Techniques and Problems in Sampling and Analyzing Formation Waters for Carboxylic Acids and Anions

Summary

Carboxylic acids and anions (CAA) have been known to exist in sedimentary formation waters since before the turn of the century. They have been proposed as essential agents in various geochemical processes such as metal ore migration and deposition, as precursors to natural gas, and as the mediators of organic-inorganic diagenesis. If the importance of CAA in geochemical processes is to be critically evaluated, viable samples of formation waters must be taken, and accurate and precise measurements of the CAA in the samples made. Key among sampling procedures designed to ensure sample viability are: flushing all production lines, sample lines, and sample containers with the formation fluid before the sample is taken; filtration of the sample through 0.1 μm at the time of sampling; addition of preservatives; and protection of the sample from light and elevated temperature. Accurate and precise measurements of the concentration of CAA in formation waters may be made by various analytical techniques, the most popular of which is ion chromatography. However, in complex mixtures this analysis is nontrivial; adjustments to the analytical technique may have to be made, and multiple runs performed on a single sample. Generally, a single sample run is an insufficient basis for meaningful interpretation.