil and gas industry uses substantial amounts of water to drill new wells during exploration while coproducing large volumes of saline groundwater during production,” the WSGS said, suggesting that, in areas where exploration and production operations are both under way, it might me “cost-effective” to use that produced saline water for new well drilling and development.
The method would conserve freshwater resources while also managing the “often-substantial volumes of coproduced water,” which is “not suitable for other beneficial uses,” WSGS said.
Salinity refers to the concentration of dissolved minerals in water, the WSGS said, and it is only a “general predictor of water quality” since it doesn’t specify the chemical constituents involved.
“Groundwater with low (salinity) can contain toxic concentrations of manufactured chemicals such as pesticides or naturally occurring heavy metals and radioactive elements,” the WSGS said. “Still, salinity is a useful measure of general water quality.”
The Wyoming Department of Environmental Quality sets maximum salinity for domestic water at 500 milligrams per liter, the study states, but the limit rises to 2,000 mg/L for irrigation, 5,000 mg/L for livestock, 10,000 mg/L for some industrial uses and more than 10,000 mg/L for others.
In the Wind River Basin, the WSGS said industrial-grade water, with a salinity of more than 5,000 mg/L, makes up “more than 50 percent of groundwaters at depths greater than 5,000 feet below ground surface but are less prevalent at shallower depths.”
Most groundwater with that level of saline in Wyoming is produced from oil and gas wells that are more than 1,000 feet deep, the WSGS said.
For more information visit the WSGS website.