Page 4 - Tondietall2015

Italian Journal of Geosciences Accepted manuscript

for faults in tight carbonates (e.g., AGOSTA, 2008), no studies have been so far focused on the
relationships between deformation and fault permeability in porous carbonate grainstones.

In this contribution we present the results of in situ air-permeability measurements carried out
across normal to strike-slip, sub-seismic resolution fault zones developed in high-porosity carbonate
grainstones of Cretaceous (Majella Mountain, Abruzzo), and Pleistocene (Favignana Island, Sicily)
ages (fig. 1). With the general objective to assess the control exerted by sub-seismic resolution
faults on the overall permeability of porous carbonate reservoirs/aquifers, this work is aimed at
establishing meaningful relationships between deformation processes (taking place within fault
damage zones and fault cores) and fault rock permeability.

METHODOLOGY
A total of 194 in situ air-permeability measurements was carried out across nine selected fault
zones. Permeability measurements were performed in undeformed and faulted grainstones by a
TinyPerm II Portable Air Permeameter manufactured by New England Research (NER). This has a
5 mm nozzle and provides reliable permeability values from 10-4–101 Darcy (ROTEVATN et alii,
2008) further extended for high-porosity materials in NER laboratory up to ~5x103 Darcy
(BALSAMO et alii, 2013). Measurement sites in the field were scraped with a putty knife to remove
weathering effects and gently brushed to remove dust. A silicon tip formed a seal to prevent air
leakage from the mini-permeameter nozzle. Data in the undeformed porous grainstones were
acquired both in vertical and horizontal sections by multiple measurements in each site of the
transect. Fault core and damage zone permeability measurements were acquired also in vertical and
horizontal sections by multiple spots oriented parallel to the fault strike.
Helium pycnometer analysis was performed on seven undeformed cores (Diameter =19 mm;
Height = 5.1 mm), two from Favignana grainstones and five from Majella ones, respectively. Pore
throat distribution for the two grainstones was established starting from a mapped photomicrograph
following the methodology explained by CILONA et alii (2012).