Environmental Health - Toxic Substances
Environmental impacts of petroleum production: 1- The fate of inorganic and organic chemicals in produced water from the Osage-Skiatook Petroleum Environmental Research B site, Osage County, OK
Yousif K. Kharaka
Presented at the 9th International Petroleum Environmental
Full Text of the Paper (pdf file 1.54 MB)
About 15 scientists from the U. S. Geological Survey, other Federal agencies and academia 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 and ground water and the local ecosystem at the Osage-Skiatook Petroleum Environmental Research (OSPER) A and B sites, located in Osage County, OK. The Branstetter lease, OSPER B site, is typical of many aging petroleum fields in Osage County, which ranks among the top oil and gas producing counties in Oklahoma with close to 40,000 wells. Current production in Osage County is mainly from stripper wells (averaging ~2.8 bbls/d oil and >30 bbls/d brine) that are shallow, mostly 300-700 m in depth, and produce from several sandstones of Pennsylvanian age. About one hectare of land at the OSPER B site is affected by salt scarring, soil salinization and brine and petroleum contamination due to the leakage of produced water and associated hydrocarbons from two brine pits and due to accidental releases from active tank batteries. Eventually, the bulk of inorganic salts and some dissolved organic species in the released brine reach, directly or via the two local streams, the adjacent Skiatook Lake, a 4250-hectare reservoir that provides drinking water to the local communities and is a major recreational fishery.
About 40 water samples were obtained from several oil wells
at the B site and adjoining areas, the two brine pits, several brine pools
and seeps in the impacted area, local streams, Skiatook Lake, and from
about 20 boreholes (1-71 m deep), recently drilled and completed with
slotted PVC tubing. Water level monitoring and additional sampling is
continuing. Results to date show that the produced water is a high-salinity
(~150,000 mg/L total dissolved solids) Na-Ca-Cl brine, with relatively
high concentrations of Sr, Mg and NH4, but low amounts of SO4 and H2S.
With the exception of Fe and Mn, the concentrations of trace metals are
low, and the values of dissolved organics are relatively low. As the brine
flows from the brine pits through the shallow eolian sand, colluvial and
alluvial deposits to the streams and Skiatook Lake, it is diluted by infiltrating
water from precipitation. Its chemical composition is modified by sorption,
mineral precipitation/dissolution, transpiration, volatilization and oxidation/reduction
reactions. Bacteria likely play an important role in many of these reactions.