Numerical simulation of industrial scale CO 2 -H 2 S injection into basalts at Hellisheidi, SW-Iceland David Stevens 1,2*, Edda S.P. Aradttir 1 Introduction - Objectives CO 2 -H 2 S mineral sequestration in basaltic rocks may provide a long-term and thermodynamically stable geological sequestration option. Within CO 2 -REACT Marie-Curie EU network and in collaboration with LBNL, the aim of this project is to develop reactive transport models of the up-scaled injection activities at Hellisheidi geothermal power plant and thus to carry out predictive mass and reactive transport simulations. * address: CO2REACT webpage:1 Reykjavk Energy, 2 Science Institute of the University of Iceland, Background - Pilot injections in Hellisheidi CarbFixI Experimental CO 2 and H 2 S injection field; rates mineral sequestration in a basaltic layer between m depth [1]. Development of a solubility trapping technology [2]. SulFixI Development of methods and technology for CO 2 and H 2 S mineral sequestration in basalts below 1000 m depth, experimental field injection[1]. The up-scaled injection will start in the coming month at the SulFix site. Figure 3 Aerial map of CarbFix and SulFix injection sites. HN-02 and HE-08 are CarbFix and SulFix injection wells, respectively. Other wells are observation wells. Fresh groundwater, used for dissolving gases in CarbFix is pumped from well HN-01. Separated geothermal water from HE-05 is used for dissolving gases at SulFix. Injection wells deviation is depicted by red lines. Combed lines represent faults [1]. Conceptual Hydrogeological Models Numerical modeling plays an important role in on-going injection activities at Hellisheidi as it provides tools to predict and optimize long-term management of injection sites as well as to quantify mineral trapping process. SulFix * The reservoir is a sub-glacial formed hyaloclastite with occasional lava series. Tracer tests highlight some fast flow values (typical from a fractured formation) within the host rock formation [1] *. Figure 1 CGS storage security (IPCC, 2005) Figure 2 Metallic ions in basalt and certain other rocks lock CO2 and H2S into stable mineral forms (Image credit: Peter McGrail, Pacific Northwest National Laboratory) Figure 6 Schematic of the conceptual one-dimensional dual porosity model used for Sulfix simulations (top) and illustartion of elements and connections in the developed model (bottom) [1]. Figure 5 Well logs for SulFix injection well HE-08 [1]. * * NB: Development of reactive transport models for the SulFix project has only recently begun and the models needs to be refine by some geological surveys and tracer tests. Geochemistry Alteration minerals in Hellisheidi are in agreement with the commonly observed hydrothermal alteration of basalts in Iceland (clay minerals and zeolites, calcite and amorphous silica, quartz and/or chalcedony) [1]. A thermodynamic dataset describing 36 mineral reactions of interest was developed by Aradttir et al. (2012) within CarbFix project. However, CO 2 - REACT partners are developing a more comprehensive database that will be integrated in the numerical models. Acknowledgements This work was supported by Reykjavik Energy, and the Science Institute of the University of Iceland. References [1] Aradttir, E.S.P. et al. manuscript in review [2] Sigfsson B et al. manuscript in review [3] Aradttir, E.S.P. (2011). Ph.D. thesis, University of Iceland. Computational code TOUGHREACT, TOUGH2 and iTOUGH2 codes will be used for developing models. The TOUGH codes is a family of simulation tools for multiphase flow and transport in permeable media. TOUGHREACT can be used for developing multi-dimensional reactive transport models [3]. Model development TOUGH2 and iTOUGH2 will be used for developing two and three dimensional field scale mass transport models of the SulFixII injection site at Hellisheidi. Hydrological properties of the reservoir will be calibrated using iTOUGH2. TOUGHREACT reactive chemistry code will be coupled with mass transport models in order to run numerical predictive mass transport and reactive transport simulations [2]. Industry Application Reducing greenhouse gases from high-enthalpy geothermal plants aims to follow considering this energy as a green one and basalts may act as ideal geological CO 2 and H 2 S storage formation [1]. This strategy aims to meet the Icelandic regulation on atmospheric H 2 S concentration [1]. Positive results could ensure CCS technology by validating in situ CO 2 -H 2 S mineralization process in basalts and ultramafic rock formations. Furthermore, geological carbon/hydrogen sulfide sequestration could constitute an environmental tool/product for polluting industry such as iron/steel, cement, glass/industrial heat users, chemical/refineries, coal power plants Up-scaled injection at Hellisheidi Industrial scale injection activities at Hellisheidi involve capturing 15-20% of CO 2 -H 2 S from the power plant and injecting it back into the geothermal reservoir below 800m depth. A gas separation station will use condensate from the power plant for separating CO 2 -H 2 S from less soluble exhaust gases (H 2, N 2 and Ar). Approximately 400g/s of gas mixture (70% CO 2 and 30% H 2 S) dissolved in 30kg/s condensate will enter the storage formation at temperature higher than C. Hydrogeological primary setups [1] More tracer data will be available and used for calibrating more complex numerical models. SulFix flow setup FracturePorous media (Matrix) Permeability = 7, m 2 Porosity = 2,5% Diameter = 2 mm Permeability = 0, m 2