Determining the lower limits of pore and throat sizes for shale oil occurrence is essential for reservoir evaluation, yet existing methods yield a single fixed threshold that fails to capture the heterogeneity of interbedded systems. This study addresses this limitation through integrated characterization of 59 core samples from the Chang 7 Member, Longdong area, Ordos Basin, using high-pressure mercury injection (HPMI), low-temperature nitrogen adsorption (LTNA), nuclear magnetic resonance (NMR), and field emission scanning electron microscopy (FE-SEM). Shale oil predominantly occurs in clay-free dissolution and intergranular pores, with minimal retention in clay intercrystalline pores. Residual oil content shows significant positive correlations with medium pore-throat volume and macropore volume, and negative correlations with fractal dimensions. Based on fractal analysis of pore-throat and pore size distributions, the lower limits for pore-throat sizes mainly vary from 24 to 60 nm (average 43 nm) and pore sizes from 65 to 198 nm (average 138 nm) across samples. These ranges directly reflect pore structure heterogeneity quantified by fractal characteristics, and cannot be reduced to a single threshold without losing critical reservoir information. 2D NMR T1-T2 spectra established for this formation indicate that free oil constitutes 53.4%–82.6% (average 68.4%) of residual oil, substantially exceeding adsorbed oil. Higher quartz and lower clay contents, combined with lower fractal dimensions and better-connected pore networks, correspond to elevated oil content and enhanced free oil enrichment. These results provide a heterogeneity-aware framework for sweet spot identification in continental interbedded shale oil systems.