Utilizing small angle neutron scattering techniques on organic shales, this study presents an innovative approach for characterizing the status of oil occurrence, and new insights into pore scale assessment through scattering vector-pore size relationship. The results indicate the successful identification of different shale oil occurrence status, before and after solvent extraction of residual oil for four shale samples with different contents of total organic carbon. In addition, coupled with density distribution analyses, the work demonstrates that shale samples with lower total organic carbon contents typically signify a smaller radius of gyration with better oil mobility, which indicates a greater wave oscillation with a larger pore size to be estimated from the scattering vector. This work also elucidates the notable scenarios of an increasing pore size could correspond to a decreasing radius of gyration caused by mass density redistribution. For polydisperse systems, this research illustrates the variations in pore volumetric ratio impact the scattering intensity, whereas pore scale changes affect the oscillation pattern. This novel research of analyzing mass density distribution and pore scale information in real space is also suitable for other porous media systems.