Page 3 - Cilona_Tondi_2013
P. 3

Modelling  a  strike-slip  fault  system  affecting  porous  carbonates  in  Favignana  Island
               (Sicily, southern Italy)

                                                3
                         1,2
                                    2
                                                             1
               A. Cilona ; E. Tondi ; F. Agosta ; G. Johnson ; R. Shackleton 1

               1
                Midland Valley Exploration Ltd., Glasgow, United Kingdom.
               2
                Geology Division, School of Science and Technology, University of Camerino, Italy.
               3
                Department of Geological Sciences, University of Basilicata, Potenza, Italy

               Understanding  the  deformation  processes  in  carbonates  is  fundamental  for  geo-fluid
               exploitation.  Indeed,  in  these  rocks  fluid  containment  and  migration  are  influenced  by  fault
               zones and fractures.

               This  contribution  integrates  structural  analysis  and  numerical  modelling  approaches  aimed  at
               testing a new workflow for creating a 3D Discrete Fracture Network (DFN) model of a reservoir
               from outcrop data. In Favignana Island (Italy), several quarries provide 3D exposures of Lower-
               Pleistocene grainstones crosscut by a strike-slip fault system. This fault system is comprised of
               three types of structures: compactive shear bands (CSB); zones of bands (ZB); and, faults.

               The  DFN  model  was  built  using  the  Fracture  Modelling  module  within  the  Move  software
                                            ©
               package from Midland Valley . Analysis of an aerial photo was performed to identify the major
               faults. The intensity of CSBs and ZBs, was calculated from the lineament analysis tool of Move.
               We used the variation in intensity to build a DFN that reflects an intensity of deformation similar
               to the natural structural framework.

               Both CSBs and ZBs reduce permeability whilst slip surfaces enhance fault-parallel fluid flow.
               The DFN was then used to model the effect of deformation on the permeability of the host rock
               by  imposing  a  reduced  permeability  in  CSBs  and  ZBs  relative  to  the  host  rock  and  the  slip
               surfaces.

               This  semi-automated  process  of  lineament  analysis,  followed  by  the  use  of  power  law
               distributions to model sub-seismic scale features is proposed as a workflow for reservoir-scale
               assessment of the structural control on permeability in porous carbonate reservoirs.
   1   2   3