Shale Oil Mobility Based on Microscopic Wetting Properties of Mineral Components

As an important unconventional energy resource, the efficient development of shale oil is of great significance for ensuring energy security. Shale reservoirs exhibit characteristics of low porosity and permeability, complex pore structures, and diverse mineral compositions, resulting in extremely complex wettability characteristics. Wettability, as a key parameter controlling oil phase occurrence and flow, directly affects shale oil development efficiency. Traditional wettability studies mainly rely on macroscopic contact angle measurements, which struggle to accurately reveal wetting behavior in nanoscale pores and its control mechanisms on oil phase mobility. This study aims to establish a multi-scale wettability characterization method for shale reservoirs and reveal the intrinsic relationships among wettability characteristics, pore structure, and oil phase mobility. Based on Gulong shale samples, macro- and microscopic contact angle measurements were employed to characterize multi-scale wettability features, nuclear magnetic resonance technology was used to independently evaluate oil phase mobility in different-scale pores, and systematic correlation analysis was conducted to explore the control mechanisms of wettability on mobility. The study found that although microscopic contact angles are systematically larger than macroscopic values, the measurement trends from both methods are highly consistent, validating the reliability of cross-scale characterization. Different from previous single-scale understanding, this study reveals that pore structure and mobility require synergistic evaluation: optimal reservoirs may not be those with the highest proportion of large pores, but rather those with balanced pore structure (60%-80% large pore proportion) and high mobility in all pore sizes; additionally, mineral components exhibit differentiated control effects on multi-scale pore system recovery rates, with quartz content showing significant positive correlation with both large and small pore recovery rates, while different clay minerals demonstrate scale-dependent complex influences. Through correlation analysis, qualitative relationships between wettability and mobility, as well as quantitative evaluation models between mineral components and mobility, were established. This research provides new evaluation methods for shale oil reservoir sweet spot identification, emphasizing the need to comprehensively consider the synergistic effects of pore structure, wettability, and mobility.