Genies investigates mineral crystallization in confined porous media, with emphasis on gas influence on crystallization and its effects on transport properties. Three key studies were conducted:
Study 1: Crystallization in ConfinementNucleation dictates pore structure and hydraulic pathways in rock matrices. Barite (BaSO₄) commonly forms in oil, gas, and geothermal systems, reducing permeability. While its crystallization is well-documented in batch studies, compacted rock matrices present different dynamics due to slow fluid velocities and limited water volumes. Nucleation inhibition in small pores increases barite solubility (<100 nm pores), though kinetic hindrance has also been observed, necessitating further research. Using time-resolved microscopy, optical imaging, and Raman spectroscopy, barite nucleation was analyzed in bulk and nano-confined environments. Microfluidic experiments revealed nucleation scales with solution volume, consistent with classical nucleation theory, and is significantly delayed in pores <1 µm, becoming pronounced below 0.1 µm. Unexpectedly, at low supersaturation (SI < 2.2) crystallization preferentially occurred in capillaries due to high surface area, suggesting that in nanopores, thermodynamic effects dominate, whereas in micropores, geometry and surface-driven kinetics play a key role. Ongoing research focuses on gas influence on bubble formation and mineralization.
Study 2: Crystallization Kinetics of Ra-bearing BariteRadium (Ra) isotopes (e.g. 226Ra, half-life: 1600 years) are NORMs affecting oil/gas extraction, hydraulic fracturing, and geothermal systems. Ra forms (Ba,Ra)SO₄ solid solutions, impacting wastewater treatment, site remediation, and nuclear waste repositories. To elucidate the crystallization kinetics of (Ba,Ra)SO₄, microfluidic experiments monitored by time-resolved microscopy, Raman spectroscopy, and computer vision were conducted. A microfluidic mixer precipitated Ba₀.₅Ra₀.₅SO₄ at varying saturation levels. 3D Raman tomography revealed that the {210} face grew twice as fast as the {001} face, a characteristic of barite. A custom computer vision algorithm tracked crystal growth, enabling precise kinetic parameter determination. The observed growth rate followed a second-order reaction with a kinetic constant of (1.23 ± 0.09) × 10⁻¹⁰ mol m⁻² s⁻¹. These insights are being implemented in large-scale assessments of Ra migration in fractured crystalline rocks.
Study 3: Solute Transport in Partially Saturated Porous MediaSolute transport in unsaturated porous media is critical for hydrogen storage, CO2 sequestration, groundwater contamination, and radionuclide migration. A pore-scale numerical framework using the Lattice Boltzmann Method (LBM) was developed to simulate diffusion of tritiated water (HTO) and ions in variably saturated clays. The Shan-Chen LBM was applied to model spontaneous phase separation, capturing liquid/gas distributions in 3D pore structures. An equivalent solute method was developed to stabilize numerical solutions at liquid/gas interfaces with steep concentration gradients. HTO diffusion simulations in unsaturated clays (0.5 to full saturation) showed local diffusion coefficients decrease near clay surfaces, and sharp concentration jumps at liquid/gas interfaces align with Henry’s law predictions. Furthermore, Poisson-Boltzmann-Nernst-Planck equations were used to simulate ion diffusion under electrical double layer (EDL) effects. Results indicate ion diffusion decreases more than water diffusion upon desaturation, aligning with data from compacted sedimentary rocks. Ongoing work explores diffusion in chemically evolving (due to mineral crystallization) unsaturated media.
