Effects of CO2 on mechanical variability and constitutive behavior of the Lower Tuscaloosa Formation, Cranfield Injection Site, USA

Chemical environment affected the mechanical response of all three lithofacies, which experience initial plastic yielding at stresses far below estimated in situ stress. Measured elastic moduli degradation defines a secondary yield surface coinciding with in situ stress for Facies B and C. Facies A shows measurable volumetric creep strain and a failure envelope below estimates of in situ stress, linked to damage of chlorite cements by acidic pore solutions. The substantial weakening of a particular lithofacies by CO2 demonstrates a possible chemical-mechanical coupling during injection at Cranfield with implications for CO2 injection, reservoir permeability stimulation, and enhanced oil recovery.