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.
Modelling a strike-slip fault system affecting porous carbonates in Favignana Island (Sicily, southern Italy)
CILONA, ANTONINO;TONDI, Emanuele;AGOSTA, FABRIZIO;
2013-01-01
Abstract
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.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
