A multiphase level set approach to motion of disconnected fluid ganglia during capillary-dominated three-phase flow in porous media: Numerical validation and applications

We present a multiphase level set (MLS) approach to capillary-controlled, three-phase displacement in porous media, and use it to simulate displacements of disconnected fluid ganglia surrounded by two other fluid phases (i.e., double displacements), which are important pore-scale mechanisms for oil recovery and CO2 storage. After a comprehensive model validation on several new benchmark cases, including 3-D simulations of double displacements in a straight angular tube, we show two new applications of the MLS method. First, we simulate three-phase capillary pressure curves for gas invasion along constant oil saturation paths in sandstone. The results show significant oil redistribution by double displacements, which leads to fluctuations of gas/oil capillary pressure due to oil volume preservation, whereas oil/water capillary pressure increases mostly monotonically, yet the pressure level is lower than in the corresponding two-phase oil/water system. Further, gas/water capillary pressure is lower when mobile oil is present in the sample. The second application demonstrates the suitability of MLS method to describe foam dynamics both with and without oil present in the pore space. MLS method successfully describes well-known foam interfacial properties, and it also captures the rise of displacement capillary pressure when adding gas bubbles between continuous gas and water inside a pore channel. (C) 2019 Elsevier Ltd. All rights reserved.