Leonardo Guimarães

Federal University of Pernambuco

Modeling and simulation of deformation bands and natural fracture network effects on fluid flow

Models that predict permeability by considering analogues have been used to enhance the understanding of the relative contribution of deformation bands and fracture networks to reservoir quality. The analogue data can overcome scale limitations (sub-seismic to mm) and/or lack of consistency in subsurface datasets (e.g., seismic data, well logs, and cores). Fluid flow modeling of naturally fractured reservoirs remains a challenge because of the complex nature of fracture systems controlled by various chemical and physical phenomena. A discrete fracture network (DFN) model represents an approach to capturing the relationship of fractures in a fracture system and topology represents the connectivity aspect of the fracture planes, which have a fundamental role in flow simulation in geomaterials involving fractures and the rock matrix. On the other hand, deformation bands are subseismic brittle structures with tabular geometries that accommodate small shear offsets, occurring as either single structures or cluster zones (where slip surfaces can initiate), associated with the process of faulting in porous rocks and sediments (>15% porosity) due to grain rearrangement and strain softening, affecting the petrophysical properties of host rocks. Deformation bands can influence fluid flow within reservoirs, mainly acting as flow barriers. We used the finite element method for modeling the fracture system, with the incorporation of discontinuities for the representation of fractures in the medium. It has been shown the influence of fractures interconnection degree (topological patterns) on the equivalent permeability of the fractured medium. Our petrophysical analysis showed that samples affected by deformation bands have lower porosity (by up to two orders of magnitude) and permeability (by up to four orders of magnitude) values than samples collected in the host rocks. Numerical fluid flow simulation allowed us to conclude that the deformation bands act as partial flow barriers where the hydraulic head can indicate the barrier effect intensity.