Deformation bands and their impact on fluid flow: Insights from geometrical modelling and multi-scale flow simulations in sandstones

Deformation bands may show permeabilities that are a few orders of magnitude lower than the surrounding host rocks and therefore have a negative impact on fluid flow in sandstone hydrocarbon reservoirs. Understanding the geometrical attributes of individual bands and their patterns is a critical step in quantifying their connectivity and interpreting how they may compartmentalise reservoirs in the subsurface. In order to gain insights into the shapes, cross-cutting relationships and connectivity of these structures, we developed 3D geometrical models (scaled to centimetres) of deformation bands and joining ladder structures, using a sliced small-scale rock sample from outcrops at Hopeman, Moray Firth (Scotland) and near Goblin Valley, Utah (USA). This 3D geometrical model is used for two-phase flow simulations (water-oil and gas-oil) in order to investigate the effect of deformation bands on time to water breakthrough, waterfront propagation and sweep efficiency. We also investigated capillary effects on flow. Flow simulation results show that the presence of deformation bands led to various time to water and gas breakthroughs, irregular shape of water and gas front propagation and various sweep efficiency for different flow-system. Furthermore, understanding the dynamic behaviour of flow through these structures can lead to better predictions of the influence of deformation bands on fluid flow in subsurface reservoirs.