Abstract - Most petroleum reservoirs contain faults, and a key methodological challenge in full-field reservoir
modeling is to include the effects of 3D sub-seismic fault zone structures within the 2D fault surface represented in the
commercially available simulators. To address this shortcoming, connectivity-based geometrical upscaling (GU) is
introduced to include these fault zones implicitly in the upscaled reservoir model, and in this study, a comparison is
made of the accuracy and flexibility of two different GU methods. The existing template-based geometrical upscaling (TBGU)
method is compared to a newly developed flow-based geometrical upscaling (FBGU) method. In both methods, the faults and
their associated single-phase fault rock properties are represented in the upscaled reservoir simulation model
implicitly as neighbor and non-neighbor cell-to-cell connection transmissibilities, which are determined from 3D fault
zone structures, but these transmissibilities are calculated in very different ways. Both approaches require a
high-resolution reservoir model (e.g., truth model), contains 3D fault zone structure explicitly within the model
geometry, which is then upscaled using the two methods to take into account the influences of the fault zone structure.
The accuracy of both the upscaling methods is examined by comparing the flow behavior of the truth model with that of
model versions upscaled using two different ways. The results of the two versions of upscaled models revealed significant
differences, and indicate that the FBGU technique is an accurate and flexible means of including structurally complex
fault zone into low-resolution upscaled reservoir simulation models.
Natural Resources Research, 30, 2021. https://doi.org/10.1007/s11053-021-09832-6