Assessing Freshwater Threats from Oil and Gas Drilling on the Tallgrass Prairie Preserve in Oklahoma

The 40,000-acre Tallgrass Prairie Preserve is located in Osage County, in northeastern Oklahoma.  All of the mineral rights for the 1.47M-acre Osage County are held in trust by the US Government for the Osage Nation, with mineral rights being superior to surface rights. The preserve is located in the upper reaches of the Sand Creek watershed which flows northwest to southeast across the preserve. Six additional streams are located on the preserve as well. There are over 200 conventional oil and gas wells on the Tallgrass Prairie Preserve. In 2012, three unconventional oil wells were drilled vertically to a depth of 2,500 feet, and then drilled 3,000 feet horizontally.  An estimated 1,920,000 to 2,560,000 gallons of water was used from groundwater located on the preserve to drill and then hydraulically fracture each unconventional well bore. A drilled disposal well was used to re-inject the salty-brine water underground at 4,000 to 5,000 feet, so no recycling of water is occurring. Declines in fish species that were intolerant to habitat and water quality changes occurred between 1991 and 2013. The Nature Conservancy is assessing the possible impacts of oil and gas drilling and what the potential effects might be on the freshwater ecosystem.