The 3rd member of the Shahejie Formation (Es³) in the Qibei Sub-sag, Huanghua Depression, Bohai Bay Basin holds enormous potential for shale oil exploration and exploitation. Using systematic experiments and analyses including core and thin section observations, scanning electron microscopy (SEM), X-ray diffraction (XRD), high-pressure mercury injection, total organic carbon (TOC) content analysis, and rock pyrolysis analysis, we explore the geological conditions and controlling factors for shale oil enrichment in the Es³⁽¹⁾. Six typical lithofacies of the Es³⁽¹⁾ are identified: laminated medium-grained calcareous-dolomitic shale, laminated fine-grained mixed shale, lamellar fine-grained mixed mudstone, lamellar medium-grained mixed mudstone, lamellar coarse-grained felsic mudstone, and massive medium-grained mixed mudstone. These mudstones/shales exhibit a TOC content ranging from 0.23 % to 2.57 %, with organic matter dominated by Types Ⅱ₁ to Type Ⅲ kerogen. The Es³⁽¹⁾ shales display peak pyrolysis temperatures (T_max) varying from 435 ℃ to 463 ℃, indicating that these shales are generally in the mature stage of thermal evolution. Major reservoir space types identified in the study area include intergranular pores, intercrystalline pores, inter-clay-flake pores, intragranular dissolution pores, organic pores, and microfractures. Shale oil predominantly occurs in inter-clay-flake and dissolution pores with small pore-throats, as well as intercrystalline pores and microfractures, both with large pore throats. Major factors controlling shale oil enrichment in the Es³⁽¹⁾ include TOC content, organic matter type, reservoir type, and sedimentary structures, which together form microscopic source rock-reservoir assemblages. Among the various lithofacies, the laminated medium-grained calcareous-dolomitic shale, laminated fine-grained mixed shale, and the lamellar fine-grained mixed mudstone exhibit effective source rock-reservoir assemblages, establishing themselves as favorable lithofacies for shale oil enrichment in the study area.