Pore-scale Simulations of Multiphase Flow for CO2 Migration Through Saline Aquifers in the Capillary- Dominated Regime

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Larson, Richard
Bakhshian, Sahar
Hosseini, Seyyed A.

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Carbon capture and storage intends to inject anthropogenic carbon dioxide from large point sources into the geologic formations for emissions mitigation. In geological carbon sequestration, it is critical to understand the behavior of carbon dioxide as it displaces subsurface, resident fluids during storage to assure its safety and permanence. The multiphase nature of carbon dioxide displacing saline water over long-term periods of post-injection relies heavily on the buoyancy forces arising from the density contrast between CO2 and saline water and the capillary forces controlled by the pore geometry at the pore scale. The competition of those governing forces controls the field-scale migration and confinement of CO2 in reservoir formations. In this study, we use high fidelity pore-scale simulations of multiphase flow to investigate this phenomenon in porous geometries representative of sedimentary rock formations. A computational fluid dynamic technique known as the volume of fluid method is taken to model the buoyancy-driven flow of CO2 in subsurface reservoirs. There are many computational burdens in these simulations. High-resolution meshes with a high number of grid cells are required to capture the complexity of the pore morphology leading to a high computational burden when considering the number of necessary simulated timesteps. Even reducing the domain size of the models to an effective 2-dimensional (2-d) structure with an area less than 1 cm2, nearly prohibitive computational time is needed. Furthermore, to replicate the capillary dominated flow, low velocity values are needed. However, the slower the flowrate, the more an interfacial issue known as spurious currents occurs, leading to numerical instabilities. To handle this numerical issue, simulations with smaller timesteps are required, but in tandem with the slow velocities, computational expense is further compounded. The usage of TACC’s parallel processing resources along with optimization techniques facilitates solutions and results that inform us about the fundamental mechanics of this flow.



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