Effect of CO₂ phase on pore geometry of saline reservoir rock

Abstract

The phase of CO₂ present in a saline reservoir influences the change of the pore geometry properties of reservoir rocks and consequently the transport and storage integrity of the reservoir. In this study, digital rock physics was used to evaluate pore geometry properties of rocks saturated with the different phaseCO₂-brine under reservoir conditions. The changes in the pore geometry properties due to the different phaseCO₂-brine-rock interaction were quantified. In addition to compression, CO₂-brine-rock interaction caused a further reduction in porosity by precipitation. Compared to the dry sample, the porosity of the gaseous CO₂-br sample was reduced the most, and was lower by 15% after saturation and compression. There was reduction in the pre-compression porosity after compression for all the samples, however, the reduction was highest in the gaseous CO₂-br-saturated sample (13%). The flatness of pore surfaces was reduced, and pores became less rounded after compression, especially in supercritical CO₂-br-saturated rock. The results from this research provide a valuable input to guide a robust simulation of CO₂ storage in reservoir rocks where different phases of CO₂ could be present.