ABSTRACT: Use of Geochemical Modeling for the Prediction of CO2 Fate in Geological Reservoirs: Some Problems and Some Solutions
Understanding the fate of CO2 disposed in aquifers or depleted hydrocarbon fields requires the use of reaction-transport models, able to predict the possible interaction between gas, acidified water and minerals. Making predictions in this domain has a potential impact on the optimization of the process (mass balance of carbon vs. time) and on the confinement and safety of storage (caprock behaviour). The results delivered by reaction-transport models depend on many parameters and hypotheses, of which some are still badly constrained. An example concerns the way to transpose kinetics of mineral reaction, acquired from laboratory experiments on mineral powders under high water-to-mineral ratio, to the real rock system. The presentation focuses on the simulation of flow-through experiments designed to improve the upscaling of kinetic rates, and concerns either the problem of reactive surface areas or the influence of rock composition and mineral solubility on the water-mineral reactions. Consequences are drawn for application to several scenarii where dissolved CO2 could interact with the minerals. Both host rock and caprock are envisaged. The reliability of such simulations is tentatively discussed considering the uncertainty that can be reasonably assumed on all the kinetic parameters.
Keywords: CO2, sequestration, water-rock interaction, geochemical modeling, kinetic rates.
AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.