P06: Nanoscale Investigation of CO2-Induced Geomechanical Alterations in Shale Reservoirs

In the pursuit of carbon neutrality, carbon capture, utilization, and storage (CCUS) have gained widespread acceptance as effective strategies in addressing climate change. Despite ongoing efforts to improve this process, there exists a lack of understanding regarding the nanoscale mechanical alterations that storage reservoirs may undergo when exposed to supercritical CO2 (ScCO2) for extended periods. These nanoscale alterations can have a profound impact on the mechanical properties of the reservoir. Understanding the long-term impacts of supercritical CO2 (ScCO2) exposure on unconventional shale reservoirs is essential due to their use in CO2-enhanced oil recovery (CO2-EOR) and CO2 storage. This study aims to investigate the continuous nanoscale mechanical changes in Middle Bakken shale when subjected to long-term ScCO2 exposure. Through comprehensive analysis of Middle Bakken shale samples before and after ScCO2 treatments, the study employs nanoindentation testing to examine the long-term nano-mechanical alterations in the depleted shale reservoir as a result of ScCO2 exposure, focusing on the variations in its properties. The results demonstrate that prolonged exposure to ScCO2 weakens the nanoscale mechanical integrity of Middle Bakken shale. As the duration of saturation increases, the interactions between the sample and CO2 intensify, resulting in a steeper slope value compared to the initial state. This leads to an increased ductility of the shale. This study provides valuable insights for the effective design and implementation of CCUS projects in shale reservoirs, particularly in the Middle Bakken formation. Understanding these variations and incorporating them into project planning is essential to prevent potential CO2 leaks and environmental hazards associated with inadequate comprehension of these alterations.