Experiments using transparent porous media, where the indices of refraction of the solid grains and the wetting fluid are matched, can be used to quantify fluid saturations from digital images. In this study, significantly more efficient calibration and validation methods for unsaturated transparent porous media were developed, which used just three images and one saturation measurement. Imbibition and drainage column experiments were used to define the pixel intensity and saturation at residual wetting fluid saturation, as well as at residual nonwetting fluid saturation in two gradations of transparent porous media used for validation. The other images were pixel intensity at 100 and 0% wetting fluid saturation. Results from the drainage and imbibition experiments on the two transparent porous media gradations showed a log-linear saturation–pixel intensity relationship, which agreed with the validation points from this study as well as those using a previous calibration method. We expect that this new calibration procedure will allow efficient development of saturation–pixel intensity relationships for the investigation of multiphase flow using transparent porous media under a variety of conditions.

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