Fault Permeability in Porous Sandstone Reservoirs: a Short Review of Controlling Factors

Summary In poorly lithified and porous sandstone reservoirs, the typical fault zone structure consists of a narrow fault core (made of foliated cataclasites and gouges) surrounded by a damage zone (containing tabular deformation bands). Both fault core and damage zone are generally low permeable domains, but with permeability values that varies over a large range from 10-6 to 10 Darcy. Depending on their internal architecture (e.g., fault core and damage zone widths, density of deformation bands) and related petrophysical properties, faults in porous sandstones can either act as retarders, effective seals or even conduit-barrier for fluid flow. Several geometric, environmental and lithological factors control the structure, petrophysical properties and, consequently, the hydraulic behaviour of faults developed in porous rocks. The aims of this contribution are (i) review the published papers on faulted poorly lithified sandstones to extract fault permeability data, (ii) integrate published dataset with unpublished material to increase the number of case studies, and (iii) compare the datasets to understand the fault permeability evolution in different types of sandstones. The ultimate target of this contribution is to stimulate the discussion on the main factors (particularly fault displacement, burial depth and host rock mineralogy) controlling the evolution of fault zone permeability.