Speaker
Description
CO₂ injection into shale integrates resource exploration with carbon sequestration. Prior investigations have relied predominantly on crushed samples or CO₂-brine mixtures to study long-term geochemical interactions during soaking. Consequently, the essential mechanisms governing the evolution of flow capacity and microstructure across different injection methods remain poorly understood under realistic formation conditions. This study employs nuclear magnetic resonance (NMR) and multiple characterization techniques to investigate the microscopic mechanisms of flow evolution and sequestration efficacy across different CO₂ injection methods under actual formation conditions. Quantitative criteria are established to evaluate the contributions of distinct processes, and the influences of key factors and their interactions are systematically analyzed. Furthermore, a prediction model with multifactor coupling is constructed based on correlation analysis. The results show that CO₂ soaking under thermodynamic equilibrium transitions from physical to chemical control as pressure increases. At low pressure, limited particle migration rises blockage risks in micropores in zones above 0.06 mD. Elevated pressure enhances elastic energy, improving flow capacity by 100-200% in zones below 0.06 mD despite increased macropore blockage risks. Conversely, CO₂ flooding remains physically controlled by pressure gradients. Low pressure causes sharp flow decline due to particle blockage in narrow pore-throats, while increased pressure promotes high-speed CO₂ flow, reducing flow capacity by 7.79%-50.48% but increasing CO₂ gas column height by 1.67%-18.32%. For engineering practice, CO₂ flooding should be avoided in high-permeability, low-porosity formations under low pressure. Instead, during the middle-to-late stages, massive flooding in ankerite-rich zones is recommended to couple capillary and mineralization trapping.
| Country | China |
|---|---|
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