Tectonic Control on Cataclastic Strain Distribution and Permeability Reduction in Porous Sandstone Reservoirs

Abstract

We combine a thorough structural and petrophysical analysis of multiple deformation band sets (France, USA, Germany, Taiwan, Uk) with a broad dataset synthesis of deformation band permeability from the literature. Our analysis first reveals that strain localization in porous sandstones is characterized by fault zones surrounded by sets of shear bands showing a high degree of comminution. In contrast, distributed strain, does so in the form of pervasive and closely spaced compactional shear band and shear-enhanced compaction-band sets, showing moderate and low degree of comminution, respectively. Shear strain localization is inherent to the normal fault Andersonian regime and locations of upward-propagating underlying faults. In contrast, compactional strain distribution is inherent to thrust fault Andersonian regime. A synthesis of band permeability data reveals strong permeability decrease with the increase of comminution, especially in the normal fault regime. This demonstrates a major control of tectonic setting (extension/contraction) on fluid transmissibility of porous sandstones reservoirs containing cataclastic band networks. These results are consistent with a mechanical model proposed earlier based on the analysis of porous granular materials subjected to burial, different stress conditions and material properties.