HR: 1340h
AN: GC13A-1216    [Abstracts]
TI: A new overall kinetic model describing calcite precipitation from brine-like solutions
AU: Charara, M
EM: charara@ipgp.jussieu.fr
AF: Institut de Physique du Globe de Paris, 4, place Jussieu, Paris, F75005 France
AU: Charara, M
EM: charara@ipgp.jussieu.fr
AF: Schlumberger, 1, rue Becquerel, Clamart, F92142 France
AU: Lopez, O
EM: lopez@ipgp.jussieu.fr
AF: Institut de Physique du Globe de Paris, 4, place Jussieu, Paris, F75005 France
AU: Lopez, O
EM: lopez@ipgp.jussieu.fr
AF: Centre de recherche IPGP-SCHLUMBERGER-TOTAL sur la sequestration geologique du CO2, 4, place Jussieu, Paris, F75005 France
AU: * Zuddas, P
EM: pierpaolo.zuddas@univ-lyon1.fr
AF: Institut de Physique du Globe de Paris, 4, place Jussieu, Paris, F75005 France
AU: * Zuddas, P
EM: pierpaolo.zuddas@univ-lyon1.fr
AF: PEPS Universite Claude Bernard Lyon 1, 43, boulevard du 11 novembre 1918, Villeurbanne, F69622 France
AU: * Zuddas, P
EM: pierpaolo.zuddas@univ-lyon1.fr
AF: Centre de recherche IPGP-SCHLUMBERGER-TOTAL sur la sequestration geologique du CO2, 4, place Jussieu, Paris, F75005 France
AB: Future CO₂ injections would modify strongly the physic and the chemistry of the brine aquifer hosts (i.e. temperature, chemical composition, PCO₂ partial pressure etc...). Although many geological systems can be represented using thermodynamic concepts and principles, the factors governing their fate and evolution can only be understood if the kinetics and mechanisms of reactions are well known. One of the most important problems in the application of carbonate fluid-rock interactions is the function governing the variation on precipitation rate. A general rate law describing the calcite precipitation is:
R=k,f(PCO₂),g(I),h(T),φ(Π a_i),φ([CO₃^2-])
where R is the precipitation rate, k is the apparent kinetic constant of caclite crystal growth, PCO₂ is the partial pressure of CO₂ at equilibrium (from 30 to 3.10⁴Pa), I is the fluid ionic strength (from 0.1 to 1 mol.kg^-1), T is the temperature (from 5 to 60°C), a_i is the activity of the specific brine constituents (accelerators, inhibitors, both organic and inorganic) and [CO₃^2-] is the concentration in carbonate ion (from 100 to 400 mmol.kg^-1) assumed to be the macroscopical variable governing the overall reaction. Based on parametric inversion of previous and new kinetic data, we established an empirical model describing the variation of calcite precipitation rate as a function of these multiset parameters and variables. The model robustness validation (square correlation coefficient of 0.95) was obtained by compairing experimental measured and calculated rates. We found that, despite temperature and fluid ionic strength rule the reaction kinetic mechanisms, the variation of PCO₂ partial pressure enhances by three orders of magnitude the rate of calcite precipitation even in completly buffered brine-like conditions. Our results indicate that, in present day sedimentary basins, the main role played by PCO₂ partial pressure is independent from the desequilibrium condition contrar to both temperature and ionic strength. Our overall kinetic model may allow to predict variations of calcite precipitation rates and reaction mechanisms in response to a CO₂ injection in brine aquifers if the physical rock properties are known.
DE: 1009 Geochemical modeling (3610, 8410)
DE: 1051 Sedimentary geochemistry
DE: 1615 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 4805, 4912)
DE: 1630 Impacts of global change (1225)
SC: Global Climate Change [GC]
MN: Fall Meeting 2005