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 predict
total phase mobility in two-phase flow experiments through porous media. We show that flux-fluctuations
observed during steady-state multiphase flow can effectively predict total phase mobility. By analyzing
these fluctuations under varying fractional flows (Fw), we construct a saturation versus total phase mobility
plot and compare the results with experimental measurements obtained using Darcy’s law. Additionally, the
experimental system was imaged using X-ray computed microtomography, followed by image segmentation
to enable direct pore-scale simulations. These simulations were used to measure relative permeability, and
thus total phase mobility, offering a complementary approach to the experimental data. The agreement
between simulations and experiments supports the use of FDT for measuring total phase mobility in
multiphase flow systems. In general, our work highlights the potential of the FDT to convert commonly
observed phase fluctuations into quantitative measures of total phase mobility, providing a novel approach
to characterizing multiphase flow behavior.