3D Geomechanical Reservoir Modelling in Faulted Reservoirs

Abstract

Abstract In this study, we present a three-dimensional (3D) geomechanical reservoir model for a faulted and compartmentalized reservoir in the Eastern Mediterranean. A series of alternative production scenarios performed using a simulation model that accounts for consolidation and plasticity deformation of the rocks. Plastic yielding is mainly developed in fault slip zones of narrow extent whereas it appears that there is low risk of plastic behavior in the main reservoir. The slip conditions become complex in the fault contact surfaces where local areas close to fault connections are more pronounced to slip creating localized areas of smaller faulted zones. Displacement magnitudes, are controlled by the structural boundary conditions and the geometrical shape of each fault block. Overall, the higher displacements develop in the near fault region while in the remote from the fault area the vertical displacement is nearly constant as it is clearly governed by the reservoir depletion. Furthermore, changes of normalized permeability can be drawn in the 3D space providing additional insights of heterogeneous distribution. Introduction Petroleum geomechanics become important in reservoirs highly impacted by faults mechanics and overpressure zones. An operator has to well define the fault structural geometry of the field and assess early in the producing life of a reservoir whether production will be affected by the presence of naturally occurring fractures though some faults and fractures cannot be identified even at the early stages of a field production. Reservoir depletion increases the stress carried by the load-bearing grain frame of the reservoir rock. Stress analysis can be extended to identify rock failure conditions that can lead to the creation of new faulted systems in the subsurface formations. Geomechanics play an important role in identifying the stress conditions in a faulted reservoir system and the potential of slip activation of an existing fault. Extensive accounts on the importance of reservoir geomechanics can be found in the classical books of Fjaer et al., (2008) and Zoback, (2010). Finite element analysis can be used to simulate the tectonic movement to match borehole observations (Plumb et al., 1998).