Identification and controlling factors of multi-scale lithofacies for continental shale under an isochronous stratigraphic framework: a case study in Dongying Sag, Bohai Bay Basin

At present, due to the diversity and complexity of terrestrial shales, it is difficult to identify and predict the shale facies precisely. At the same time, the controlling factors for shale development are not well understood. The study of shale facies and controlling factors in the Dongying Sag has allowed the identification of features of multi-scale lithofacies in lacustrine shale of different grades, and further identified two controlling factors. Lithofacies can be divided into layer coupling, layer coupling group, lithofacies domain and lithofacies sequence. The layer coupling is controlled jointly by paleoproductivity, monsoon and oxidation-reduction, while the layer coupling group-lithofacies domain-lithofacies sequence are controlled jointly by material source, climate and structure, thus resulting in the complexity and diversity of continental shale lithofacies. The results can be used to systematically understand the multi-scale characterization and research of lacustrine shale lithofacies.