Rapid MRI profiling of two-phase flow in porous media

Abstract

Two-phase flow in porous media underpins a wide range of natural and industrial processes, but its transient dynamics remain challenging to capture at the spatiotemporal resolution required to resolve pore-scale phenomena. We present a method for rapid one-dimensional (1D) magnetic resonance imaging (MRI) profiling that simultaneously acquires spin-echo signal intensity and phase angle profiles with $98\mathrm{\mu m}$ spatial and $20\mathrm{ms}$ temporal resolution. The technique enables real-time observation of both fluid saturation and velocity fluctuations across a porous medium. We demonstrate its capabilities through three benchmark experiments: (1) controlled drainage and filling of a cylindrical tank, (2) buoyancy-driven rise of oil droplets in water, and (3) drainage and imbibition of a model porous medium. The results reveal dynamic interfacial behavior, velocity fluctuations linked to Haines jumps, and flow-dependent signal attenuation effects. We further analyze the relationship between flow velocity and signal attenuation in porous media using stop-motion dual-echo experiments. Our findings show that rapid magnetic resonance imaging provides a sensitive tool for probing two-phase flow dynamics, with implications for understanding complex fluid behavior in porous materials.