Continuous In-Situ Measurements of Nitrates and Other Contaminants Utilizing Specialized Geophysical Logging Devices

NEWMAN, JOSEPH L., and GARY W. CORBELL, Welenco, Inc., Bakersfield, CA

The presence, nature, and extent of aquifer contamination by nitrates and other inorganic chemicals is of great concern in major portions of the United States. Existing geophysical logging and sampling methods are all very helpful in delineating aquifer contamination; however, it is essential that the contaminant be measured directly at the face of the aquifer to fully understand the extent of the inorganic contamination. As a result, a unique method has been developed which will detect nitrates and other inorganic chemicals in-situ as a continuous measurement of contamination vs. vertical depth.

In particular, this paper is a case history study of the use and results of Nitrate and Fluoride Logging Probes. Using time-proven laboratory methods for measuring specific ions and incorporating unique methods and procedures, downhole analysis is now available. This analysis offers invaluable assistance in detecting nitrate and fluoride contamination in existing wells and defines zones to be bypassed when replacement wells are drilled.

We present numerous graphs, pictures, and actual field logs of contaminated aquifers. Because this is an entirely new logging method, additional logging devices are used concurrently with the ion selective probes to provide for a more thorough interpretation of the results. We give several recommendations to ensure that future uses of this methodology are appropriate and reliable with emphasis on procedures and interpretation. Finally, we present the advantages and disadvantages of this methodology.

AAPG Search and Discovery Article #91009©1991 AAPG-SEPM-SEG-SPWLA Pacific Section Annual Meeting, Bakersfield, California, March 6-8, 1991 (2009)