Incorporation of 3D Fault Zones in Field-sized Simulation Models - A First Case Study

Abstract

Conduit faults and faults that can accommodate vast long-distance along-strike flow are well-documented phenomena. In reservoir simulation models, flow within these features are more correctly captured using a volumetric representation of fault zones rather than employing 2D fault planes. We here demonstrate a method for implementing fault zone grids and features on a full-field case study. The fault zone grid is populated by fault rocks and fractures. We investigate the resulting effect on the modelled forecast of field-wide reservoir flow. Membrane slip zones cause the fault zones to form barrier-conduit systems. Along-strike positioned injector-producer pairs focus flow into the fault zone, decreasing sweep efficiency. On the other hand, injector-producer pairs positioned to drain perpendicular to faults partition the injection fluids and therefore tend to increase overall sweep efficiency. In models with conduit slip zones, the fault zones act as thief zones. Fluids preferentially move through the fault zones towards the producers. Consequently, sweep efficiency is more related to injector-producer distance than the geometric relation of well pairs to the faults. Our study suggests that the improved realism added by incorporating volumetrically expressed fault zones substantially influences forecasts of field behavior, and consequently should be considered during oil/gas production planning.