Effect of surface roughness and lithology on the water-gas and water-oil relative permeability ratios of oil-wet single fractures

摘要

This paper discusses the effect of surface roughness on the water-gas and water-oil relative permeabilities of single fractures. After manufacturing 20 x 20 cm transparent replicas of fractures developed under tensional load, constant injection rate displacement experiments were performed. Saturation distribution against time was visually monitored and the residual phases were determined for seven fracture samples of different rock types. These values were then correlated to the fractal and statistical properties of the fracture surfaces. Fractures developed from less porous and larger grain size rock samples (marbles) showed "larger scale" heterogeneity, which caused residual phase saturation in the form of large pockets. Porous rocks with small grain sizes (limestones) showed "small scale" heterogeneity yielding residual saturations in small pockets. The fractal dimension obtained by the triangular prism method has more control on the residual saturation distribution than the other fractal and statistical parameters.