3D numerical modeling and simulation of the impact of fault zones on fluid flow in sandstones of the Rio do Peixe Basin, NE Brazil

Abstract

Deformation bands are usually responsible for up to 3 orders of magnitude reduction in permeability perpendicularly to the structure planes, while the fault core represent a reduction of up to 7 orders of magnitude in cross-fault permeability, imposing large anisotropies to fluid flow. As deformation bands occur distributed along the damage zone, they impact not only the across-fault flow, but also the along-fault flow. The fault core is usually represented by fault transmissibility multipliers (TMs), along the fault planes, using well established workflows. However, there is a lack of methods to represent fault damage zones in any direction and grid cell sizes. In this context, we proposed new methods to: (1) estimate the deformation intensity in damage zones; (2) calculate their most representative value within the cell domain; (3) calculate the equivalent permeability of a cell containing oblique deformation bands. The workflow is applied to the 3D numerical model of the Santa Helena High, in Rio do Peixe Basin, NE Brazil. We performed streamline simulations in 4 models to evaluate the impact of fault damage zones and the fault core in fluid flow. Our models show that the fault core and damage zone negatively affected the performance of the reservoir. Supplementary material: Appendix A, describing the method developed to estimate the deformation intensity in damage zones, and Appendix B, describing the method develop to calculate the equivalent permeability, are available at https://doi.org/10.6084/m9.figshare.c.6251469