Speaker
Description
CO2 storage in geological formations requires the understanding of multiphase multi-component flow over large reservoir-scale domains, where fully resolved three-dimensional simulations become computationally expensive and impractical for large-scale studies. Vertical-equilibrium (VE) modelling provides an efficient alternative for such systems. When vertical pressure equilibration is fast compared to lateral flow, the vertical structure of the flow is governed primarily by hydrostatic balance. The governing equations can then be integrated over the vertical direction, reducing the three-dimensional problem to a two-dimensional formulation based on vertically integrated variables while preserving mass conservation and buoyancy-driven dynamics. VE modelling has been widely developed and applied for CO2 storage in saline aquifers.
In this work, we develop a three-phase VE framework for gravity-dominated flow of CO2, methane, and brine in porous media, motivated by CO2 injection into depleted gas reservoirs. The model extends conventional two-phase VE formulations by introducing a third mobile phase and representing the system in terms of vertically segregated phase layers. CO2, methane, and brine are treated as separate phases within a black-oil-type formulation, enabling efficient simulation while aiming to preserve first-order displacement physics. Brine is treated as incompressible, while CO2 and methane are compressible. Pressure-dependent density and viscosity variations are derived from the Peng–Robinson equation of state and approximated using low-order analytical expansions, yielding mass-consistent vertically integrated properties without resolving fine-scale vertical structure.
Model behaviour is evaluated through comparison with high-resolution compositional simulations for a gravity-segregated anticline system. The VE model reproduces key porous-media flow characteristics observed in the fine-scale reference solutions, including buoyant rise of the injected phase, lateral migration under structural control, stable three-phase ordering, and evolution of gas–water contacts. Notably, plume extent, migration pathways, and final trapping locations are captured with good accuracy.
From a computational perspective, the VE approach reduces simulation time by more than two orders of magnitude compared to full compositional modelling, enabling rapid parameter studies, uncertainty analysis, and scenario screening that are impractical at fine scale. The results highlight the effectiveness of VE modelling as a physics-based upscaling strategy for gravity-dominated multiphase flow in porous media.
| References | Andersen, O., Gasda, S. E., & Nilsen, H. M. (2015). Vertically Averaged Equations with Variable Density for CO2 Flow in Porous Media. Transport in Porous Media, 107, 95–127. https://doi.org/10.1007/s11242-014-0427-z Ghanbari, S., Mackay, E. J., Heinemann, N., Alcalde, J., James, A., & Allen, M. J. (2020). Impact of CO2 mixing with trapped hydrocarbons on CO2 storage capacity and security: A case study from the Captain aquifer (North Sea). Applied Energy, 278. https://doi.org/10.1016/j.apenergy.2020.115634 Lie, K.-A. (2019). An Introduction to Reservoir Simulation Using MATLAB/GNU Octave: User Guide for the MATLAB Reservoir Simulation Toolbox (MRST). Cambridge University Press. https://doi.org/DOI: 10.1017/9781108591416 Moyner, O. (2024). JutulDarcy.jl - a Fully Differentiable High-Performance Reservoir Simulator based on Automatic Differentiation. ECMOR 2024, 2024(1), 1–37. https://doi.org/10.3997/2214-4609.202437111 Nordbotten, J., & Celia, M. (2011). Geological Storage of CO: Modeling Approaches for Large-Scale Simulation. Geological Storage of CO2: Modeling Approaches for Large-Scale Simulation, i–ix. https://doi.org/10.1002/9781118137086.fmatter |
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| Country | United Kingdom |
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