Numerical Study of Stress Dependency of Absolute and Relative Permeability in Unconsolidated Sands

ABSTRACT: Understanding the stress dependency of absolute and relative permeability in reservoir rocks is crucial to study subsurface fluid flow. Unconsolidated sands usually have a high stress sensitivity compared to other rock types. However, unconsolidated rocks often fall apart when being tested and therefore one may not get usable results from laboratory experiments. This study employs a digital rock workflow to simulate the stress dependency of fluid flow properties by coupling a finite element analysis (FEA) micro-mechanics model with a Lattice Boltzmann (LB) fluid flow model. The numerical model is validated against laboratory measurements of stress-dependent porosity and permeability in Ottawa unconsolidated sands. The results demonstrate that increasing stress alters pore connectivity and reduces porosity and absolute permeability. The simulations indicate that relative permeability of the non-wetting phase tends to decrease with increasing stress. However, relative permeability of the wetting phase may increase or decrease conditioned by the capillary number and viscosity ratio. This study highlights the critical role of pore-scale interactions in stress-permeability relationships and provides a framework for predicting subsurface fluid behavior in unconsolidated formations. These findings have significant implications for reservoir characterization and geomechanical applications.