Geochemistry of light petroleum from the North of Dongying Depression

Abstract

With ever-increasing exploration for oils, exploration has inevitably extended into deep layers. Considerable quantity of light oil is discovered from deep Es4 lower layer in the northern steep slope zone of Dongying Depression, Bohai Bay Basin. The oils are characterized by high content of saturated hydrocarbon and low concentration of biomarker and sulphur content. Eleven oil samples and forty-five source rock samples are finely analysed. According to the results of monomer hydrocarbon isotope analysis, carbon and oxygen isotope composition analysis and light hydrocarbon analysis, it is confirmed that the oils in deep strata of northern steep slope zone reach high mature lever. The light oils in the northern steep slope zone have a relationship with deep Es4 lower hydrocarbon source rocks by the results of monomer hydrocarbon isotope and light hydrocarbon analysis. Thermal evolution studies show the top Es4 lower hydrocarbon source rocks have a high thermal evolution level. The top Es4 lower hydrocarbon source rocks have relatively high organic abundance and are dominated by types I-II1 kerogen. This research is helpful for unravelling deep petroleum resources evaluation in this area. The viewpoint will be of great significance in future exploration. Moreover, the views in this paper can also be applied to other basins to explore for deep oil reservoirs.