Page 14 - Tondietall2015

Italian Journal of Geosciences Accepted manuscript

Since the data on displacements of the studied faults are available, we plotted these data versus
fault core permeability measurements aimed at examine the possible relationship between the fault
permeability and the fault slip (see for example JOURDE et alii, 2002). However, figure 10 clearly
displays no correlations exist between fault core permeability and fault displacement for the faults
affecting the two carbonate grainstones. This could be related to the deformation mechanisms for
fault nucleation in porous carbonates (TONDI et alii, 2006; TONDI, 2007). In fact, porosity reduction
due to compaction and pressure solutions that cause the permeability reduction in the fault core, is
documented also at the initial stage of fault formation in porous carbonates (TONDI, 2007);
increasing slip may determine a large thickness of fault core (TONDI et alii, 2012) but doesn’t
change its petrophysical properties.

The results of this study reveal that faulting may have a remarkable effect on the permeability
of porous carbonate grainstones. Thus, we suggest that fluid circulation paths could be dependent
on orientation, density and connectivity of these fault zones. Moreover, by comparing two
grainstones with significant differences in both effective porosity and pore dimensions, we
highlighted the effects of both parameters on the overall permeability of faulted porous carbonate
reservoirs/aquifers.

CONCLUSIONS
In this contribution we present the results of a study aimed at assessing the relationships
between deformation processes taking place within fault zones and their impact on the overall rock
permeability of porous carbonate media. The study takes advantage of in situ air permeability
measurements carried out across sub-seismic resolution fault zones crosscutting high-porosity
carbonate grainstones of Cretaceous and Pleistocene ages. The former are exposed along the north-
eastern flank of the Majella Mountain (Abruzzo, Italy), the latter on the eastern edge of the
Favignana Island (Sicily, Italy). Fault zones, which represent the late evolutionary stage of former