Effects of fractal surface roughness and lithology on single and multiphase flow in a single fracture: An experimental investigation

This paper presents qualitative and quantitative analysis of single and multiphase flow in a single fracture based on experimental results and demonstrates relationships between the roughness and fluid movement and distribution. Experiments were conducted on seven perfectly-matching and tightly-closed rough model fractures reproduced from the single fractures of lithologically different seven rock blocks that were jointed artificially through laboratory indirect tensile tests. Transparent upper and opaque lower walls of these models facilitated the visualization of the flow experiments. Rough surfaces of the model fractures were first digitized. Then, using the gathered data in variogram analysis, surface roughness was quantified by fractal dimension. Another roughness quantification parameter was also handled as the ratio between total fracture surface area and planar surface area. Experimental measurements of flow were quantitatively correlated to surface roughness under different normal loading (aperture) conditions. Also, constant rate immiscible displacement experiments were performed to assess the roughness effect represented by seven different lithologies and wettability effect controlled by the material used in manufacturing the fracture samples on the residual saturation development.