关键词: 古近系, 阜宁组二段, 页岩油, 勘探突破, 高邮凹陷

Abstract: In 2022, two key shale oil wells (Well HY1HF and Well H2CHF) were explored for Member 2 of Paleogene Funing Formation in Gaoyou sag of Subei Basin, and an industrial oil flow of 29.7 t/d and 50.5 t/d was separately obtained after fracturing in the drainage and production stage, achieving a great breakthrough in the shale oil exploration for Member 2 of Funing Formation in Gaoyou sag. Based on the observations of cores and thin sections from wells such as Well HY1, whole rock mineral composition analysis by X-ray diffraction, nitrogen adsorption analysis, nuclear magnetic resonance analysis, and organic geochemical analysis of frozen cores, in combination with the dynamic production data of Well HY1HF and Well H2CHF, the paper systematically analyzes the geological characteristics of Member 2 of Funing Formation in Gaoyou sag, and further reveals the enrichment regularities and controlling factors of shale oil from Member 2 of Funing Formation in Subei Basin. Semi-deep to deep lacustrine subfacies shale are developed in Member 2 of Funing Formation of Gaoyou sag, characterized by large thickness and wide distribution, laying the foundation for the enrichment of shale oil. Shale lithofacies control the horizontal and longitudinal distribution of "source sweet spots" and "reservoir sweet spots", among which the lithofacies with relatively high content of clay minerals correspond to good hydrocarbon generation potential, and those with high content of felsic minerals and carbonate minerals have good physical properties and pore-throat structure. According to the characteristics of lithologic association, the shale oil reservoir in Member 2 of Funing Formation can be divided into three types, i.e., self-generating and self-preserving shale oil (Type Ⅰ), mud generating and carbonate preserving shale oil (Type Ⅱ), and mud generating and silty laminae preserving shale oil (Type Ⅲ). High-quality pore-fracture system is developed in the source-reservoir combination of Type Ⅱ shale oil, characterized by good oil content and high mobility. Moreover, the existing dynamic production data indicate that Type Ⅱ shale oil reservoir has good productivity. In addition, good preservation conditions and pressurization resulted from secondary hydrocarbon generation are the key to high and stable production of shale oil. The shale oil exploration breakthrough in Member 2 of Funing Formation of Gaoyou sag indicates that the Paleogene shale oil in Subei Basin has good exploration prospects and Gaoyou sag is a key area for increasing reserves and production. These research results have important reference and guiding significance for the exploration and exploitation of shale oil in continental faulted basins in eastern China.

Key words: Paleogene, Member 2 of Funing Formation, shale oil, exploration breakthrough, Gaoyou sag