Short-term effects of impurities in the CO2 stream injected into fractured carbonates

Abstract After the Paris Agreement in which 195 countries are involved, the Carbon Capture and Storage (CCS) is now an accepted technology in the United Nations Framework Convention on Climate Change (UNFCCC). In Spain, Fundacion Ciudad de la Energia (CIUDEN) has successfully completed the full CCS chain, being CO 2 captured in the Technology Development Centre in Cubillos del Sil ( Leon , Spain) whereas that it is geologically stored in a deep saline aquifer, formed by fractured carbonates with poor matrix porosity, located in the Technology Development Plant (TDP) at Hontomin (Burgos, Spain). The results of the field tests, in which up to 150 t of CO 2 and synthetic air (5%v of N 2 and O 2 ) were co-injected on site, are analyzed in this paper comparing the operational parameters gained during the injection of impure CO 2 (pressures, temperatures and flow ranges) with its corresponding baseline previously determined (i.e. 1500 tons of pure CO 2 were injected during the reservoir hydraulic characterization). Besides that, the geochemical reactivity analysis of impure CO 2 injected in this saline aquifer and its correlation with the results from laboratory tests were assessed. As main conclusions from laboratory scale results, a porosity diminution was measured after the injection of CO 2 with 5%v of SO 2 ; apart from that, without SO 2 , the effluent pH was in the range of 7–8 whereas in case of CO 2 and SO 2 , a pH of 1–2 was obtained. Otherwise and focused on field scale tests, a density decrease was detected comparing the base case (pure CO 2 ) with the CO 2 injection containing 5.1%v of synthetic air. On the other hand, Ca 2+ , SO 4 2− , Mg 2+ and K + migration effects in the rock were also detected and analyzed.