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Research

Ongoing Projects

We are currently working on:

  • Methane hydrates: predicting the fate of frozen methane in marine and permafrost environments under climate warming.
  • Geologic carbon sequestration: improving our engineered capability to safely store CO2 underground away from the atmosphere.
  • Hydrology in extreme environments: understanding the fate of water in warming cryosphere and drought-prone drylands to decide how we as a society should preserve and adapt.
  • Lava flow: developing a simplified model of how molten rock spreads on planetary surfaces.

Below you can learn more about some of the topics we have been exploring extensively.


Methane Hydrates and Crustal Fingering

crustal fingering experiments

Methane hydrate is an ice-like solid that forms out of an aqueous solution of water and dissolved methane under moderate pressure and low temperature conditions. It is most commonly found in deep marine settings (>600m water depth) and permafrost regions on Earth. A large body of work over the past few decades has established a fundamental understanding of methane hydrate equilibrium thermodynamics. However, modeling nonequilibrium behaviors in hydrates remains challenging.

In this series work, we first develop a continuum-scale phase-field model to study gas–liquid–hydrate systems far from thermodynamic equilibrium. This modeling framework, in combination of a series of high-pressure microfluidic experiments, has then allowed us to study the nonequilbrium mechanics of gas percolation through the porous sediment under hydrate-forming conditions.

We uncover a phenomenon, which we call crustal fingering, that helps explain how, counterintuitively, hydrate formation may facilitate instead of prevent methane gas migration through deep ocean sediments.

  • Crustal fingering facilitates free-gas methane migration through the hydrate stability zone; X. Fu*, J. Jimenez-Martinez*, T. P. Nguyen, J. W. Carey, H. Viswanathan, L. Cueto-Felgueroso, and R. Juanes, Proceedings of the National Academy of Sciences, (2020)
    * Equal contribution
  • Xenon hydrate as an analogue of methane hydrate in geologic systems out of thermodynamic equilibrium; X. Fu, W. F. Waite, L. Cueto-Felgueroso and R. Juanes; accepted in Geochem. Geophys. Geosyst. (2019).
  • Nonequilibrium thermodynamics of hydrate growth on gas–liquid interface; X. Fu, L. Cueto-Felgueroso, R. Juanes; Phys. Rev. Lett.,120(14):144501 (2018); [pdf]
    * Editor's suggestion
  • Laboratory observations of the evolution and rise rate of bubbles with and without hydrate shells; W. F. Waite, T. Weber, X. Fu, R. Juanes, C. Ruppel; Proceedings of the 9th ICGH (2017);

Multiphase flow in porous media with phase transitions

Ostwald Ripening

In this series work, we study the evolution of binary mixtures far from equilibrium, and show that the interplay between phase separation and hydrodynamic instabilities in porous media give rise to new nonequilibrium phenomena. Specifically, we show that:

  • viscously unstable flow can arrest the Ostwald ripening process characteristic of non-flowing mixture;
    • Thermodynamic coarsening arrested by viscous fingering in partially miscible binary mixtures; X. Fu, L. Cueto-Felgueroso, R. Juanes; Physical Review E, 94(3),033111(5) (2016); [pdf][video1][video2]​
  • fluid-fluid partial miscibility exerts a powerful control on the degree of viscous fingering;
    • Viscous fingering with partially miscible fluids; X. Fu, L. Cueto-Felgueroso, R. Juanes; Phys. Rev. Fluids, 2(10):104001 (2017); [pdf]​
  • pore-scale wettability and microstructure influences the morphology and dynamics of evaporative gas flow.
    • Pore-scale modeling of phase change in porous media; L. Cueto-Felgueroso, X. Fu, R. Juanes; Physical Review Fluids, 3, 084302 (2018). [pdf]

Geologic carbon sequestration

Convec Mix Pattern

Geologic carbon dioxide sequestration entails capturing and injecting CO2 into deep saline aquifers for long-term storage. The injected CO2 mixes with groundwater, forming a mixture that is denser than the initial groundwater. The local increase in density triggers a gravitational instability at the boundary layer that further develops into columnar plumes of CO2-rich brine, a process that is referred to as convective mixing and greatly accelerates solubility trapping of CO2. Here, we investigate the pattern-formation aspects of convective mixing along with rock-altering reactions during geological CO2 sequestration by means of high-resolution three-dimensional simulations and analogue laboratory experiments.

  • Dissolution patterns from geochemical reactions during convection mixing in porous media; X. Fu, L. Cueto-Felgueroso, D. Bolster, R. Juanes; Journal of Fluid Mechanics, 764:296-315 (2015); [pdf]
  • ​Pattern formation and coarsening dynamics in three-dimensional convective mixing in porous media; X. Fu, L. Cueto-Felgueroso, R. Juanes; Philosophical Transactions of the Royal Society A, 371:20120355 (2013); [pdf][videos]