SUMMARY OF PERMITTED LAND APPLICATION OF DRILLING FLUIDS FROM OIL AND GAS WELLS IN OKLAHOMA

Spent drilling fluids are a waste product generated during drilling of unconventional oil and gas wells prior to hydraulic fracturing or production of energy resources from wells. These fluids are exempted from federal hazardous waste regulations but could pose environmental or human health risks due to the residual salt and petroleum hydrocarbons they contain. State regulations for disposal of drilling fluids vary; regulations commonly allow for on-site burial or transportation to off-site landfills. Some States, such as Oklahoma, permit drilling fluids to be spread and tilled into the land surface, allowing for natural attenuation of contaminants. Land application of these wastes typically occurs on private land near drilling sites to realize cost savings in transportation. While landowners are financially compensated for land application, the benefits or risks involved are not well studied. Additionally, the scope and scale of the land application of drilling wastes is unclear.

In Oklahoma, the permit records for land application of drilling wastes are publicly available in scanned documents. We assembled 7,023 permit records into a more usable spreadsheet format at the statewide level for the years 2000, 2005, 2010, and 2015, and for the Upper Washita River watershed for 1998-2020. Permit-specific data are valuable for quantifying and understanding the locations and quantities of land-applied drilling fluids and to assess potential environmental effects. Information assembled includes dates, locations, number of acres and volumes of liquids and solids applied, and soil conductivity prior to land application.

Based on the assembled statewide data, 5,836 to 44,000 acres per year receive drilling wastes and approximately 1.0 to 10.6 million barrels of liquid and 0.5 to 4.4 million barrels of solid drilling wastes are applied per year. In the Upper Washita River watershed, a total of approximately 81,000 acres have received drilling wastes, or 4 percent of the total watershed area. The assembly of these data facilitates a better understanding of the quantity and spatial extent of the land application of spent drilling fluids and provides valuable information to evaluate the proximity of this practice to sensitive environmental areas and populations.