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Environmental impacts of petroleum production: 2- The fate of inorganic and organic chemicals in produced water from the Osage-Skiatook Petroleum Environmental Research site A, Osage County, Oklahoma

James J. Thordsen
Yousif K. Kharaka
Gil Ambats
U. S. Geological Survey
Menlo Park, CA 94025

Presented at the 9th International Petroleum Environmental Conference
Special Session: Fate And Transport Of Brine And Hydrocarbon
Releases In Soils and Water, Northeast Oklahoma
Albuquerque, New Mexico, October 22-25, 2002

Full Text of the Paper (1.54 MB)

Abstract

We are involved in a multidisciplinary investigation to study the transport, fate, and natural attenuation of inorganic salts, trace metals, radionuclides and organic compounds present in produced water, and their impacts on soil, surface water and ground water and the local ecosystem at the Osage-Skiatook Petroleum Environmental Research (OSPER) sites A and B, located in Osage County, OK. At site A, about one hectare of land is affected by salt scarring, soil salinization and brine and petroleum contamination from accidental releases of produced water and associated hydrocarbons from brine pits, tank batteries and broken pipes. Most petroleum wells and tank batteries at site A have been inactive for decades and most of the produced water and hydrocarbon (now degraded and weathered oil) releases occurred more than 60 years ago. However, one pit at this site contains relatively fresh asphaltic oil and high salinity brine. The local geology and hydrology indicate that the bulk of inorganic salts and some dissolved organic species in the released brine reach the adjacent Skiatook Lake, a 4250-hectare reservoir that provides drinking water to the local communities and is a major recreational fishery.

For the OSPER site A study, 25 water samples were obtained from oil wells adjoining site A, from the asphaltic pit and adjacent weathered-oil pit, from a local stream channel and the Skiatook Lake, and from 12 of 24 boreholes (1-35 m deep), recently drilled and completed mostly within the impacted area. Results to date show that the produced water source was a Na-Ca-Cl brine (~150,000 mg/L total dissolved solids), with relatively high concentrations of Sr, Mg and NH4, but low SO4 and H2S. With the exception of Fe and Mn, the concentrations of trace metals are low. The salinity of water obtained from the asphaltic pit is comparable to that of the produced water source. The salinity of water obtained from the boreholes in the impacted area, however, is much lower, reaching a value of only about 15,000 mg/L total dissolved solids in water from a borehole located on land that is normally covered with lake water. Chemical and isotope analysis of the collected samples, water level monitoring and additional sampling are continuing. Results to date clearly show that significant amounts of salts from produced-water releases still remain in the soils and rocks of the impacted area after more than 60 years of natural attenuation.


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