Using the fluctuation-dissipation theorem to measure total phase mobility during fractional flow experiments

This study investigates the application of the Fluctuation-Dissipation Theorem (FDT) to predicttotal phase mobility in two-phase flow experiments through porous media. We show that flux-fluctuationsobserved during steady-state multiphase flow can effectively predict total phase mobility. By analyzingthese fluctuations under varying fractional flows (Fw), we construct a saturation versus total phase mobilityplot and compare the results with experimental measurements obtained using Darcy’s law. Additionally, theexperimental system was imaged using X-ray computed microtomography, followed by image segmentationto enable direct pore-scale simulations. These simulations were used to measure relative permeability, andthus total phase mobility, offering a complementary approach to the experimental data. The agreementbetween simulations and experiments supports the use of FDT for measuring total phase mobility inmultiphase flow systems. In general, our work highlights the potential of the FDT to convert commonlyobserved phase fluctuations into quantitative measures of total phase mobility, providing a novel approachto characterizing multiphase flow behavior.