Trapping zones : The effect of fracture roughness on the directional 3 anisotropy of fluid flow and colloid transport in a single fracture

8 [1] In this paper we quantify the influence of geometry and 9 distribution of surface roughness to the directional 10 anisotropy of fluid flow and transport properties of a 11 single fracture. Roughness of fractures appears to have first 12 order control on how they behave mechanically and 13 hydraulically. We directly quantified the surface roughness 14 of a single fracture using high-resolution laser scanning 15 confocal microscopy. This roughness was input into directly 16 coupled numerical models of fluid flow and transport. We 17 simulated the transport of colloids (microspheres) through 18 the fracture. We found tailing in the breakthrough and 19 sensitivity of the breakthrough to flow direction in the 20 fracture. Microspheres were observed to be trapped in 21 low velocity zones on the lee side of fracture walls. This 22 was not observed in smooth or sinusoidal varying fracture 23 wall geometries. These observations have significant 24 implications for quantifying the transport of dissolved and 25 solid phase materials (colloids) through fractured rock. 26 Citation: Boutt, D. F., G. Grasselli, J. T. Fredrich, B. K. Cook, 27 and J. R. Williams (2006), Trapping zones: The effect of fracture 28 roughness on the directional anisotropy of fluid flow and colloid 29 transport in a single fracture, Geophys. Res. Lett., 33, LXXXXX, 30 doi:10.1029/2006GL027275.