title: A Parallel Thermal Simulator for Large-Scale Numerical Simulations of Geological Carbon Dioxide Utilization and Storage
Creators: name: Di, Chaojie
Publisher: name: Schulich School of Engineering
Year: 2025
Subjects: subject: Numerical reservoir simulations
subject: CO2 utilization and storage
subject: Geothermal extraction
subject: Fluid phase equilibrium
subject: Rock wettability
subject: Engineering--Environmental
subject: Energy
subject: Engineering--Petroleum

description: The intensifying global climate crisis, driven by rising greenhouse gas emissions, has underscored the urgent need for effective carbon management strategies. Among these, Carbon Capture, Utilization, and Storage (CCUS) has emerged as a critical technology for achieving carbon neutrality by mitigating anthropogenic CO₂ emissions. The success of these approaches depends on an in-depth understanding of subsurface processes, where numerical reservoir simulation plays a pivotal role in predicting fluid flow in formations, evaluating storage efficiency, and optimizing operational strategies for large-scale deployment. However, current commercial software and academic codes have limitations in simulating the above processes, with many aspects requiring further improvement. To address these challenges, this research focuses on the development of a parallel reservoir simulator tailored for geological CO₂ utilization and sequestration (GCUS). This simulator is an extension and improvement of a compositional reservoir simulator developed by our research group, with parallelization calculation implemented through our Parallel Reservoir Simulation Infrastructure (PRSI). This simulator integrates advanced fluid phase equilibrium and rock wettability models to enhance the accuracy of multiphase flow simulations in geological formations. This study is structured into several key areas. It begins with the development of a fluid phase equilibrium model and a rock wettability modeling framework tailored for CO₂-related fluid systems. These fundamental models are then applied to investigate different CO₂ storage and utilization scenarios, including CO₂ sequestration in deep saline aquifers, where trapping mechanisms and storage efficiency under various geological conditions are evaluated. The research further extends the simulations to CO₂-plume geothermal systems, analyzing the thermal and hydrodynamic behavior of CO₂ for geothermal energy extraction. Additionally, it explores CO₂-enhanced oil recovery, assessing the impact of CO₂ injection on reservoir performance and hydrocarbon production. The findings of this study highlight the influence of gas impurities on carbon sequestration, demonstrating that small amounts of SO₂ have minimal impact on CO₂ solubility but enhance stable storage by increasing the proportion of dissolved and immobile CO₂, while O₂ and H₂ reduce storage stability and increase injection pressure requirements when their concentration exceeds 10%. A novel Adaptive Saturated Composition (ASC) algorithm was developed to improve computational efficiency by selectively bypassing unnecessary stability analyses while maintaining high accuracy, significantly reducing the computational cost of phase equilibrium calculations. Simulations of CO₂ Plume Geothermal (CPG) systems confirmed that CO₂ serves as an effective heat transfer medium, sustaining substantial enthalpy and production rates during operation; however, post-operation thermal expansion increased reservoir pressure, leading to CO₂ leakage exacerbated by temperature-induced wettability alteration. Additionally, a phase labeling method was introduced to enhance the stability and accuracy of CO₂-enhanced oil recovery (EOR) simulations, preventing arbitrary phase transitions and improving numerical robustness. These advancements contribute to a more reliable and computationally efficient framework for modeling geological CO₂ storage and utilization, providing insights into optimizing storage efficiency, mitigating leakage risks, and ensuring the long-term security of CCUS applications.