MULTISTAGE SUPERCRITICAL FLUID EXTRACTION OF PETROLEUM SOURCE ROCKS - APPLICATION TO SAMPLES FROM KIMMERIDGE CLAY AND POSIDONIA SHALE FORMATIONS

A study to determine whether supercritical fluid extraction can replace liquid extraction of source rocks has been initiated. The extractions have been performed with plain carbon dioxide, with small amounts of 2-propanol mixed with carbon dioxide and with carbon disulfide and tetrahydrofuran added to carbon dioxide to increase extraction yields. Multistage extractions were performed in order to obtain a compromise between rapid extraction and selective extraction. The extracts were collected either in a solvent or on a sorbent cartridge in a stream of water. The yields were similar to or higher than those obtained by liquid extraction. With a 3-stage extraction the first extract was dominated by saturates, the second by aromatics and the third by NSO-compounds. In preliminary results obtained with 1-2 g samples of Posidonia Shale, 0.8% soluble organic matter was extracted with multistage SFE and each stage was completed in 30 min. The extracts could be used for the determination of biomarkers.