A reactive transport model of CO2 injection in basaltic rocks
Résumé
A CO2 injection was carried out at the Lamont-Doherty Earth Observatory site (Palisades, New York, USA) to assess the basalt neutralization capacity [1]. The essay consisted of a single-well push-pull test in which an CO2- rich solution was injected in the aquifer and pumped after a 24 days incubation period. Chloride was added as a inert tracer and 18O was measured as a second conservative tracer. We present a reactive transport model of the push-pull test made with HYTEC code [2]. Flow and transport parameters were calibrated using data from pumping and recovery tests and by fitting the chloride breakthrough curve. 18O was used to validate the calibrated parameters. The model shows that conservative tracers arrival is mainly controlled by the product of porosity times longitudinal dispersion. Chemical processes were identified using the reactive transport model. Results show that the interaction between CO2 and the basaltic host rock is governed by the kinetic dissolution of carbonate minerals and plagioclase. An estimation of the mineral dissolution rates was obtained by fitting the arrival curves of the major ions.