Quantifying stress-dependent permeability of ultramafic rocks
Project Leads
Professor David Healy and Professor Sandra Piazolo
Project Summary
There is an urgent need to tackle global warming and reduce CO2 and other greenhouse gases in the atmosphere. One suggested route forward is to sequester CO2 in the subsurface in solid form by injecting fluids into ultramafic rock formations, which produces chemical reactions in the fractures and precipitates carbonate minerals (e.g., Kelemen et al., 2008). For this to work, we need to understand the mechanical strength and hydraulic permeability of these rock types, as well as how these properties vary as fluid flow and reactions proceed. And yet, these data are poorly known. This project is a pilot study to explore the feasibility of using ultramafic rocks from the Lizard Complex, southwest England (and their offshore extension) as a potential CO2 storage site through coupled fracturing and reaction.
Aims & Objectives
In this project, the student will aim to deliver:
- Experimental exploration of the efficiency of in-situ carbonation by CO2 - ultramafic rock reaction
- Quantitative measurements of strength and stress-dependent permeability of ultramafic rocks; both unreacted and reacted
- Microstructural and microchemical mapping of carbonation reactions in microcrack networks;
- Estimate the potential of the Lizard complex for in-situ carbonation and CO2 sequestration
Methods & Training
- Field mapping and sampling of selected ultramafic sequences in Cornwall, SW England;
- Sample preparation, rock physics measurements at ambient conditions and thin section analysis of pristine/intact samples;
- Laboratory rock deformation experiments at elevated confining pressures and temperatures, with sufficient axial stress to generate microcrack networks to enhance fluid flow;
- Batch reaction experiments exploring in-situ carbonation in fractured samples;
- Microscale imaging and mapping of reaction sites in post-mortem samples from the two experimental suites.
Training will be provided in field structural geology (including systematic sampling), experimental rock mechanics, and microscale characterisation using the Scanning Electron Microscope (SEM). Experiments will be conducted in the Geosolutions Leeds Geomechanics Laboratory, the Experimental Petrology laboratory, and SEM analyses will be performed in the Bragg Centre.
Context, outcomes & Impact
This project will benefit from the wider Geosolutions Leeds project portfolio, including ongoing research into geothermal energy, subsurface storage of CO2 and H2, and critical minerals. Geosolutions Leeds is a core part of the University of Leeds Climate Plan, an ambitious £174M programme designed to achieve Net Zero on campus by 2030 and support decarbonisation of the city and wider region. The School of Earth & Environment (SEE) is a major international centre for Earth, Environmental and Sustainability Science that has wide-ranging and positive impacts, and much of our work is cross-cutting, tackling complex global challenges. This research will provide novel constraints on the potential for CO2 sequestration in ultramafic rocks, applicable to the UK and globally.