Smith, Bruce D.1, Joanna N. Thamke2, Jeffery G. Paine3
(1) U.S. Geological Survey, Lakewood, CO
(2) U.S. Geological Survey, Helena, MT
(3) Texas Bureau of Economic Geology, Austin, TX
Saline produced waters released during energy resource exploration and development can impact the quality of surface and sub-surface ground water. Estimation of the distribution and amount of affected ground water is an important consideration in understanding the nature of potential contamination and designing remediation programs. The first airborne helicopter electromagnetic over an oil field conducted in Mississippi in 1988 demonstrated that high cultural noise (power lines and pipelines) did not interfere with mapping areas of high subsurface conductivity. Some of these areas, near brine disposal pits that had been closed 20 years earlier, indicate plumes that had persisted even though the area receives more than 50 inches of rain a year. In 1991-1992 extensive ground electromagnetic surveys in the Williston Basin of Montana identified extensive areas of high conductivities not completely known previously. This survey also identified at least one source of contamination still contributing saline water to shallow aquifers. Ground and airborne geophysical surveys in an oil field near the central Red River in Texas was used to map extensive subsurface saline water. This study was the first to attempt to quantify the volume and mass of chloride contamination based on geophysical measurements. Sources of high electrical conductivities in addition to saline produced waters are clays, shales, and naturally saline water. Consequently in each of the above cases, detailed ground surveys and/or borehole geophysical logging identified the source of high electrical conductivities. Ground and airborne electrical and electromagnetic methods are effective non-intrusive means to map and characterize saline waters.
AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.