PNNL

Abstract

Design and risk assessment of field-scale systems for injecting supercritical CO2 into deep saline aquifers demands numerical simulation of the multifluid injection process to capture the displacement of the brine with CO2, dissolution of CO2 into the brine, Rayleigh convection of the brine with CO2 dissolution, and non-isothermal effects. Critical factors for assessing the technical viability of particular injection design and sequestration reservoir include CO2 dissolution rates into the brine, spreading rates for the supercritical-CO2 bubble, chemical reactions between CO2-brine and the aquifer minerals, cap rock integrity and seismicity potential with changes in the effective stress. Applying numerical simulation techniques to the understanding of field-scale applications much simpler than those proposed for deep formation sequestration of CO2, is often complicated by uncertainties in hydrologic parameters and geologic features. Although geologic sequestration in deep aquifers offers promise for reducing emissions of anthropogenic CO2, the analytical tools used to evaluate these coupled engineered and hydrogeologic systems must provide a realistic representation of the physical and chemical processes. Assessing a numerical simulator?s ability to model the complex and coupled processes of injecting supercritical CO2 into saline aquifers benefits from having controlled hydrogeologic conditions. Numerical simulations are presented of supercritical CO2 injection experiments into idealized porous media (e.g., glass beads and quartz sands) and compared against laboratory measurements for a similar system; where the multifluid flow behavior is tracked via fluorescent inert nanoparticles. Capabilities for solving the nonlinear conservation equations for three mass constituents (i.e., water, NaCl salt, and CO2) and thermal energy have been incorporated into multifluid subsurface flow and transport simulator.