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Paper No. 6
Presentation Time: 9:45 AM


PANNO, Samuel V.1, KELLY, Walton R.2, HACKLEY, Keith C.1, ASKARI-KHORASGANI, Zohreh1, RICE, Richard J.1, HWANG, Hue-Hwa1 and KROTHE, Noel C.3, (1)Illinois State Geological Survey, University of Illinois, 615 E. Peabody Drive, NA, Champaign, IL 61820, (2)Illinois State Water Survey, University of Illinois, 2204 Griffith Drive, NA, Champaign, 61820, (3)Hydrogeology Inc, 1211 South Walnut Street, Bloomington, IN 47404,

The successful sequestration of CO2 into deep geologic formations is contingent upon the absence of natural pathways to the surface. The Illinois Basin is the location of five US Department of Energy test sites involving the injection of liquid CO2 into geologic formations. Predicting the movement of CO2 in the vicinity of the injection point and the potential for its escape to shallow groundwater and/or the surface is critical to long-term containment.

Groundwater quality in the Illinois Basin, like most intracratonic basins in the Midwestern US, transitions from extremely fresh near surface (Cl = 1 to 13 mg/) to concentrated brines at depth (Cl > 100,000 mg/L). Naturally-occurring saline anomalies have been identified throughout the Illinois Basin (in Illinois, southern Indiana and northern Kentucky) as springs or localized saline seeps into fresh shallow drift aquifers, and many are of historic significance. In the course of this investigation, about 30 locations of upwelling saline groundwater within the Illinois Basin have been identified, and are currently being investigated. All saline springs are being sampled for chemical and isotopic composition with emphasis on halide chemistry (Cl, Br, I) in order to determine the source formations of the salinity. In addition, six cross sections through the Illinois Basin are being prepared and will include all available Cl concentrations to help evaluate local and regional groundwater movement.

The saline springs of the Illinois Basin were found to be coincident with geologic structures within, and at the margins of the Illinois Basin. Preliminary results reveal that Cl/Br ratios range from 150 to 700 and originate from Cambrian- to Pennsylvanian-age sedimentary rocks. Chloride concentrations of these springs are typically around 500 mg/L and rarely exceed 8000 mg/L. Springs with the greatest concentrations of Cl also contain H2S which supports colonies of white, filamentous, chemolithotrophic sulfide-oxidizing bacteria.

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