Methods for studying two-phase flows in porous media: Numerical simulation and experiments on microfluidics chips

Abstract

Copyright 2020, Society of Petroleum Engineers. In this paper, experimental and computational approaches are used to study multiphase flows. In the firstmethod, filtration experiments are carried out using microfluidics technology. Microfluidic chips weremade from polydimethylsiloxane using soft lithography. To give the desired surface properties, the innerwalls of the channels were treated with a hydrophobic or hydrophilic coating. Injection of liquids wascarried out using a syringe pump at a constant flow rate. To measure the pressure difference at the inletand outlet of the microchip, we used the method of measuring changes in gas volume. For numericalmodeling, the most modern model of the Boltzmann lattice equations, adapted for two-phase flows ofincompressible immiscible liquids, is used. The effects that occur at the phase boundary are described usingthe color field gradient model. Experimental studies have shown the possibility of studying the processesof liquid displacement from the microchannel system in a microfluidic chip simulating a porous medium.The dynamics of the displacement of liquids (water and oil) from a system of microchannels with differenthydrodynamic drag cardinally depends on the angle of wettability of its walls. In the case of microchannelswith hydrophilic walls, a complete displacement of oil by water occurs almost simultaneously from bothchannels. When water is displaced by oil from channels with a hydrophilic and hydrophobic coating, it isrequired to create an increased flow rate of the displacing liquid through microchannels. In this case, at thejunction of the microchannels, before leaving the chip, emulsion droplets of "water in oil" will form. Inthe case of oil displacement by water from microchannels with a hydrophobic coating, complete removalof oil from the channel with high resistance did not occur. This is due to the fact that the viscosity of theoil is 30 times higher than the viscosity of water. The paper shows a successful comparison of the resultsof numerical modeling and experimental research in a two-phase flow in a pore doublet. Demonstratedexamples of the developed program code are shown: the formation of emulsions at high flow rates, themotion of a drop under the influence of mass force; flow in digital microtomographic image; displacementof viscous oil from the pore medium.