The promising strategy of CO2 capture, utilization, and storage (CCUS) aims to reduce CO2 emissions and tackle the pressing problem of global warming. Previous studies have demonstrated the importance of changes in petrophysical and geomechanical characteristics in assessing target formations' capacity to sequester CO2. Permeability is one of these characteristics that is essential to the movement of CO2 inside rock formations and has a direct effect on how well CO2 is sequestered. Existing methods calculate permeability by using effective stress, but they have made unpractical assumptions that the effective stress coefficient could be stable or gradually increase after CO2 exposure. This study addresses this research gap by presenting experiment results on porosity, Poisson's ratio and permeability of rock samples obtained from middle Bakken subjected to CO2 submersion under controlled confining pressure and pore pressure. Experiments were conducted before and after the samples being submerged into supercritical CO2 for durations spanning from 20 to 60 days. The results demonstrated significant increases in porosity, with two samples showing increases by factors of 1.5 and 2.4, respectively. Additionally, permeability was observed to increase by factors ranging from 5 to 10 after submersion. This research establishes empirical relationships between time, confining pressure and pore pressure differential, and effective stress coefficient. These findings provide operators with a more accurate predictive tool for carbonate-rich samples in the middle Bakken formation during CO2 storage. By addressing the limitations of previous methods and offering new insights into the behavior of rock formations under CO2 exposure, this research enhances the evaluation of CO2 sequestration potential.
