MODELING THE GEOCHEMICAL IMPACT OF AN INJECTION OF CO2 AND ASSOCIATED REACTIVE IMPURITIES (SO2 ANDO2) INTO A SALINE RESERVOIR

Abstract Carbon dioxide storage in deep geological structures is a strategic technology to mitigate climate change and to promote green development. However, despitecontinuous efforts to develop cost effective capture processes to clean the CO2 stream before transportation and injection, traces of accessory gases cannot be entirely removed. Consequently, before any injection of these gas mixtures, the impact of impurities on the geochemical reactivity of the system must be evaluated. This paper describes numerical simulations donewith TOUGHREACT that focus on the chemical reactivity of deep reservoir rock impacted by an injection of CO2 and associated reactive impurities (mainly SO2 and O2). A simplified two-dimensional radial geo-model ofthe near wellbore domain of a saline reservoir enabled us to predictits global geochemical behavior. Two CO2:SO2ratios were studied. The results show the high reactivity of the near-well zone when ancillary gases (SO2 and O2) are co-injected with CO2, which leads to thedissolution of carbonates and the precipitation of sulfateminerals. Major reactions occur in the reservoir formation, whereas clays inthe caprock are only slightly affected by the injection of CO2 and associated reactive impurities