Characterisation of sub-resolution porosity in sedimentary rocks by x-ray computed tomography
File(s)
Author(s)
Roa Pérez, Juan Carlos
Type
Thesis
Abstract
Accurate porosity characterisation is critical for understanding fluid flow in geological porous media, yet existing methods face significant limitations in capturing multi-scale pore systems in sedimentary rocks. This thesis develops and validates a novel dual-resolution X-ray computed tomography (CT) methodology that integrates medical CT and micro CT imaging to provide three-dimensional porosity quantification across multiple length scales. The dual-resolution approach addresses the fundamental trade-off between spatial resolution and field of view in conventional CT methods. Medical CT provides large-scale effective porosity maps with complete sample coverage, while micro CT resolves individual pore structures at microscale for the same domain. Integration of these complementary datasets enables quantification of effective, resolved, and unresolved porosity components within a unified framework, providing important insight into hierarchical pore system organisation. A key innovation involves using radio-opaque gases, specifically krypton, as saturating fluids for differential imaging. This advancement extends applicability to low permeability samples where conventional liquid saturants cannot penetrate adequately, overcoming a major limitation in tight rock characterisation. The methodology was validated on four representative sedimentary rocks: Bentheimer sandstone, Ketton limestone, Nugget sandstone, and Silurian dolomite, encompassing both simple and complex porosity systems. Validation against established techniques including helium pycnometry, mercury intrusion, and Archimedes methods demonstrates excellent agreement, with porosity values typically within 2-3% of reference measurements. The method successfully generates detailed 3D porosity maps revealing spatial heterogeneity and connectivity patterns. The approach enables enhanced parametrization through sub-resolution porosity mapping in numerical modelling applications, showing important differences in transport behaviours when heterogeneous sub-resolution porosity is applied, representing significant advancement over traditional homogenised approaches. This work addresses critical needs in reservoir characterisation, carbon sequestration, and geothermal applications. The dual resolution methodology provides enhanced tools for characterising complex porous media and establishes new opportunities for porosity quantification in digital rock physics.
Version
Open Access
Date Issued
2025-09-03
Date Awarded
01/01/2026
License URL
Advisor
Pini, Ronny
Sponsor
Engineering and Physical Sciences Research Council
Grant Number
EP/V038044/1
Publisher Department
Department of Chemical Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)