Pore-Level Network Modeling of Three-Phase Capillary Pressure and Relative Permeability Curves

Abstract

Summary A three-dimensional (3D) pore-level network model is developed to calculate three-phase capillary pressure and relative permeability curves. The model combines a description of pore space morphological features and three-phase displacement physics to model capillarity-controlled gas invasion into a water-wet medium containing oil and water. The gas/water capillary pressure curves in three-phase systems depend on the fluid saturations, the spreading coefficient, and the oil/water capillary pressure. Water relative permeability, for the strongly water-wet system modeled, is a function of its saturation alone. Gas and oil relative permeability curves depend on the gas and oil saturation, respectively, the saturation history, and the spreading coefficient. The displacement of oil as a response to changing the capillary pressure in a three-phase system cannot be described by existing models for multiphase flow. A modification of Darcy's law is proposed to describe capillary pressure induced oil transport in three-phase systems.