SELECTIVITY AND YIELDS IN SUPERCRITICAL-FLUID EXTRACTION OF TAR-MATS AND SOURCE ROCKS

Extraction of tar-mats and a petroleum source rock with supercritical carbon dioxide has been performed in an attempt to obtain class fractionation by multistage extractions. Depending on the experimental conditions the total yields were similar to or higher than the yields obtained with solvent extraction. The tar-mats were extracted with a 3-stage procedure and the bulk of the hydrocarbon biomarkers was found in the second fraction. The source rock was extracted first with a 5-stage, then with a 2-stage process. The 2-stage extraction contained the biomarkers in the first fraction, and the process was more rapid than the 5-stage extraction, although the yields were slightly reduced. Collection on C-18 sorbent cartridges was performed both with and without water flow and compared to collection in a solvent. Cartridge collectors equipped with a small vacuum at the outlet were easy to use, free for solvent vapors, but resulted in loss of the volatile end of the extract.