Sensitivity of fluid flow to deformation-band damage zone heterogeneities: A study using fault facies and truncated Gaussian simulation

We demonstrate that truncated Gaussian simulation (TGS), which is typically used for modeling of sedimentary rocks, can be employed to reproduce detailed damage zone structure as observed in outcrops. The basic modeled units employed are fault facies classified according to deformation density. Published damage zone field maps are re-drawn as fault facies maps and used for deriving geostatistical descriptions of model input parameters. We apply the modeling method for damage zones related to three scenarios: an isolated fault, branching faults and double-tip interacting faults. Constrained by the resulting TGS models, a series of damage zone permeability models are generated by systematically modulating five modeling factors related to different heterogeneity scales. Single-phase flow simulations reveal that fault facies proportion and damage zone width are the most influential factors, followed by deformation band frequency. Deformation band permeability and fault facies extent are the least important factors. Modifying fault facies proportion and damage zone width mainly change the flow retardation/enhancement in the models, whereas modifying deformation band frequency, deformation band permeability and fault facies extent mainly change the flow tortuosity in the models. Finally, we examine hierarchical modeling and upscaling procedures to incorporate our fine-scale models into flow simulation models.