A constitutive model accounting for CO2 inducing chemo-mechanical damage.

DIEGO MANZANAL; JEAN MICHEL PEREIRA

Sao Paulo

Congreso; 10th WORLD CONGRESS ON COMPUTATIONAL MECHANICS (WCCM 2012); 2012

Universidade de São Paulo

Sequestration of carbon dioxide (CO2) in deep geological reservoir has issued as one of the most promising technologies to reduce the emissions of greenhouse gases to atmosphere. The interface between the cement sheath surrounding the wellbore used for injection of CO2 and the caprock is seen as a potential leakage path. Chemo-mechanical interactions between the cement and low-permebility caprock formation could indeed alter the hydromechanical properties of this interface and provide a path for leaking CO2 towards upper formations. In the present study a chemo-mechanical damage model for caprock-wellbore interface saturated with aqueous supercritical CO2 is presented. The major chemical reactions on the rock-cement interface are presented. In particular, the effect of cement carbonation and carbonates precipitation is taken into account. The chemical processes involved in CO2 injection in deep cemented wells could induce microcracking due to growth of calcite crystal. Chemical damage processes induce irreversible strain related to anisotropic damage tensor. This chemo-mechanical model is based on an anisotropic continuum damage mechanics coupling crystal growth theory in confined condition. The coupling crystal growth kinetic and mechanical responses are evaluated by chemical and mechanical path. Dissolution/precipitation of minerals on interface induce variation of the stress and strain state and could be an important weakening process leading to failure and CO2 migration.