The difference in phase continuity between spreading and nonspreading oils at low saturations was examined by measuring the oil phase effective diffusivity. Results indicated that for the sand and water saturations studied, the spreading oil(1-octanol) remained continuous at saturations as low as approximately 0.035 (the lowest oil saturation measured), while the nonspreading oil (n-dodecane) became discontinuous at a saturation of approximately 0.055. 1-Octanol also showed higher effectivediffusivities than the n-dodecane throughout the saturation range examined, indicating that the spreading oil was more highly connected. Two separate models, one for spreading and another for nonspreading oils, were used to describe the behavior of theoils in the unsaturated porous medium. Each model gave a reasonable prediction of the experimental data and was able to describe the difference in continuity between nonspreading and spreading oils.
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