The Effect of Authigenic Clays on Fault Zone Permeability

Clays are understood to form the majority of fluid-flow barriers in faulted reservoirs and numerous fault gouge seal studies have quantified volumes smeared abraded clays create along surfaces. However, clay-related permeability adjacent surface, including damage zone, has largely been neglected. Previous shown morphology distribution unfaulted authigenic clays, not just clay volume, exert a significant control on magnitude permeability. fault-related neither characterized deformed nor addressed their influence fluid-flow. In this study laboratory permeabilities faulted, bearing sandstones sampled from Otway basin (Australia) Orcadian (UK) present trends which; (a) do correspond expected patterns clay-bearing and, (b) cannot be explained using published models related changing volume. Microscopic analysis shows that faulting disaggregated similarly framework grain deformation, comminuted sheared grains. instead impeding fluid-flow, pore networks (using mercury injection porosimetry) showed increased connectivity, contributing development anisotropy. Contrary results impure sandstones, our show processes involving formation zone can increase reduce capillary threshold pressures rocks relative host rock.