Characteristics and facies classification of oil shales in major continental basins of China

The continental oil shales of China exhibit pronounced heterogeneity in organic matter abundance, mineral composition, and sedimentary structures. Characterizing their lithofacies is therefore fundamental for reconstructing depositional environments, assessing resource potential, and guiding resource development. In this study, oil shale data from major continental basins, including the Songliao, Ordos, and Junggar basins, were compiled, with a focus on TOC, XRD-derived mineralogical compositions, and sedimentary structural information. Based on an integrated evaluation of organic geochemical and sedimentological parameters, TOC, bedding characteristics, and mineralogy were selected as key criteria for lithofacies classification. Accordingly, continental oil shales in China were subdivided into 24 lithofacies types, such as organic-rich laminated argillaceous mudstone (RLAM) and organic-poor massive siliceous mudstone (PMSM). Among them, organic-rich laminated mixed mudstone (RLMM), organic-rich laminated siliceous mudstone (RLSM), and organic-rich laminated calcareous mudstone (RLCM) are identified as the most prospective lithofacies due to their relatively high TOC contents, favorable mineralogical brittleness, and well-developed lamination, which collectively indicate superior hydrocarbon generation potential and reservoir quality.