Impact of Rock–ScCO₂ Interaction on Shale Features and Its Implication in CO₂ Geological Storage and Fracturing: Review and Perspectives

Abstract

CO2 geological sequestration (CGS) is one of the most realistic and practical technology to safeguard large-scale carbon reduction to maintain carbon neutrality and capping carbon goals, especially with greenhouse gas emissions expected to reach record highs these last years. The qualities of self-storage and self-generation are shared by coalbed methane and shale gas, making them both attractive candidates for geological CO2 sequestration. When a significant amount of CO2 is injected into shale gas reservoirs, a number of geomechanical, petrophysical, and geochemical problems could arise and cause leakage. Thus, a comprehensive understanding of how the contact between CO2 and the anisotropic rocks such as organic-rich shale gas reservoir influences the initiation and propagation of cracks requires thorough investigation. This paper provides an overview of earlier research on the impacts of ScCO2–shale rock interaction with a focus on its involvement in carbon capture and storage (CCS), spread, and behavior of fractures. The findings showed that CO2-induced invasion would most likely result in a high percentage of quartz and a low content of carbonate and clay minerals. Compared to clay, carbonate reacts more readily to CO2. Shale gas reservoir can be made softer, less brittle, more resilient, and more plastic by injecting CO2. Supercritical CO2 results in a larger reduction of Young’s modulus and uniaxial compression stress. Lastly, other issues are raised, including how the bedding plane affects the failure pattern, crack growth, and hydraulic fracturing failure strength. The findings indicate that the initiation and spread of hydraulic fractures in organic-rich shale are influenced by the interplay between stress state and rock fabric. This broadens our understanding of the basic behavior of fractures and could help develop effective hydraulic fracture approaches for real-world use. We draw the conclusion from this review that the efficiency of CO2 capture and storage is significantly influenced by the shale/CO2 interaction. However, because shales are heterogeneous, more complex simulation tools and experiments are required to monitor the multifield coupling action in order to properly know and uncover the process of fracture initiation and growth in shale rock and determine how the mineralogy of distinct shales may impact the long-term capacity to store CO2.