In order to realize the efficient development of lacustrine organic-rich shale oil reservoir in the lower sub-member of the third member of the Eocene Shahejie Formation and the upper sub-member of the fourth member of the Eocene Shahejie Formation in the Boxing Sag

Dongying depression

the geological data

such as thin sections

X-ray diffraction and the content of major and trace element

s are analyzed. After the data analysis

the types of lithofacies and the evolution stage of sedimentary paleoenvironment are determined

and eight lithofacies assemblages are also divided based on the relationship between lithofacies and sedimentary environments. Then

the favorable lithofacies for shale oil exploration and development are determined based on the comparison of geological and engineering “sweet spot” parameters of different lithofacies assemblages. The results indicate that: ① Six lithofacies types of organic-rich laminated argillaceous limestone and limestone mudstone

organic-rich layered argillaceous limestone and limestone mudstone

organic-poor massive argillaceous limestone and calcareous mudstone are mainly developed in the study area; ② The sedimentary paleoenvironment with the characteristics of paleoclimate from arid to humid

little change in paleoredox

paleosalinity from high to low

and paleo-provenance from less to more exhibited eight evolutionary stages

corresponding to eight lithofacies assemblage types; ③ Lithofacies assemblage D and F

with high shale oil productivity

are the favorable in the E

s

3L

and E

s

4U

respectively

and are in good agreement with the production practices. On the plane

the former is mainly distributed in the F159-F156-F160 well areas

and the latter is mainly distributed in FYP1-F116-F119 and F156-F159-F161 well area

which is a shale oil enrichment and high yield area in Boxing sag.