Ph.D. Thesis Defense Announcement

Energy Fluids in the Subsurface - Gas, Multiphase Fluids and Particles at Interfaces

By: Jun Yeop Yeo

Advisor:  Dr. J. Carlos Santamarina

Dr. Susan Burns, Dr. Sheng Dai, Dr. Majid Hassanizadeh, Dr. Hussein Hoteit

SEB 122
https://gatech.zoom.us/j/99285990458

2026-11-17 12:00 PM EST

Fluid-liquid and fluid-mineral interactions govern subsurface resource recovery, underground energy storage, and the long-term isolation of energy-related waste, from CO₂ to nuclear waste. Various energy fluids are involved in subsurface energy systems. Curated datasets compile fluid properties that govern advection, convection, diffusion, dissolution, adsorption, and interfacial phenomena over broad ranges of pressure and temperature. These datasets provide a foundation to assess transport processes and their implications for subsurface energy applications in both onshore and offshore settings. Gas flow differs fundamentally from the flow of nearly incompressible liquids because gas density, viscosity, and compressibility vary significantly with pressure. At the molecular scale, gas transport through porous media involves collisions between gas molecules and solid boundaries. Based on this framework, a new gas-flow model is developed and experimentally validated through high-pressure flow tests in micron-diameter tubes. The model captures the behavior of various energy-related gases, including conditions that involve phase transitions. Underground gas storage relies on cushion gas to minimize pressure fluctuations and provide a buffer between the working gas and formation fluids. Yet, working gas inevitably mixes with cushion gas within porous media. Experiments in long vertical pressure vessels under high-pressure conditions reproduce quasi-reservoir-scale gas mixing for different gas pairs and injection regimes. Numerical simulations with an advection-diffusion-dispersion model identify the governing parameters and reconstruct the spatiotemporal evolution of mixing. Results reveal the combined influence of cushion-gas properties, diffusion, flow-rate-dependent dispersion, and flow direction on gas mixing. Fluid-liquid displacement in porous media depends on the relative affinities of the fluids for mineral surfaces. Advancing and receding interfaces exhibit contact angle hysteresis associated with contact-line pinning. Measurements of asymptotic advancing and receding contact angles reveal substantial hysteresis, greater than previously inferred from tilting-plane studies. Pore-network modeling extends local contact-line phenomena to the scale of porous networks and reveals causal relationships between contact angle hysteresis, residual trapping, and the asymmetry between fluid invasion and drainage. Interfacial phenomena become more complex in the presence of solid particles. Particles trapped at fluid-liquid interfaces adopt energy-minimizing configurations and can self-assemble into rafts and shells. Experiments reveal how particle shape and fluid preference govern the equilibrium position of individual particles, their collective self-assembly, and the resulting interfacial structures. These particle shells alter droplet stability and coalescence. Together, these studies advance our understanding of the physical processes that govern gas and multiphase fluid transport in porous media. They provide new experimental data, predictive models, and fundamental insights across multiple scales, with relevance to subsurface energy applications.