Three-phase relative permeabilities of water-wet and oil-wet outcrops with two saturating histories (DDI and IID) are investigated by steady physical simulation experiments. CT Dual Energy Simultaneous Scanning (DESS) method was introduced to measure three-phase saturations accurately, which can eliminate the end effect. The relative permeability of each phase at a given saturation is calculated by Darcy law. The experiment results clearly show that for water-wet cores, the isoperms of water are straight lines, which means that the relative permeability of water depends on water saturation only. The isoperms of oil are curves concave towards 100% oil saturation point, and the isoperms of gas are curves convex towards 100% gas saturation point, which means that the relative permeabilities of oil and gas depend on all the three phase saturations. For oil-wet cores, all the isoperms of water, oil and gas are curves convex towards their 100% saturation points, which means that the relative permeabilities of water, oil and gas depend on all the three phase saturations. In addition, the isoperms of wetting phase are similar for the two saturation histories, while those of non-wetting phases are quite different. Though the isoperms are the same in shape, they are different in values and positions.
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