Upscaling of Sub-Seismic 3D Fault Zone Structure: A Comparison Between Template-Based and Flow-Based Geometrical Upscaling Approach

Islam, M. S. (Dhofar University in Oman and Fault Analysis Group, UCD School of Earth Sciences, University College Dublin in Ireland) | Manzocchi, T. (Fault Analysis Group and Irish Centre for Research in Applied Geosciences, UCD School of Earth Sciences, University College Dublin)


Most petroleum reservoirs contain faults, and a major technical challenge in full-field flow simulation is to represent the effects of 3D fault zone structure within the 2D fault surface represented in the industry standard commercial simulator. Geometrical upscaling (GU) is sometimes performed to include these fault zones implicitly in the upscaled model, and in this study, a comparison is made of the accuracy and flexibility of different geometrical upscaling methods. The existing template-based geometrical upscaling (TBGU) method is compared to a new flow-based geometrical upscaling (FBGU) method. In both methods, the faults are represented in the upscaled flow 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 flow simulation model (referred as truth model in this paper) containing complex 3D sub-seismic fault zone structure explicitly, which is then upscaled using the two methods to take into account the influences of the fault zone geometry as across-fault and along-fault flow. The accuracy of the upscaling methods is examined by comparing the flow behavior of the high-resolution flow simulation model with that of model versions upscaled in the two different ways. Individual well performance for the high-resolution truth and the upscaled models reveal significant differences between the two methods, and indicate that the flowbased geometrical upscaling technique is a more accurate means of including structurally complex fault zones into low-resolution upscaled flow simulation model.