CO₂ Sequestration in Saline Aquifer: Geochemical Modeling, Reactive Transport Simulation and Single-phase Flow Experiment

Storage of CO₂ in saline aquifers is one way to limit the buildup of greenhouse gases in the atmosphere. Large-scale injection of CO₂ into saline aquifers will induce a variety of coupled physical and chemical processes including multiphase fluid flow, solute transport, and chemical reactions between fluids and formation minerals. These issues were addressed using CO₂ solubility modeling, simulation using geochemical reaction, 1-D reactive transport and Particle Image Velocimetry (PIV).

Comparison of CO₂ solubility model against experimental data suggest that Duan and Sun (2003) CO₂ solubility model (DS-CSM) accurately modeled solubility of CO₂ in brine for range of temperatures, pressures and salinities. Modeling under equilibrium, path-of-reaction and kinetic rate using a reactor type Geochemists Workbench demonstrate that dissolution of albite, K-feldspar, and glauconite, and the precipitation of dawsonite and siderite are very important for mineral trapping of CO₂.

A 1-D reactive transport was developed based on CO₂ solubility model that take in to account the high salinity of Rose Run brine and a module that calculates the equilibrium constants based on temperature and pressure. The results indicate that the extent of sequestration through solubility and mineral trapping is sensitive to the choice of CO₂ solubility model and the fugacity of CO₂. Reactive transport modeling underscores in the long-run siderite and dawsonite minerals are important sink in trapping CO₂ in the Rose Run Sandstone but over a short time-scale the hydrodynamic trapping plays a crucial role. The calculated storage capacity using DS-CSM suggest that for the first 100 years, 90 percent of the injected CO₂ trapped as free CO₂ whereas 6 percent are trapped in dissolve form and the rest sequestered in minerals.

Micro-scale single-phase flow through a network model of porous rock was investigated using experimental and numerical analysis. PIV with refractive index matching was developed to map velocity of pore-scale fluid flow through acrylic two-dimensional network without chemical reaction. Experimentally determined velocity vectors for single-phase flow through pore bodies and adjoining throats as well as for the outlet of the flow cell were compared with numerical simulations of flow through the cell using FLUENT computer code.