HR: 1340h
AN: U43C-1383    [Abstracts]
TI: A KEY FOR ‘STABLE' SEQUESTRATION OF CO2 IN GEOLOGICAL RESERVOIRS: THE FORMATION OF CARBONATE MINERALS
AU: Lopez, O
EM: lopez@ipgp.jussieu.fr
AF: Institut de Physique du Globe de Paris, 4, place Jussieu, Paris, F75005, France
AU: * Zuddas, P
EM: zuddas@ipgp.jussieu.fr
AF: Institut de Physique du Globe de Paris, 4, place Jussieu, Paris, F75005, France
AB: CO2 injections in brine aquifers strongly modify the physic and the chemistry of the host aquifer affecting mainly the calcite precipitation kinetics. Classically precipitation laboratory experiments link the precipitation rate (the dependent variable) to one or more independent variables. In this work we evaluated the mutual influence of pCO2 partial pressure, temperature, ionic strength (or salinity), major components and known calcite inhibitors (Mg, SO4, dissolved organic matter) in the complex calcite formation process under pertinent geological CO2 sequestration conditions. An inversion model of experimental kinetic rate data has been developped to link the precipitation rate of calcite of the independent variables and physico-chimal parameters. Using a multidimensional least squares regression method we generate a general multivariable equation of the form: dobs = G.m Where dobs is the column matrix representing the experimental precipitation rates (in the logarithm scale) and G is a matrix containing all the experimental parameter values (temperature, pCO2, activity of inhibitor and accelerators, ionic strength). The m term is also a column matrix corresponding to the value (weight) affected by each parameter and evaluated by the kinetic data inversion. Scenarios resulting from mixing of fluids in the aquifer and others enriched in CO2 show an rapid initial enhancement of the carbonate precipitation rate. However, when pCO2 and salinity decrease the calcite kinetic rate is inhibited and the rate is not ruled by simple affinity (i.e. [CO3]) laws. We observed an intermediate stage where the rate of calcite precipitation is low because of inhibiting influence of the salinity. In a final stage, the neutralisation of the fluid acidity by the rock dissolution generates a higher saturation state of the fluids that with a high carbonate ion concentration (from 0.90 to 2.5 mmol/kg) is responsible for 3 orders of magnitude increase of the calcite precipitation rate. Our results clearly identify the kinetics and thermodynamics role on the major parameters that drive the carbonate precipitation reaction.
DE: 3610 Geochemical modeling (1009, 8410)
DE: 4251 Marine pollution (0345, 0478)
DE: 8410 Geochemical modeling (1009, 3610)
SC: Union [U]
MN: 2007 Fall Meeting