Effects of pore-scale heterogeneity on continuum-scale multiphase flow properties for subsurface carbon dioxide storage applications
File(s)
Author(s)
Darraj, Nihal
Type
Thesis
Abstract
Geological CO2 storage relies on multiple trapping mechanisms to ensure long-term subsurface containment. In depleted gas fields, structural trapping is the main mechanism and usually is sufficient, but in saline aquifers and settings where lateral migration poses risks, hence, additional trapping mechanisms are needed to slow and ultimately halt CO₂ migration. Among these, residual trapping is particularly important. It immobilises CO₂ after injection through pore-scale snap-off and capillary trapping behind regions of high capillary entry pressure. Although pore-scale residual trapping is well established in reservoir models, the influence of spatial heterogeneity in pore structure and capillary properties across larger length scales remains poorly constrained.
This thesis investigates how heterogeneity from pore to core scales controls multiphase flow and trapping under conditions relevant to geological CO₂ storage. A multiscale experimental approach combines steady-state coreflooding, X-ray computed tomography imaging, and pore-network analysis to directly observe displacement and trapping in heterogeneous sandstone and carbonate rocks under capillary-dominated flow regimes representative of saline aquifers and depleted hydrocarbon fields.
The first part examines sandstone samples from a Dutch offshore CO₂ storage site. Two samples taken only about 2 cm apart, from the same facies and with similar bulk porosity and permeability, display contrasting saturation profiles, displacement patterns, and residual trapping. Imaging shows that subtle differences in cementation and porosity distribution create capillary barriers and preferential flow paths in one sample, while the other behaves more uniformly.
The second and third parts show that, in Indiana limestone and Edwards Brown dolomite, heterogeneity interacts strongly with flow rate, connectivity, and capillary entry pressure, controlling saturation distribution, relative permeability, and trapping. Overall, the thesis demonstrates that routine core analysis alone cannot capture flow behaviour in heterogeneous rocks, and that capillary heterogeneity must be considered in more physically representative upscaling approaches for CO₂ storage.
This thesis investigates how heterogeneity from pore to core scales controls multiphase flow and trapping under conditions relevant to geological CO₂ storage. A multiscale experimental approach combines steady-state coreflooding, X-ray computed tomography imaging, and pore-network analysis to directly observe displacement and trapping in heterogeneous sandstone and carbonate rocks under capillary-dominated flow regimes representative of saline aquifers and depleted hydrocarbon fields.
The first part examines sandstone samples from a Dutch offshore CO₂ storage site. Two samples taken only about 2 cm apart, from the same facies and with similar bulk porosity and permeability, display contrasting saturation profiles, displacement patterns, and residual trapping. Imaging shows that subtle differences in cementation and porosity distribution create capillary barriers and preferential flow paths in one sample, while the other behaves more uniformly.
The second and third parts show that, in Indiana limestone and Edwards Brown dolomite, heterogeneity interacts strongly with flow rate, connectivity, and capillary entry pressure, controlling saturation distribution, relative permeability, and trapping. Overall, the thesis demonstrates that routine core analysis alone cannot capture flow behaviour in heterogeneous rocks, and that capillary heterogeneity must be considered in more physically representative upscaling approaches for CO₂ storage.
Version
Open Access
Date Issued
2026-02-06
Date Awarded
2026-04-01
Copyright Statement
Attribution-NonCommercial 4.0 International Licence (CC BY-NC)
License URL
Advisor
krevor, Samuel
Blunt, Martin
Pini, Ronny
Sponsor
Shell International Ltd
Shell
Publisher Department
Department of Earth Science & Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)