Reactive transport modeling of CO2 through cementitious materials under CO2 geological storage conditions

Abstract

A reactive transport model is proposed to simulate the reactivity of cement in contact with CO2-saturated brine and supercritical CO2 (scCO2). Dissolution and precipitation reactions for portlandite (CH) and calcite (CC¯) are described by mass action laws and threshold of ion activity products in order to account for complete dissolved minerals. A generalization of the mass action law is derived from thermodynamics and applied to calcium silicate hydrates (C-S-H) to take into account the continuous variation (decrease) of the C/S ratio during the dissolution reaction of C-S-H. We assume thermodynamical equilibrium for chemical processes. The porosity changes induced by the precipitation and dissolution reactions are also taken into account. Ion transport is described by using the Nernst-Planck equation as well as advection. Couplings between transport equations and chemical reactions are treated thanks to several mass balance equations written for each atom. We simulate by a finite volume method some experiments reported in the literature and compare our numerical results to these experimental observations.