EVALUATING THE IMPACT OF OIL AND GAS WASTEWATER DUMPS IN THE PERMIAN BASIN ON SOIL BIOGEOCHEMISTRY

Over the past decade, increasing U.S. oil and gas (OG) production has been accompanied by production of large volumes of wastewaters (~14 billion barrels per year), which require disposal. The most common disposal practice is injection into geologic reservoirs for water flooding, pressure maintenance, or into underground disposal wells. However, spills or illegal dumping of OG wastewaters are of environmental concern given their complex chemistry including high total dissolved solids, elevated radium, drilling and production chemicals, and presence of organic constituents. Despite these concerns, little is known about the environmental effects of OG wastewater spills on arid lands. We focus on a series of over 39 illegal OG wastewater dumps in the Permian Basin that started in November of 2017, which released approximately 4,000 barrels of OG drilling and production wastewaters. We sought to 1) identify whether spilled OG wastewaters came from conventional gas vs. tight oil vs. conventional oil reservoirs, and 2) evaluate environmental impacts resulting from OG wastewater spills. Approximately 4 months after the dump sites were identified and mapped, soils from unaffected (control) and affected (dump) zones were sampled from a total of 7 dump sites. Soil conductivity and extractable salts were higher in dump zones compared to areas outside of the dump zones at all locations, with conductivity within the dump zones ranging from 1 to 167 mS/cm. Extractable salts in all dump zones reflected the composition of local OG wastewater from deep basin brines, e.g., enriched in Na, Cl, B, indicating that the wastewater was not from conventional OG reservoirs. Hg concentrations were elevated in spill-affected soils compared to controls, but concentrations were low overall (< 12 ng/g dry wt.). Soil microbial communities were characterized to assess ecological effects and had lower diversity and shifts in taxonomic composition in dump zones compared to control areas. Together, these results will be used to assess the impact of OG wastewater constituents on soil biogeochemistry and potential for long-term environmental impacts.