Abstract:

The Paleogene Shahejie and Dongying formations in the Bohai Sea area are rich in shale oil resources. However， limited explorations， as well as a lack of systematic investigation of the potential evaluation and endowment differences of shale oil resources， have constrained the exploration deployment and favorable play fairway selection in the area. Based on the actual exploration and exploitation conditions in the area， we ascertain the resource potential and favorable exploration targets of shale oil through the geochemical experiments， and whole-rock mineralogical analysis of source rocks. The results are as follows： （1） High-quality source rocks are widespread in the five hydrocarbon-rich sags in the Bohai Sea area. These source rocks exhibit moderate maturity， conducive to generating shale oil. The shale oil in the area can be classified into three types： scattered （ineffective） resources， low-efficiency resources， and enriched resources. The evaluation results show consistent enriched resources across various sags， predominantly with total organic carbon （TOC） content >1.8 % and pyrolysis hydrocarbon content （S₁） > 2.0 mg/g； （2） Shale oil-rich intervals are distributed across the five hydrocarbon-rich sags. Two shale oil-rich intervals with varying burial depths are found in the Huanghekou and Bozhong sags， with the interval in the Huanghekou Sag exhibiting smaller burial depth of around 2 800 m. In contrast， shale oil-rich intervals in the Liaozhong， Qikou， and Qinnan sags have burial depths ranging from 2 800～3 200 m； （3） For the 3^rd and 1^st members of the Shahejie Formation and the 3^rd member of the Dongying Formation in the Bohai Sea area， each of these members have shale oil play fairways covering an area exceeding 10 000 km². The five hydrocarbon-rich sags all boast shale oil resource potential beyond 15 × 10⁹ t， to which moderately to highly mature shale oil contributes more than 6.6 × 10⁹ t. Among these sags， the Huanghekou and Liaozhong sags， enjoying organic matter of high abundance and favorable types， shallow shale oil enrichment， and considerable resource potential， serve as the most favorable targets for current exploration.

Key words: resource potential, grading evaluation, oil-bearing capacity, shale oil, Shahejie Formation, Dongying Formation, Bohai Sea area