MODELING MULTIPHASE FLUID REACTION PROCESSES INVOLVING SUPERCRITICAL CARBON DIOXIDE

Low to moderate grade metamorphism, flow and transport in metamorphic rocks, and fluid inclusions, often indicate substantial mobility and reactivity of carbon dioxide.  Laboratory and industrial uses of supercritical carbon dioxide have become extensive in recent years, and provide new information and concepts relevant to geologic systems.  As a result, supercritical carbon dioxide phase reactive properties and complex mixtures that can coexist at relatively moderate temperatures/pressures are beginning to be appreciated in a broad range of geologic systems.

Simulation of reaction processes involving solution, minerals and a separate carbon dioxide phase requires consideration of geochemistry that has not been widely captured modeling code systems.  Two specific aspects necessary to simulate this system have been developed in this research: multi-phase composition changes, and solution solute precipitation reactions.  Both aspects were developed using existing simulation code systems.  Initial systems investigated are ordinary Portland cement reactions, and pressure dependent phase fractionation for H₂O-CO₂-salt systems.  Experimental characterization and video observation of dynamic processes has been collected in supercritical CO₂ industrial reactors.  Subsequently, exploration of calculated reaction paths, including phase equilibria of immiscible carbon dioxide and water has allowed evaluation of coupled reaction processes and insight into influence of two fluid phases on mineral equilibria occurring in experimental geochemical reactions.

Our research initially focused on the developing issues of anthropogenic carbon dioxide sequestration.  Classic questions of the transport, reaction processes and distribution of carbonate minerals, cements and veins in a diverse set of geologic environments are developing new, broader, hypotheses.  The diverse presence of carbonate rocks in the Earth’s crust, provide ample availability for dynamic hydrothermal and metamorphic systems.