Scalar transport during miscible viscous fingering experiments in consolidated porous media

Miscible viscous fingering, driven by the viscosity contrast between displacing and displaced fluids, significantly impacts subsurface processes in energy and environmental applications. Prior experimental studies that relied on synthetic porous media, such as sand packs or Hele–Shaw cells, do not fully represent the impact of fingering on pressure and concentration distribution in three-dimensional geological media. In this study, we perform experiments of scalar transport during viscous fingering in consolidated Berea Sandstone cores to capture fingering dynamics. Pressure profiles are monitored using high-resolution transducers along the core length. Scalar concentrations are measured using inductively coupled plasma optical emission spectroscopy, enabling ultra-sensitive detection of fingering-induced effects in the scalar breakthrough curve. Impacts of viscosity contrast and injection flow rate on the pressure drop profile through the domain and the scalar breakthrough profile at the outlet are analyzed. Channeling of the less viscous fluid at high viscosity contrasts is identified as the primary reason for deviations between classical models and the experimental results. A numerical model calibrated with experimental data of breakthrough and pressure profiles reproduces in situ finger dynamics, enabling further investigation of mixing and spreading processes and the synthesis of an effective transverse diffusivity in terms of the transverse variance and dissipation rate of the scalar. We propose a novel workflow utilizing temporal, longitudinal, and transverse spatial moments of the concentration distribution, previously unexplored in viscous fingering studies, to systematically quantify stochastic dispersive characteristics. Ultimately, this work improves predictive modeling capabilities essential for efficient management of subsurface resources.