Date of Award
December 2024
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Petroleum Engineering
First Advisor
Kegang Ling
Abstract
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 sample 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 super-critical CO2 for durations spanning from 20 to 60 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. 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. What is more, existing methodologies employed by earlier experts to measure ultrasonic wave velocity and dynamic Young’s modulus (Edyn) of core samples extracted from the Middle Bakken member 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 (PSD), ultrasonic wave velocity, and Edyn 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 60 days. Furthermore, Edyn exhibited a discernible decrease ranging between 20 to 25 percent post-submersion. This research endeavor delved deeper into establishing empirical relationships between time, effective stress, and Edyn, 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. These findings provide operators with a more accurate predictive tool for carbonate-rich samples in the Middle Bakken member 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.
Recommended Citation
Ni, Ruichong, "Petrophysical And Geomechanical Alterations During Supercritical CO2 Submerge: Laboratory Testing On Samples From The Middle Bakken" (2024). Theses and Dissertations. 6553.
https://commons.und.edu/theses/6553