IDENTIFICATION OF AQUIFER CONTAMINATION BY OIL-FIELD BRINES USED FOR DUST ABATEMENT

Oil-field brines were spread during several recent years for dust abatement over an industrial supplies storage yard near Wooster in northern Ohio. The site is located on a thin ground moraine covering bedrock of Pennsylvanian age sandstone ridge. The sandstone serves as a local phreatic aquifer, cropping out in nearby creek that acts as line of discharge for the aquifer. Elevated salinity has been reported in a number of water wells located between the industrial supplies storage yard and the creek. The objective of our investigations and data analysis was to either prove or disprove the hypothesis that water in the wells have had been contaminated by oil-field brines. In our investigations we concentrated on analysis of the local hydrogeology, as represented in the well-logs of the involved water wells and on the chemical composition of water samples taken at various times from the water wells. Also, the chemical compositions of the water samples were compared with two chemical analyses of oil-field brines that were apparently used in spreading on the ground in the vicinity of the water wells to reduce the dust on unpaved ground surfaces, as well as with chemical analyses of large number of oil-field brines from the four oil/gas bearing formations in Ohio: Clinton, Newburg, Oriskany and Berea. Aside of the commonly used for identification of contamination by oil-field brines ionic ratios, e.g. [Na]/[Cl], [Ca]/[Cl], [K]/[Cl], [Ca]/[SO4], [Ca]/[Mg] and [Sr]/[Cl] we found particularly useful the complex ratios of {[Ca]/([Ca]+[SO4])}/{[Na]/([Na]+[Cl])} proposed by Hounslow (1995).