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Marine and Petroleum Geology xxx (2013) 1e16

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Marine and Petroleum Geology

journal homepage: www.elsevier.com/locate/marpetgeo

Fluid flow numerical experiments of faulted porous carbonates,
Northwest Sicily (Italy)

b
c
c
Marco Antonellini a, * , Antonino Cilona , Emanuele Tondi , Miller Zambrano ,
Fabrizio Agosta d
a
Department of Biological, Geological and Environmental Sciences, University of Bologna e CIRSA, via San Alberto 163, 48123 Ravenna, RA, Italy
b
Department of Geological and Environmental Sciences, Stanford University, CA, USA
c
School of Environmental Sciences, University of Camerino, Italy
d
Department of Sciences, University of Basilicata, Potenza, Italy
art i cle i nfo abstract
Article history: A methodology to assess the effects of structural heterogeneities below seismic resolution in porous
Received 25 July 2013 carbonate grainstones on reservoir performance during production is developed by integrating structural
Received in revised form
analysis, power law distributions, up-scaling, and numerical techniques. The novelty of the methodology
8 November 2013 consists of accounting for the buffering effects on permeability caused by compactive and cataclastic
Accepted 9 December 2013
Available online xxx deformation bands. By using this methodology, a 3D deterministic field analogue and a 3D Discrete
Fracture Network (DFN) representations of the reservoir/aquifer were built first, and then single-phase,
steady-state fluid flow numerical experiments in an equivalent porous medium framework were per-
Keywords:
Strike-slip faults formed. The field analogue is located along the Northwestern coast of Sicily (Italy) where Lower Pleis-
Deformation bands tocene porous carbonate grainstones are crosscut by a strike-slip fault system. This fault system is made
Sub-seismic resolution faults up of two conjugate sets of strike-slip shear structures recognized as single compactive shear bands
Field analogue (CSB), zones of compactive shear bands (ZB) and well-developed faults (DF), with discrete slip surfaces
Numerical modeling and cataclastic material. The permeability of these structures is up to three orders of magnitude less than
Discrete fracture network the surrounding porous carbonate rocks. The fluid flow numerical experiments have been performed on
the two aforementioned reservoir/aquifer descriptions to assess the effect of Sub-Seismic Resolutions
Faults (SSRF), such as those observed in the outcrops, on fluid flow during production from a well, in-
jection production in Enhanced Oil Recovery (EOR), and up-scaling to large cell size for regional flow
simulation. Comparison of draw-down modeling in the DFN and the deterministic models show that
results are similar with the exception of wells located in areas of intense strain localization with ZB and
DF. The use of the DFN model is therefore an acceptable representation of the heterogeneities induced by
SSRF in a reservoir/aquifer. Results of numerical computations show that, in structurally complex areas,
SSRF-related ZB and DF might represent a drilling risk because they can enhance draw-down during
production and EOR activities.
Ó 2013 Elsevier Ltd. All rights reserved.

1. Introduction sealing within a reservoir due to their geometry, high density, and
connectivity (Agosta et al., 2010; Ambrose et al., 2008; Ballas et al.,
Sub-Seismic Resolution Faults (SSRF), also called sub-seismic 2013; Cello et al., 2001; Damsleth et al., 1998; Esposito et al., 2010;
faults, are small offset faults that cannot be imaged on seismic Maerten et al., 2006; Manzocchi et al., 2008; Walsh et al., 1998;
reflection profiles processed with standard and enhanced tech- Yielding et al., 1992). According to kinematics, amount of offset,
niques (Childs et al., 1990; Walsh et al., 1998). The maximum ver- deformation mechanisms, burial conditions and diagenetic evolu-
tical resolution obtained nowadays by seismic line processing is in tion that characterize these features, SSRF may enhance (when
the order of 5e10 m (Hustoft et al., 2007). Despite their elusive associated to predominant dilational fracturing), buffer (cataclasis)
characteristics, SSRF may have a strong impact on fluid flow and or prevent (clay smearing, compaction) fluid flow in a reservoir
(Agosta et al., 2012; Antonellini and Aydin, 1995; Ballas et al., 2013;
Fachri et al., 2013; Faerseth et al., 2007; Fossen and Bale, 2007;
Yielding et al., 1997; Manzocchi et al., 2008; Morris et al., 2012;
* Corresponding author. Tel.: þ39 339 4978001.
E-mail address: m.antonellini@unibo.it (M. Antonellini). Rotevatn et al., 2009; Tondi, 2007; Walsh et al., 1998). Different
0264-8172/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.marpetgeo.2013.12.003

Please cite this article in press as: Antonellini, M., et al., Fluid flow numerical experiments of faulted porous carbonates, Northwest Sicily (Italy),
Marine and Petroleum Geology (2013), http://dx.doi.org/10.1016/j.marpetgeo.2013.12.003