关键词: 鄂尔多斯盆地, 长71-2亚段, 源储组合, 储层特征, 页岩油, 富集模式

Abstract: The pronounced heterogeneity of source–reservoir architectures in continental shale systems has not yet been adequately captured by existing classification schemes, which constrains a systematic understanding of shale oil enrichment mechanisms. Although various source–reservoir classification frameworks have been proposed, their applicability to the strongly heterogeneous continental shales of China remains limited, and consequently the controlling role of source–reservoir relationships on shale oil enrichment has not been comprehensively elucidated. This paper takes the interbedded shale oil reservoirs of the Chang 71-2 Submember in Longdong area of the Ordos basin as the research object. Based on the superimposition relationship and thickness of sandstone and mudstone, combined with X-ray diffraction tests, three types of source-reservoir assemblages are classified. Furthermore, relying on high-pressure mercury intrusion tests, nitrogen adsorption tests, ordinary thin sections, casting thin sections, scanning electron microscopy images, and two-dimensional NMR T1-T2 spectra, the differences in shale oil reservoirs, pore structures, and occurrence states are comprehensively explored. The results show that: type Ⅰ source-reservoir assemblage is dominated by mesopores and macropores, with a small amount of micropores, featuring good pore connectivity and uniform pore distribution; It is mainly composed of intergranular pores, with a small number of intragranular dissolution pores developed, and microfractures are well-developed; Movable oil is widely distributed in mesopores and macropores, making it a favorable assemblage for shale oil enrichment. Type Ⅱ source-reservoir assemblage has relatively developed micropores and mesopores; It develops a small number of intergranular pores, a small number of intragranular dissolution pores, and a small number of microfractures; Heavy-component residual oil is widely distributed in micropores, with moderate mobility, resulting in moderate shale oil enrichment capacity. Type Ⅲ source-reservoir assemblage is dominated by micropores; It is mainly composed of clay mineral cementation pores and carbonate cementation pores, with dense pores and poor pore connectivity; Capillary-bound water is widely distributed in the pores, restricting the flow of movable oil and being unfavorable for shale oil enrichment. Felsic minerals significantly promote the occurrence and migration of movable oil in mesopores and macropores, whereas clay minerals favor the retention of oil in adsorbed or residual states; Together, these mineralogical components constitute the primary controlling factors for shale oil enrichment. In contrast, average pore radius, maximum mercury saturation, porosity, permeability, and specific surface area act as secondary controlling factors for shale oil enrichment.