GECO: Geological Properties, Permeability and Porosity of the Nesjavellir High Temperature Area in Relation to the Re-injection of Geothermal CO2 and H2S Gases

Abstract

GECO (Geothermal Emission Control) is an international research project that started in 2018, funded by the EU through the H2020. One of the goals of the GECO project is to prepare for re-injection of geothermal CO2 and H2S from the Nesjavellir Power Plant in SW-Iceland. The gases are dissolved in water and injected into the subsurface for permanent storage via mineralization. This requires a thorough understanding of the porosity and the permeability in the system prior to injection. Mapping of the geological factors which affect these properties provides information on the most prominent permeable structures and flow paths of the reservoir. New data from wells in the Nesjavellir high temperature field in SW-Iceland support previous studies which link permeability in the production zone to intermediate intrusions. Furthermore, the new data indicate that faults identified on the surface can be traced to a depth where circulation losses occurred during the drilling of new production wells. This paper presents the current knowledge on the porosity and the permeability properties of the Nesjavellir high temperature field, which have been identified and mapped including this new data. These results will be used as an input into both the reservoir modeling and the geochemical modeling of the area, which will be done prior to the CO2 and H2S re-injection to ensure successful operations at the site.