Numerical Simulation of CO2 Storage Behavior: Investigation of Physical and Geochemical Trapping in Heterogeneous Underground Structures

Large-scale carbon capture and storage (CCS) stands a crucial role in achieving net-zero emissions by 2050. To successfully deploy the geological CO₂ storage, it is essential to consider heterogeneities of storage reservoirs and surrounding strata. The variation of porosity, permeability, relative permeability, and capillary pressure have a significant influence on storage capacity, potential leakage, CO₂ plume migration, and risk assessment. Besides, underground aqueous CO₂ can convert to minerals or form insoluble ionic species if reacting with specific ions or solid minerals. These processes, known as geochemical trapping, is considered as the most permanent form of storage.

In this work, we utilize the well-known multiphase flow software TOUGH3 as well as reactive-transport software TOUGHREACT with module ECO2N, to simulate the behavior of CO₂ injected into the 2D large-scale models comprising aquifer, seal, and reservoir layers with homogeneous distributions.  A series of sensitivity studies on porosity-permeability relations, different pairs of relative permeabilities and different heterogeneous distributions generated from a geostatistical software SGeMS will be conducted in this work to investigate their impacts on CO₂ plume migration and pressure evolutions.  In addition, capillary trapping mechanisms are also simulated based on sensitivity studies on different capillary pressure curves. Finally, brine with different concentration species is considered to simulate the geochemical trapping.

This research aims to achieve the following objectives: 1. Examine the impact of uncertainties of petrophysical properties and heterogeneities. 2. Analyze preliminary results of predicted pressure buildup and saturation distribution in the heterogeneous models. 3. Evaluate the possible storage capacity of both physical and geochemical trapping.