The geology and water chemistry of the Hellisheidi, SW-Iceland carbon storage site

Abstract

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Differential alteration of basaltic lava flows and hyaloclastites in Icelandic hydrothermal systems

“…The thickness of individual layers is variable and irregular (Watton et al 2013), varying between a few meters and a few hundred meters (Alfredsson et al 2013).…”

“…They are present in many volcanic systems all around the world (Zierenberg et al 1995;Altaner et al 2003;Honnorez 2003;Claridge and Campbell 2008;Moore et al 2012;Barfod and Fitton 2014;Kanayama et al 2014;Motelib et al 2014) and also in Mars (Hovius et al 2008;Scanlon et al 2014). Hyaloclastites exhibit high porosity up to 60 % (Franzson et al 2010;Alfredsson et al 2013); relatively high initial permeability from 10 −13 to 10 −12 m 2 (Jarosch et al 2008); and a wide range of granulometry:…”

Frictional Instabilities and Carbonation of Basalts Triggered by Injection of Pressurized H2O‐ and CO2‐ Rich Fluids

“…Notably, to approach the CarbFix reservoir working conditions, several tests were performed by applying σ n  = 15 MPa and an initial Pf  = 2.5 MPa at room temperature ( T  ~ 20–25°C; Alfredsson et al, 2013). The experimental procedure consisted of the following steps: first we inserted the sample inside the pressure vessel and pumped the fluid to 0.1 MPa.…”

“…However, the amount of dissolved CO 2 at operative depths typical for carbon sequestration into basaltic aquifers (Alfredsson et al, 2013) is in the ratio 30–70 g CO 2 per kg H 2 O (Choi & Nešić, 2011). Consequently, the large amounts of water to be injected during subsurface CO 2 storage efforts may trigger earthquakes in response to pore fluid overpressures in the vicinity of preexisting faults (Zoback & Gorelick, 2012).…”

“…In fact, to date, this is the first storage site in which CO 2 is dissolved in H 2 O before being injected in a basalt‐built reservoir. The reservoir is located in a low‐temperature geothermal area at ∼500 m depth, corresponding to a lithostatic pressure of about 15 MPa, and at ∼25°C ambient temperature (Alfredsson et al, 2013). Our results that could apply to other voluminous basaltic occurrences (e.g., continental flood basalts sequences) show that fault instability nucleation occurs regardless of the state of alteration of basalts and chemical composition of injection fluids.…”