Abstract: The characteristics,controlling factors and oil-bearing capability of the Lucaogou reservoir in Jimusaer sag were studied based on core observation,thin section features,as well as data from scanning electron microscopy (SEM),physical and geochemical analysis.The results indicate that the sedimentary environment of the Lucaogou Formation is of saline lacustrine,in which a set of fine-grained hybrid sedimentation of lacustrine dark mudstone,silty-fine sand and carbonate was developed.Its lithology is mainly diamictite characterized by alternating thin beds of silty-fine sand,clay and carbonate.Reservoir space is dominated by intergranular dissolved pores and intercrystalline micro-pores,with residual intergranular pores ranked second and followed by a few cracks.The controlling factors for the reservoir properties of Lucaogou shale include sedimentary facies,lithology,organic carbon content (TOC) and diagenesis.The reservoir properties of the Lucaogou shale in the study area show a remarkable control on oil-bearing capability,and the oil film was well developed in dolomitic rocks.Reservoir wettability is primarily neutral,followed by localized lipophobicity.In addition,the reservoir micro-wettability change from oil-wet and oil-bearing to hydrophilic and moisture-containing with smaller pore sizes,as showcased by the field emission scanning electron microscopy.It demonstrates that the shale oil reservoir in the Lucaogou Formation,Jimusaer sag,is capable of high saturation oil-bearing,which has laid a sound foundation for the shale oil exploration and development in the region.

Key words: oil-bearing property, wettability, reservoir space, reservoir, shale oil, saline lacustrine basin, Lucaogou Formation, Jimusaer sag, Junggar Basin