Thesis
Exploiting induced carbonate precipitation to improve reservoir storage integrity and geothermal system efficiency
- Creator
- Rights statement
- Awarding institution
- University of Strathclyde
- Date of award
- 2026
- Thesis identifier
- T18074
- Person Identifier (Local)
- 202073516
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- Induced carbonate precipitation (ICP), through microbial (MICP) and enzyme-induced (EICP) pathways, offers a sustainable means of reinforcing porous media, tuning permeability, and enhancing thermal performance across soils, engineered backfills, and subsurface formations for applications in carbon storage, geothermal energy, and construction. Yet its wider deployment is prevented by limited understanding of how pore-scale precipitation processes shape bulk material behaviour, particularly when relying on crude, low-cost enzyme extracts essential for scalable treatments. This thesis aims to show how pore-scale precipitation processes govern material performance and how they can be directed to achieve specific outcomes. Time-lapse X-ray computed tomography and flow modelling revealed that density driven mixing controls where and when CaCO3 forms, with precipitation concentrated in regions of high enzyme availability. This highlights that density driven flow, such as injecting cementing solution above enzyme solution in deep formations, can be exploited to deliberately control where precipitation occurs. By varying enzyme source, organic additives, flow regimes, and pH, new levers were identified for modulating reaction kinetics and lag periods. Crude soybean urease generates extended protein-mediated lag phases that allow cementing and enzyme solutions to be mixed ex situ prior to injection. This strategy produced more uniform precipitation, even across fine layers (<100 μm) that were otherwise inaccessible to bacterial cells in MICP and enabled extended treatments of up to 25 cycles due to sustained uniform precipitation. As an alternative, pulsed-flow injection was shown through flow modelling to enhance pore-scale mixing between cementing and enzyme solutions, offering another pathway for improved treatment uniformity. Linking these optimised treatments to bulk properties showed that repeated EICP injections could achieve unconfined compressive strengths up to 17.9 MPa while increasing thermal conductivity by ~600% and preserving hydraulic conductivity, a tuneable balance between reinforcement and flow. XCT demonstrated that strength gains were associated with crystal bridging at grain contacts, which also facilitated efficient heat transfer. Functional optimisation using conductive and phase-change additives established ICP treated porous media as multifunctional composites. Expanded graphite formed conductive networks that delivered anisotropic heat conduction, while paraffin-infused graphite enabled latent heat storage. Additives thus delivered equal or greater thermal enhancements with far fewer treatment cycles than enzyme-only treatments. Overall, this work demonstrates that precipitation uniformity and mixing dynamics are central to ICP performance. By connecting pore-scale mechanisms to engineering outcomes and extending ICP to multifunctional applications, this thesis advances both the mechanistic understanding and the practical potential of biomineralisation, moving it significantly closer to deployment in CO2 sequestration, geothermal energy, and sustainable construction.
- Advisor / supervisor
- Minto, James
- Dobson, Katherine
- Resource Type
- DOI
Relations
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PDF of thesis T18074 | 2026-06-23 | Public | Download |