Banaszak, Konrad J.1
(1) Keramida Environmental, Inc, Indianapolis, IN
ABSTRACT: Geochemical Methods Beyond Cl/Br for Distinguishing Brines
In the past, great use has been made of the classic chloride to bromide ratio to
establish or disestablish connection between oil production waters and brine enriched
fresh waters. That ratio can be used to distiguish brines and to get to mixing ratios for
brines and fresher waters. On occasion, this tool is insufficient in that it may provide
equivocal answers or that reliance on a single thread of evidence may not be deemed
sufficient to scientifically support a conclusion. Cases may be lost in the arena of brine
influence on fresh water supplies, even when hydraulics and hydrogeology show the
connection of brine to fresh water most likely impossible! Consider the situations where
samples of the actual primary brine are not easily available or where ratios vary widely
in either of the "end member" waters.
To add to the tool kit of the interested professional, the isotopic composition of the waters and dissolved constituents in those waters can be utilized. Among the more powerful of these is the isotopic composition of the oxygen and the hydrogen of the waters themselves. Also, tritium may be used to get into conditions where other waters were added to brines for flooding projects. Chloride isotopes may be revealing. Finally, the isotopic composition of sulfur can be used.
AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.