How Does Fault-Related Alteration of Basalt Affect the Potential for Geological Carbon Sequestration in Basalt Formations?

6 Pages Posted: 31 Jul 2020

See all articles by Montserrat Recasens

Montserrat Recasens

Heriot-Watt University - Research Centre for Carbon Solutions (RCCS)

Kitson Lim

Heriot-Watt University - Research Centre for Carbon Solutions (RCCS)

M. Mercedes Maroto-Valer

Heriot-Watt University - Research Centre for Carbon Solutions (RCCS)

Rachael Ellen

BGS Scotland

Susana Garcia

Heriot-Watt University

Date Written: October 21, 2018

Abstract

Basalt is an increasingly attractive target for CO2 storage via mineral trapping, due to its abundance of reactive divalent cations such as Ca2+, Mg2+ and Fe2+. The majority of previous studies into the potential for CO2 storage in basalts have used fresh basalt samples. However, it has generally been beyond of the scope of existing studies to look at the effects of faulted and altered basalt at depth, which might have an effect on CO2 storage estimates, especially in geologically older basalt volumes. In this study, two mugearite basalt samples were collected to assess potential for CO2 reactions: a fresh basalt, and its faulted equivalent (altered by fault-related fluids). The faulted equivalent contains less olivine and clinopyroxene compared with its fresh counterpart, due to fluids altering them to clay minerals during and after faulting. Two batch experiments were conducted in synthetic aquifer water (brine) at 50C and PCO2= 130 bar with the aim of investigating potential change in basalt composition and/or concentration of the brine caused by chemical reactions between the basalt rocks and CO2-saturated brine. After 30 days of reaction, Fe2+, Ca2+, Si4- , Al3+ and Mg2+ were leached from the fresh basalt sample showing a potential dissolution of reactive minerals such as olivine and clinopyroxene minerals from the original sample. In contrast, no changes of Fe2+ concentration were observed in experiments performed for faulted basalt. The increase of Fe2+, Ca2+, Si4- , Al3+ and Mg2+ concentration was higher in the fresh basalt experiment compared with the faulted basalt sample. This is most likely due to less reactive minerals available within the faulted sample, such as olivine and pyroxene, having been partially or completely replaced by clay minerals following faulting. Our study therefore finds that faulted and altered basalt is in general less reactive to CO2 than fresh basalt, and this may have implications for the storage of CO2 via mineral trapping in basalts in geologically old and faulted basalt volumes. If basalt volumes targeted for CO2 storage in the future contain geological faults, bulk estimates for mineral trapping of CO2 should take into account the possibility of a difference in reaction rates across the rock volume, and complete additional lab studies to quantify any difference.

Keywords: Trapping mechanisms, GHGT-14, mugearite basalt; faulted basalt volumes; mineral trapping; CO2 storage

Suggested Citation

Recasens, Montserrat and Lim, Kitson and Maroto-Valer, M. Mercedes and Ellen, Rachael and Garcia, Susana, How Does Fault-Related Alteration of Basalt Affect the Potential for Geological Carbon Sequestration in Basalt Formations? (October 21, 2018). 14th Greenhouse Gas Control Technologies Conference Melbourne 21-26 October 2018 (GHGT-14) , Available at SSRN: https://ssrn.com/abstract=3366105 or http://dx.doi.org/10.2139/ssrn.3366105

Montserrat Recasens

Heriot-Watt University - Research Centre for Carbon Solutions (RCCS)

Edinburgh, EH14 4AS
United Kingdom

Kitson Lim

Heriot-Watt University - Research Centre for Carbon Solutions (RCCS)

Edinburgh, EH14 4AS
United Kingdom

M. Mercedes Maroto-Valer

Heriot-Watt University - Research Centre for Carbon Solutions (RCCS)

Edinburgh, EH14 4AS
United Kingdom

Rachael Ellen

BGS Scotland

The Lyell Centre
Research Avenue South
Edinburgh, EH14 4AP
United Kingdom

Susana Garcia (Contact Author)

Heriot-Watt University ( email )

Riccarton
Edinburgh EH14 4AS, EH14 1AS
United Kingdom

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