Improving Precision in Assessments for CO2 Geological Storage: Investigating the Influence of Pore Pressure on Rock Properties

Carbon dioxide (CO2) capture and storage constitute pivotal strategies in mitigating emissions stemming from the combustion of fossil fuels. Prior investigations have underscored the significance of various petrophysical and geomechanical properties in determining the CO2 storage potential of rock formations, primarily through conventional laboratory testing methods. However, existing methodologies employed by earlier experts to measure ultrasonic wave velocity and dynamic Young’s modulus (E dyn) of core samples extracted from the Middle Bakken formation during CO2 submersion have often overlooked the critical influence of pore pressure, consequently falling short of accurately replicating in situ conditions. Achieving a faithful replication of reservoir conditions within laboratory settings is imperative for the thorough assessment of the reliability and efficacy of CO2 storage systems. This paper endeavors to address crucial gaps by focusing on the meticulous quantification of pore size distribution, ultrasonic wave velocity, and E dyn of core samples subjected to CO2 submersion under appropriate pressure conditions. Experimental assessments were conducted both prior to and after subjecting the core samples to CO2 submersion for durations spanning from 10 to 50 days. The findings gleaned from this study reveal compelling insights, demonstrating that the porosity of the samples exhibited an expansion to 1.5 times its original value prior to submersion. Furthermore, E dyn exhibited a discernible decrease ranging between 20 and 25% postsubmersion. This research endeavor delved deeper into establishing empirical relationships between time, effective stress, and E dyn, alongside ultrasonic wave velocities. These relationships are crucial for gaining a nuanced understanding of the dynamic interplay between these key variables, thereby elucidating the intricate mechanisms governing the behavior of core samples during CO2 submersion. This study contributes valuable insights into the underlying dynamics of CO2 storage systems, paving the way for enhanced predictive modeling and informed decision-making in the realm of carbon capture and geological storage (CCS) initiatives.