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Cataclastic deformation bands, which are common in sandstone reservoirs and which may negatively affect fluid flow, are generally associated with notable thickness variations. It has been suggested previously that such thickness variations represent an important control on how deformation bands affect fluid flow. The effects of such thickness variations are tested in this study though statistical analysis and fluid flow simulation of an array of cataclastic deformation bands in Cretaceous sandstones in in the Bassin de Sud‐Est in Provence, France. Spatial outcrop data are statistically analyzed for incorporation in flow simulation models, and numerical simulations are used to investigate the effects of notable thickness variations on how the deformation bands influence effective permeability and flow dynamics. A suite of simulations is performed using a combination of fine‐scale and coarse‐scale grids, revealing that the effective permeability of the simulated reservoir is reduced by a factor of 15–25. More interestingly, the simulations further demonstrated that, as compared to the overall effect of the deformation band array on fluid flow, thickness variations along the bands proved to have negligible effects only. Thus, our simulations indicate that the configuration and connectivity of the deformation bands, together with the permeability contrast between the bands and the host rock and the mean band thickness, are the most important controls on the effective permeability. Our findings represent new insight into the influence of deformation bands on fluid flow in subsurface aquifers and reservoirs, indicating that thickness variations of individual deformation bands are of less significance than previously thought.

Discrete fracture models are an attractive alternative to upscaled models for flow in fractured media, as they provide a more accurate representation of the flow characteristics. A major challenge in discrete fracture simulation is to overcome the large computational cost associated with resolving the individual fractures in large-scale simulations. In this work, two characteristics of the fractured porous media are utilized to construct efficient preconditioners for the discretized flow equations. First, the preconditioners are tailored to the fracture geometry and presumed flow properties so that the dominant features are well represented there. This assures good scalability of the preconditioners in terms of problem size and permeability contrast. For fracture dominated problems, numerical examples show that such geometric preconditioners are comparable or preferable when compared to state-of-the-art algebraic multigrid preconditioners. The robustness of the physics-based preconditioner for less favorable fracture conditions is further demonstrated by a systematic degradation of the fracture hierarchy. Second, the preconditioners are physics preserving in the sense that conservative fluxes can be computed even for an inexact pressure solutions. This facilitates a scheme where accuracy in the linear solver can be traded for efficiency by terminating the iterative solvers based on error estimates, and without sacrificing basic physical modeling principles. With the combination of these two properties a novel preconditioner is obtained which bridges the gap between multiscale approximations and iterative linear solvers.