HYDROLOGY AND SUBSURFACE TRANSPORT OF OIL-FIELD
BRINE AT THE OSAGE-SKIATOOK PETROLEUM
ENVIRONMENTAL RESEARCH "A" SITE, OKLAHOMA
William N. Herkelrath*
Yousif K. Kharaka
U.S. Geological Survey
345 Middlefield Road, MS 496
Menlo Park, CA 94025
Voice: 650-329-4625
Fax: 650-329-5590
E-mail: wnherkel@usgs.gov
As a part of a multidisciplinary study of the impact of oil wells and oil production on the environment, we are investigating the hydrology of the depleted OSPER "A" site, which is located at Skiatook Lake in Osage County, Oklahoma. Contamination of soil, ground water, and surface water at this site from crude oil and brine produced from oil wells is extensive today, over 60 years after oil production ceased. We drilled 44 wells at the site for ground-water sampling and hydraulic testing. Cores from the well bores indicate there are relatively thin (<2 m thick) permeable sandstone beds separated by thicker shale and mudstone confining units. Water samples from the wells indicate there is an extensive subsurface plume of salt water (2,000-30,000 mg/L TDS) down slope from the former oil and brine handling facilities. Continuous water pressure monitoring indicates well water levels respond rapidly to changes in barometric pressure, and the wells have high barometric efficiency. There is little response to rainfall, suggesting recharge is slow. Slug tests run on the wells indicate the hydraulic conductivity of the permeable sandstone units is only about 1 cm/day. These results are consistent with the conceptual model that the brine is present in relatively low permeability, confined sandstone beds. We hypothesize that when oil production was active, a large volume of brine infiltrated from storage ponds and channels located on top of the sandstone, and moved down slope in the sandstone beds. Once the source was removed, recharge and flow through the salt plume zone was greatly reduced, effectively trapping the salt water in the subsurface. At the present slow rate of flow, we expect the brine plume will exist for many years, and continued environmental damage at discharge points is anticipated.