Abstract: Deep underground injection of carbon dioxide (CO2) into saline reservoir in China is in the stage of pilot project and field validation.The mechanical response of reservoir and fluid transportation induced by injection of supercritical CO2 are imperfect in theory and technology. In order to study the reservoir deformation and fluid transportation, the mass balance equations for both supercritical CO2 and saline are firstly presented based on two-phase flow model. The capillary pressure is introduced and served as the argument in the mass balance equations after some equation manipulations, with the help of relation between capillary pressure and saturation degree, which can facilitate consideration of the influence of fluid pressure on the reservoir formation. Secondly, a constitutive model is proposed to describe the mechanical behavior of dry rock of reservoir formation without fluid pressure, both the plastic deformation and damage mechanism can be considered. The coupling mechanism of fluid and reservoir formation is analyzed; the effective stress concept is used to consider the effect of fluid pressure on the reservoir formation, while the influence of reservoir deformation on fluid transportation is described by the variation of permeability of reservoir formation.

Key words: CO2 storage in saline aquifer, two-phase flow, elastoplastic, damage, effective stress, permeability, hydro-mechanical coupling