Fault
Impact on Reservoir Performance: A Synthetic Case Study of Host Rock Sand Lenses in
Fault
Cores
Niclas Fredman1, Jan Tveranger1, Siv Semshaug1, Alvar Braathen1, and Einar Sverdrup2
1 Center for Integrated Petroleum Research, Unifob, University of Bergen, Bergen, Norway
2 Roxar Software Solutions, Oslo, Norway
We present a synthetic study on fault
impact in siliciclastic reservoirs using a volumetrically defined
fault
.
Normally, simulation models of faulted reservoirs include faults as grid offset in combination with transmissibility coefficients. This approach tends to ignore the actual 3D architecture of fault
zones commonly seen in seismic scale faults. Representing faults as 3D rock volumes in reservoir models may capture effects which are presently overlooked and possibly yield a more realistic description of the structural heterogeneities.
An experimental, synthetic 3D model with a single normal fault
was constructed by defining a fine grid around the
fault
plane. The
fault
grid was subsequently populated with two conceptual
fault
rock types; host rock sand lenses and
fault
gouge. The
fault
gouge permeability and host rock sand lens permeability were systematically varied between 0.01-1 mD and 50-500 mD, respectively. A total of 480 realizations were generated and flow simulated.
Simulation results show, among other results: (i) host rock sand lenses in contact with undeformed host rock can constitute an important flow path through faults, especially when the fault
gouge matrix permeability is low. (ii) As the
fault
gouge matrix permeability is increased towards 1 mD, the host rock lenses become less important as flow paths and the
fault
gouge matrix permeability is becoming more important. (iii) Host rock lenses not in contact with undeformed host rock do not appear to affect fluid flow significantly.