More than 100 water samples have been obtained from OSPER "B" site; from the two brine pits, several brine pools and seeps, local streams, Skiatook Lake, and from 40 boreholes (1-71 m deep), recently drilled and completed. Results show diluted brine (up to ~25,000 mg/L TDS) and minor amounts of oil flow from the brine pits through the shallow eolian sand, colluvial and alluvial deposits towards the Skiatook Lake, a 4250-hectare reservoir that provides drinking water to the local communities and is used as a recreational fishery. Preliminary results from four relatively deep wells completed in May 2004 clearly show that produced-water brine and minor oil have penetrated the thick (3.5-6 m) shale unit and contaminated the underlying aquifers. The chemical composition of released brine is modified by sorption, mineral precipitation/dissolution, transpiration, volatilization and bacterially mediated oxidation/reduction reactions, in addition to mixing with percolating precipitation water, lake water and pristine groundwater.