Abstract: To clarify the main controlling factors of interlayer oil enrichment, this study classifies hydrocarbon supply modes based on the spatial relationships between source rocks and reservoirs, including their relative development positions and vertical/lateral configurations. The oil-bearing properties under different hydrocarbon supply modes were characterized using indicators such as the proportion of oil-bearing wells, hydrocarbon charging thickness, charging intensity, and oil saturation, thereby revealing the differential enrichment characteristics of interlayer oil. The results show as follows. In the Jiyuan area of the Ordos basin, four types of hydrocarbon supply modes were identified: Vertical dual-source supply type, bottom source type, lower source type, and lateral source type. Among them, the vertical dual-source supply type and lateral source type exhibit superior oil-bearing properties, while the bottom source type and lower source type are comparatively less enriched. The oil content of the vertical dual-source supply types is primarily governed by the reservoir's storage capacity, whereas that of the bottom supply type is controlled by the interplay between dynamic forces and resistance. The oil content of the lateral source type depends on the connectivity of the sand bodies connecting the source rock, while the oil content of the lower supply type is significantly influenced by the fracture density of overlying sandstones.

Key words: hydrocarbon supply mode, interlayer oil, source rock, reservoir, enrichment mechanism, Member 7 of Yanchang Formation, Ordos basin