Flow-through reactor experiments on basalt-(sea)water-CO2 reactions at 90 °C and neutral pH. What happens to the basalt pore space under post-injection conditions?

D. Wolff-Boenisch*, I. M. Galeczka

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

16 Citations (Scopus)


Recent publications on the successful mineralisation of carbon dioxide in basalts in Iceland and Washington State, USA, have shown that mineral storage can be a serious alternative to more mainstream geologic carbon storage efforts to lock away permanently carbon dioxide. In this study we look at the pore solution chemistry and mineralogy of basaltic glass and crystalline basalt under post-injection conditions, i.e. after rise of the pH via matrix dissolution and the first phase of carbonate formation. Experimental findings indicate that further precipitation of carbonates under more alkaline conditions is highly dependent on the availability of divalent cations. If the pore water is deficient in divalent cations, smectites and/or zeolites will dominate the secondary mineralogy of the pore space, depending on the basalt matrix. At low carbonate alkalinity no additional secondary carbonates are expected to form meaning the remaining pore space is lost to secondary silicates, irrespective of the basalt matrix. At high carbonate alkalinity, some of this limited storage volume may additionally be occupied by dawsonite −if the Na concentration in the percolating groundwater (brine) is high. Using synthetic seawater as a proxy for the groundwater composition and thus furnishing considerable amounts of divalent cations to the carbonated solution, results in massive precipitation of calcite, magnesite, and other Ca/Mg-carbonates under already moderate carbonate alkalinity. More efficient use of the basaltic storage volume can thus be attained by promoting formation of secondary carbonates compared to the inevitable formation of secondary silicate phases at higher pH. This can be done by ensuring that the pore water does not become depleted in divalent cations, even after carbonate formation. Using seawater as carbonating fluid or injection of CO2 into the basaltic oceanic crust, where saline fluids percolate, can reach this goal. However, such an approach needs sophisticated reactive transport modelling to adjust CO2 injection rates in order to avoid too rapid carbonate deposition and clogging of the pore space too close to the injection well.

Original languageEnglish
Pages (from-to)176-190
Number of pages15
JournalInternational Journal of Greenhouse Gas Control
Publication statusPublished - Jan 2018

Bibliographical note

Funding Information:
We thank the AE Wildgust for handling this manuscript. Insightful comments and constructive reviews by Jonathan Icenhower and Helge Hellevang are also much appreciated and helped improve the quality of this paper. This study is part of the CarbFix project ( www.carbfix.com ) in Iceland and was funded by the European Union through the European Marie Curie network Delta-Min (Grant PITN-GA-2008-215360 ) and SP1-Cooperation (FP7-ENERGY-2011-1; Grant 283148 ), Reykjavik Energy, University of Iceland and RANNIS, Icelandic Fund for Research Equipment ; Grant 10/0293 and 121071-0061 ). The authors would like to thank all colleagues and collaborators from the Carbfix project, University of Iceland and Reykjavik Energy for fruitful discussions during the course of this study.

Publisher Copyright:
© 2017 Elsevier Ltd

Other keywords

  • Basaltic glass dissolution
  • Carbfix
  • Carbon mineralisation
  • Carbon storage
  • Mineral carbonation
  • Seawater-rock alteration
  • Zeolite smectite secondary formation


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