The escalating concentration of atmospheric carbon dioxide (CO₂) is a primary driver of global climate change, necessitating the development an‎d deployment of effective mitigation strategies. Carbon Capture an‎d Storage (CCS), particularly in deep saline aquifers, represents a pivotal technology for sequestering large volumes of industrial CO₂ emissions. However, the efficiency an‎d long-term security of geological storage are governed by complex multiphase flow an‎d trapping mechanisms, which require robust predictive tools for optimization. This research employs advanced numerical simulation using the Computer Modelling Groupʹs GEM compositional simulator (CMG) to eva‎luate an‎d optimize CO₂ sequestration in a representative deep saline aquifer. A systematic methodology was developed, involving the construction of a 3D homogeneous model, calibration of the Peng-Robinson Equation of State for accurate CO₂-brine phase behavior, an‎d definition of rock-fluid interactions. The study simulated 10 years of CO₂ injection followed by a long-term monitoring period to assess the dynamic evolution of trapping mechanisms: structural, residual, an‎d solubility trapping. The results unequivocally demonstrate the dominance of gravity segregation, leading to a characteristic override of the CO₂ plume, which migrates laterally beneath the caprock. A significant pressure "bulb" develops around the injection well, highlighting the critical importance of pressure management for geomechanical integrity. The analysis of dynamic properties, particularly the evolution of gas relative permeability, provides direct evidence of the gradual activation of residual trapping, which immobilizes a substantial portion of the CO₂ plume over time, thereby enhancing storage security. Solubility trapping initiates immediately, marking the beginning of long-term permanent stabilization. In conclusion, this thesis validates a robust simulation workflow using CMG-GEM an‎d demonstrates the multi-mechanistic nature of CO₂ sequestration, where structural, residual, an‎d solubility trapping act in sequence to ensure safe an‎d permanent storage. The findings provide critical insights for designing injection strategies an‎d risk assessment protocols, contributing to the practical deployment of CCS technology in the global effort to combat climate change.

محسن محمدي

حميدرضا شاه وردي , روح اله هاشمي