@article{YOU2025, 
author = {Zuhui YOU and Jianhua ZHAO and Xiugang PU and Keyu LIU and Wei ZHANG and Zhihao WANG and Zhannan SHI and Wenzhong HAN and Quansheng GUAN and Jiyang WANG},
title = {Controlling factors in oil-bearing properties and shale oil enrichment patterns of the 1st sub-member of the 3rd member of the Paleogene Shahejie Formation, Qibei Sub-sag, Huanghua Depression, Bohai Bay Basin},
year = {2025},
journal = {Oil & Gas Geology},
volume = {46},
number = {2},
pages = {443-461},
keywords = {lithofacies type, microscopic source rock-reservoir assemblage, shale oil, 1st sub-member of the 3rd member of the Shahejie Formation (Es3(1)), Qibei Sub-sag, Bohai Bay Basin},
url = {https://www.sciopen.com/article/10.11743/ogg20250208},
doi = {10.11743/ogg20250208},
abstract = {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 (Tmax) 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.}
}