CarbFix 2 siteBy Stuart Gilfillan, University of Edinburgh, School of GeoSciences

In late June, with the summer exam marking just about completed, Stuart Gilfillan, Gareth Johnson and Stuart Haszeldine from the Edinburgh Geoenergy and Scottish Carbon & Capture groups at the University of Edinburgh escaped the relative heat of Edinburgh to visit the somewhat cooler and definitely wetter CarbFix 2 site in Iceland.

Located at the Hellisheidi geothermal field, some 30 km outside of Reykjavik, the CarbFix 2 experiment was launched in 2014. The project is a scale up of the original and now well known 2011 CarbFix experiment, where around 175 tonnes of CO2 was dissolved into water and injected underground, via a single borehole, into a sequence of basaltic lava flows.

Basaltic lava is molten rock that is enriched in iron and magnesium. Two years following the CarbFix CO2 injection, geochemical tracer tests showed that that almost all (95%) of the CO2 injected had been trapped within new calcite minerals formed in the basaltic lavas. The experiment showed the viability of mineral trapping within reactive basaltic rocks as a permanent means to "lock away" the injected CO2.

At the scaled-up CarbFix 2 site, 10,000 tonnes of CO2 and 5000 tonnes of H2S are currently being injected per year into the CarbFix 2 site, which is run by Reykjavik Energy with the help of the University of Iceland. This consortium had invited the Edinburgh group out to the field site to see how the noble gas and stable isotope tracing techniques that the Edinburgh group have developed could be used to track the fate of the injected CO2 on the larger scale required in the new experiment.

The first day saw the group spend the morning getting an overview of the geothermal field, hosted by Sandra Snæbjörnsdóttir of Reykjavik Energy, and a having a productive afternoon meeting with Sigurdur Gislason’s group at the University of Iceland. Stuart Gilfillan and Gareth spent the following couple of days collecting water and gas samples from both producing wells and geothermal fumaroles (openings near volcanoes, though which hot sulphurous gases emerge) in the area. Stuart Haszeldine had a trip down memory lane by getting the opportunity to examine core samples collected from the original CarbFix experiment.

The group are following up this trip with laboratory analysis of the samples and are now looking to visit Iceland again in September where they will work with the CarbFix 2 team to develop funding proposals to continue to build on this initial pilot study.

This story was first published by the University of Edinburgh's School of GeoSciences.

Photo: Pétur Már Gíslason of Reykjavik Energy assisting with the sampling of gases from a geothermal fumarole located in the Hellisheidi field. (Credit: Stuart Gilfillan)

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