Slice experiment of oil-bearing core rock and its implications

The contamination of rocks during drilling, sampling, storage or handling processes will affect the organic geochemical information of biomarkers, and will even lead to the wrong interpretations of the origin and evolution of early life on the earth especially for preCambrian sediments. A slice experiment was employed on the oil-bearing argillaceous dolomite from the Hongshuizhuang Formation in order to discuss the influence of contamination on biomarkers. The aliphatic biomarkers showed a big difference between outside oil show (OOS) and inside oil show (IOS), whereas the difference for the aromatic biomarkers was small. Most of the biomarker ratios showed a considerable discrepancy between OOS and IOS except a few parameters. Steranes were not detected in the IOS, indicating that the existence of steranes remained for further validation. It was recommended that cutting the surface of core samples before organic geochemical experiments could avoid contamination.