Occurrence states of the shale oil in the Shahejie Formation, Huanghekou Depression, Bohai Bay Basin, China

Abstract

To elucidate the distinct occurrence states of shale oil in the Paleogene Shahejie Formation within the Huanghekou Depression, a quantitative investigation was conducted employing multi-isothermal stage pyrolysis analysis technology. The results show that the free oil content and adsorbed oil content are the highest in the E2s3. With increasing maturity, the proportion of light and medium oils gradually increases, while the proportions of adsorbed and cracked oils progressively decline. The free oil content of shale oil is different in different sedimentary environments. The hydrocarbon generation range of the E3s1-2 is comparatively narrower than that of the E2s3, thereby resulting in a more extensive distribution of shale oil within the latter. The adsorbed oil content is influenced by the abundance of organic matter, while the free oil content is regulated by the abundance, type, and maturity of organic matter. The assessment of resource classification is carried out in the Shahejie Formation, establishing a theoretical basis for the subsequent investigation and exploitation of shale oil resources within the Shahejie Formation.