Off-line-pyrolysis-gas chromatography-mass spectrometry analyses of drilling fluids and drill cuttings - Identification of potential environmental marker substances

Three different synthetic polymers commonly used in drilling fluids (carboxymethyl cellulose - CMC, hydroxyethyl cellulose - HEC and polyacrylamide - PAA) were analysed by off-line-pyrolysis-gas chromatography-mass spectrometry (off-line-Py-GC-MS). The aim of this study was to determine specific environmental marker compounds for the identification of contamination due to drilling activities. In a first step, reference materials of the main constituents of commonly applied water-based drilling fluids were purchased and analysed to identify potential indicator substances. For each polymer a set of two to three specific pyrolysis products was determined. Afterwards, four CMC, one HEC and two PAA based drilling fluids were pyrolysed in order to retrieve the previously identified compounds in drilling fluid mixtures. All indicator compounds were identified. In a third step, spiking experiments on drill cutting samples of various depths of one well proved the traceability of the applied polymers and verified the applicability of the indicator systems in terms of sensitivity and specificity.