Identifying the geological properties of ultramafic rocks for carbon storage potential

Project duration: July 2023–June 2024

Project lead

Team

Clive Foss, Giovanni Spampinato and Sarath Patabendigedara.

Opportunity

The optimal mechanism for storing atmospheric carbon over geologic timescales involves reacting carbon dioxide (CO₂) with rocks in-situ, known as mineral carbonation. Ultramafic rocks are the ideal candidate. The magnesium (Mg) silicate minerals they contain can react with CO₂ to form Mg carbonates at relatively low temperature and pressure (i.e. relatively shallow) conditions, and they are already mapped at a national scale.

Identifying appropriate mineral carbonation targets requires data on rock properties such as volume, depth, mineralogy and fluid permeability to determine reaction potential. This knowledge is fundamental to the economics of carbonation and provides rigid physical constraints to the feasibility of in-situ storage via carbonation, as well as potential implications for ex-situ mineral carbonation of mining tailings/waste.

Currently, such data typically doesn’t exist. However, our researchers have the tools to gather new information. Carbonation potential can be estimated by integrating information from these key data streams with 3D geological models to fill the existing knowledge gap. This project provides a cornerstone for building carbon locking technologies and will contribute valuable knowledge to the global push for carbon reduction and net-zero mining. It is a prerequisite for unlocking Australia’s potential to make in-situ mineral carbonation a reality. Part I of the project compiled relevant petrophysical data from ultramafic intrusions, Part II supplements that information with targeted studies on ideal ultramafic carbonation targets (e.g. high olivine and serpentine rocks) in eastern Australia.

Goal

Our goal is to assimilate knowledge from three main fields of geoscientific investigation to estimate carbonation potential in major ultramafic rock formations across Australia.

We’ll use petrophysical data to constrain geophysical modelling and provide estimates of rock volume and depth; geochemical analysis together with scanning electron microscopy (SEM) to provide estimates of Mg silicate content; and porosity/permeability measurements to provide estimates of fluid flow potential. The data we generate will allow us to replace the ‘best guesses’ in our models with facts.

Together, these research components will enable us to map high priority mineral carbonation targets across Australia. Based on experimental results and modelling, we’ll simulate their 3D architectures to determine potential reactive volumes, quantify their mineralogy (reaction potential) and porosity/permeability (flow potential) to estimate overall carbonation potential.

Barriers

To generate quality volume and depth estimations we need to constrain as many parameters as we can (i.e., prevent wide variation in other variables). We can do this by using multiple measurements for each parameter.

Some of the other challenges to modelling may include physical constraints such as availability of maps of the surface and subsurface extent of rocks, and complimentary information from remote sensing and other geophysical methods and models. Using the core team’s expertise, together with other world-leading CSIRO geoscientific knowledge and technologies, we’re confident we can meet these challenges to produce reliable national-scale baseline mapping of ultramafic mineral carbonation potential.

References

Cutts et al. (2021). Deducing mineralogy of serpentinized and carbonated ultramafic rocks using physical properties with implications for carbon sequestration and subduction zone dynamics.
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2021GC009989

Mitchinson et al. (2020). The Carbon Mineralization Potential of Ultramafic Rocks in British Columbia: A Preliminary Assessment. https://cdn.geosciencebc.com/pdf/CaMP_BC%20Prelim%20Report.pdf

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