THE FATE OF PETROLEUM RELEASES FROM THE
OSAGE-SKIATOOK PETROLEUM ENVIRONMENTAL
RESEARCH (OSPER) SITES, OSAGE COUNTY, OKLAHOMA
Frances Hostettler*
Edward M. Godsy
Yousif K. Kharaka
U. S. Geological Survey
345 Middlefield Rd.,
Menlo Park, CA 94025
Voice: 650-329-4584
Fax: 650-329-4538
E-mail: fdhostet@usgs.gov
We are involved in a multidisciplinary investigation to study the transport, fate, natural attenuation and impacts of hydrocarbons, inorganic salts, trace metals, and radionuclides present in petroleum and produced-water releases at the OSPER A and B sites, located adjacent to the 4250-hectare Skiatook Lake, that provides drinking water to local communities and is a recreational fishery. More than one hectare of land at each site is affected by salt scarring, soil salinization and brine and petroleum contamination. Petroleum wells at the A site are inactive; the bulk of the hydrocarbon (now degraded and weathered oil) and produced water releases occurred 65-90 years ago. The B site includes an active production tank battery and adjacent brine and oil pit, an inactive tank battery and an injection well with a small brine pit. For this study, oil, soil, gas and/or water samples were obtained from several oil wells located at and adjoining the sites, from active pits at the B site, from inactive pits and surface accumulations at the A site and from several of the 60 boreholes, that are 1-71 m deep. Characterization of the resident microbial populations was completed for a number of these samples.
Results show that the local source oils are paraffinic-naphthenic light crude, containing n-alkanes as the dominant components. These oils, though obtained from shallow (300-600 m depth) sandstones, are not significantly impacted by biodegradation, probably because of the high salinity (~150,000 mg/L total dissolved solids) of the associated brine. The oils at the inactive A site are similar to each other although they do vary widely in stages of biodegradation. Some nearby oils at the active B site do not correlate with other site B oils, suggesting that there is not significant subsurface transport of the spilled oils. Microbial populations at both sites are degrading the water-soluble crude oil compounds. Concentrations of organic species, Fe, Mn, SO4, and other geochemical evidence, and make-up of the microbial populations at both sites indicate that the systems are slightly different but based on free energy yields, are both poised at the level of iron reduction.