Oil Content and Mobility of Xiaganchaigou Formation in Yingxiongling Area, Qaidam Basin: Dominant Lithofacies and Controlling Factors

ABSTRACT Mixed shale represents an important target for shale‐oil exploration in lacustrine basins. However, its strong heterogeneity leads to pronounced variations in shale‐oil content and mobility. Therefore, identifying favorable lithofacies and clarifying their controlling factors are critical for shale‐oil sweet spot exploration. In this study, lithofacies of the Xiaganchaigou Formation in the Yingxiongling area, Qaidam Basin, were classified on the basis of mineral composition and subsequently evaluated using geochemical, pore structure, brittleness, and fracability characteristics. Mixed shale is volumetrically dominant, whereas calcareous shale exhibits more favorable oil content and mobility and is identified as the most favorable lithofacies within the studied interval. The controlling factors of shale‐oil content differ from those of mobility among different lithofacies. Shale‐oil content is mainly controlled by shale thickness, organic matter abundance, and thermal maturity, whereas mobility is primarily influenced by fracability, mineral composition, and pore structure. Favorable lithofacies are, therefore, characterized by the coupled effects of organic matter abundance, mineral composition, pore structure, and fracability. These findings provide a basis for shale‐oil sweet spot evaluation and target optimization in the Xiaganchaigou Formation of the Yingxiongling area.