Author Identifier
Seyi Philemon Akanji: http://orcid.org/0000-0002-3224-9172
Date of Award
2025
Document Type
Thesis
Publisher
Edith Cowan University
Degree Name
Doctor of Philosophy
School
School of Engineering
First Supervisor
Stefan Iglauer
Second Supervisor
Lionel Esteban
Third Supervisor
Alireza Keshavarz
Fourth Supervisor
Ausama Giwelli
Abstract
Geological carbon dioxide (CO2) sequestration through in-situ mineralization in basaltic formations offers a promising and secure pathway for long-term carbon storage. This study evaluates the potential of basaltic rocks from Western Australia as viable candidates for mineral-based CO2 sequestration, integrating a comprehensive literature review, laboratory experiments, and coupled geochemical geomechanical analyses. Conventional geological storage involves injecting CO2 – either gaseous or supercritical – into porous reservoirs, relying on structural traps, capillary forces, and dissolution in groundwater to ensure containment. In contrast, mineralization-based storage injects CO2-saturated water into mafic rocks such as basalts, inducing chemical reactions that convert CO2 into stable carbonate minerals, thereby minimizing the risk of atmospheric release. Results indicate that dissolution–precipitation reactions significantly alter basalt microstructure, governed by sufficient fluid residence time within pore spaces, reactive surface area (both total and mineral-specific), and permeability and porosity that allow efficient CO2-saturated water injection with minimal energy input. While dissolution enhances pore connectivity and injectivity, secondary carbonate precipitation can occlude flow paths; however, fracture development under reservoir pressure–temperature gradients may counterbalance these effects. Field-scale evidence, such as from the CarbFix project, demonstrates that continuous dissolved-CO2 injection promotes near-well dissolution while displacing carbonate precipitation farther from the injection zone, reducing clogging risks. Overall, the findings highlight basaltic formations as safe, scalable, and durable reservoirs for permanent CO2 storage, though further work is required to quantify pore-scale processes and optimize injection strategies.
The success of CO2 storage in basaltic formations is also critically influenced by interfacial parameters, particularly the wettability of the rock-water-CO2 system, which governs fluid distribution, transport, storage capacity, and containment security. Accordingly, this study investigated the wettability of several altered Western Australian basalt samples with similar geochemistry, porosity, and interconnectivity, using synthetic formational water containing ions leached from the rock samples. Under realistic geostorage conditions (10 – 80 bar, 50 °C), most samples exhibited intermediate-wet behaviour, while increasing pressure to 100 bar at 50 °C shifted most samples toward weakly CO2-wet behaviour, with one sample retaining its intermediate-wet state. These findings underscore the potential of altered Western Australian basalts for mineral-based CO2 storage and highlight the influence of pressure on interfacial dynamics.
To further examine this potential, microstructural transformations were explored in both intact and mechanically fractured basalt samples across diverse compositional profiles. Given the low porosity and permeability of these tight basalts, controlled fracturing was employed – via microwave irradiation, thermal treatment, and cryogenic (liquid nitrogen) techniques – to enhance fluid accessibility and expose reactive mineral surfaces. Rock-fluid interactions were monitored in static batch reactors under simulated reservoir conditions (50 bar, 60 °C) over 154 days, with periodic pressurization depressurization cycles to accelerate dissolution and mineralization. Comprehensive characterization, including X-ray CT and SEM-TIMA imaging, porosity–permeability measurements, ultrasonic velocity analysis, and geochemical assays (XRD, XRF, and fluid composition), revealed heterogeneous rock responses. Some samples exhibited increased porosity and permeability due to dissolution of primary and secondary minerals, while others showed reductions from pore compaction. Secondary carbonate, predominantly calcite (28.44 wt%), observed in intact sample GSWA 225880, retrieved from the deepest depth (1986.10 m to 1986.125 m), highlighting the influence of mineralogy and alteration history (39 wt% plagioclase, 2 wt% pyroxene, 6wt% pre-existing calcite and 34 wt% chlorite) on carbonation potential. Other samples displayed net dissolution without carbonate precipitation. Elastic property measurements indicated an overall reduction in stiffness, though carbonate formation and compaction locally mitigated mechanical weakening.
Collectively, these findings elucidate the complex interplay among fracture enhancement, mineral dissolution, and carbonate precipitation in governing CO2 mineralization and long-term reservoir integrity. They also provide important insights into the mechanical stability and chemical reactivity of Western Australia’s basaltic formations as secure and durable CO2 storage reservoirs.
Access Note
Access to this thesis is embargoed until 20th December 2028
DOI
10.25958/wnwp-ct98
Recommended Citation
Akanji, S. (2025). Potential of volcanic rocks for underground gas storage in Western Australia. Edith Cowan University. https://doi.org/10.25958/wnwp-ct98