Brine delineation and monitoring with electrical resistivity tomography and electromagnetic borehole logging at the Fort Knox well field near West Point, Kentucky

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Abstract

The potable water system at Fort Knox is threatened by brine contamination from improperly abandoned natural gas exploration wells. The Fort Knox well field is located near the town of West Point, Kentucky, in the flood plain of the Ohio River. At the site, unconsolidated sediments approximately 30 – 40 m thick, overlie shale and porous limestone. Brine is believed to flow vertically from the underlying formations to the unconsolidated aquifer through damaged or leaky well casings under a high hydraulic gradient from the artificially pressurized porous limestone, which is utilized for natural gas storage by a regional energy company. Upon reaching the unconsolidated aquifer, brinecontaminated groundwater enters water supply production wells under the pumping‐induced gradient. As part of the Fort Knox remediation strategy to reduce the impact of brine contamination, electrical resistivity tomography (ERT) and borehole electromagnetic (EM) logs are being collected annually to detect gross changes in subsurface conductivity. The 2009 ERT data show areas of high conductivity on the western (contaminated) side of the site with conductivities more than an order of magnitude higher than on the eastern (uncontaminated) side of the site. The areas of high conductivity are interpreted as brine contamination, consistent with known regions of brine contamination. Conductivities from the EM logs are consistent with the results from the ERT inversions. The EM logs show little change between 2008 and 2009, except for some small changes in the brine distribution in well PZ1. Yearly ERT surveys will be continued to detect new areas of brine contamination and monitor the remediation effort.

Additional publication details

Publication type Conference Paper
Publication Subtype Conference Paper
Title Brine delineation and monitoring with electrical resistivity tomography and electromagnetic borehole logging at the Fort Knox well field near West Point, Kentucky
DOI 10.4133/1.3445533
Year Published 2010
Language English
Publisher Society of Exploration Geophysicists
Contributing office(s) OGW Branch of Geophysics
Description 10 p.
Larger Work Type Book
Larger Work Subtype Conference publication
Larger Work Title Symposium on the Application of Geophysics to Engineering and Environmental Problems 2010
First page 913
Last page 922
Country United States
State Kentucky
City West Point