Injection of Geothermal CO2 and H2S Gases at the Nesjavellir Site: A Pre-injection Overview

Abstract

Orkuveita Reykjavíkur (OR) has been disposing CO2 and H2S waste gases emitted from the Hellisheidi Power Plant since 2014. The process involves capturing the gases through their dissolution in water at elevated pressure and injecting the gas-charged fluid directly into basaltic subsurface rocks without depressurization. In the subsurface the dissolved gases precipitate as minerals for their safe and long-term storage. The method has been developed within the CarbFix project and has been demonstrated to be safe, efficient and cost effective. Plans call for adopting this technology to capture and store the CO2 and H2S emitted from the Nesjavellir Power Plant, another geothermal plant owned and operated by OR. Preparation for a pilot injection of ~1000 tons of CO2 and ~600 tons of H2S annually is taking place as a part of the EU-funded GECO project. Here we present a general overview of the Nesjavellir injection site, including the subsurface stratigraphy, mineralogy, permeability and chemical composition of the target subsurface aquifer. Results indicate that the Nesjavellir geothermal field is a suitable host for successful carbon and sulphur mineralization due to its geological settings, available infrastructure, and the experience gained from the CarbFix injections at Hellisheidi (e.g. Gunnarsson et al., 2018; Snæbjörnsdóttir et al., 2017, Matter et al. 2016).