Perpustakaan Digital ITB

The oil expulsion efficiency of shales is restricted by quite a few geological and geochemical factors, resulting in a great challenge to be evaluated quantitatively. In this paper, a semi-open pyrolysis simulation experiment based on a gold tube system was applied to simulate the oil generation and expulsion of seven lacustrine shale core samples with low maturities (Ro between 0.54% and 0.68%) and different kerogen types (types I and II) taken from the Shengli Oilfield, eastern China, and the corresponding seven suits of artificially matured sub-samples with a Ro range of 0.70–1.35% were obtained. The evolution of oil generation and oil expulsion, and their coupling relationships with oil retention for these samples with increasing maturity were investigated. The results show that the main stage of oil expulsion of these shales lags significantly behind the main stages of both oil generation and oil retention, with a corresponding Ro range of 0.80–0.90%, 0.70–0.85% and 0.65–0.82%, respectively. The oil expulsion efficiencies of these shales are not only constrained by their maturities, but also affected by their kerogen types and TOC contents. The shales with greater petroleum potentials and/or greater TOC contents have greater oil expulsion efficiencies. There is a good positive correlation between the retained oil and the total oil (i.e., the generated oil) for these shales as their Ro ? 0.98%, and this relationship is not significantly influenced by their kerogen types and maturities. The results may provide an alternative way for predicting the oil expulsion efficiency of natural shales according to their retained oil.