EXPERIMENTAL INVESTIGATION OF GAS/WATER/ROCK INTERACTIONS RELEVANT TO GEOLOGICAL CO2 SEQUESTRATION

A great deal is already known about the thermophysical properties of the CO₂ - water system as a function of temperature, pressure, and salinity. Critical experimental data, however, are still lacking in the PTX range relevant to CO₂ sequestration in deep saline aquifers. Considerable uncertainties also exist when the complexities of multi-component salinity are considered. A large number of additional uncertainties are associated with the heterogeneous reactions which may occur in deep aquifers upon CO₂ injection, especially in the area of reaction kinetics. An ongoing project at the National Energy Technology Laboratory (NETL) focuses on the complex solution chemistry of CO₂ in brines and the special types of analyses required to study their kinetics, and on the carbonate and silicate mineral formation/dissolution reactions which may be important in geologic sequestration in deep saline aquifers. The facilities to conduct hydrothermal CO₂-water-rock reactions and analyze these complex mixtures have been developed at NETL. In order to study the reaction kinetics of these systems, rapid analysis of meta-stable solutions may be required in addition to standard analytical methods and techniques. The rocking autoclave for the hydrothermal reactions and each of the key instruments for characterization of the brines, mineral components, and reaction products will be described. Experimental results from this investigation will be integrated with geochemical modeling studies and field studies.