Ali Naderi Beni

System analysis of underground CO2 storage by numerical modeling for a case study in Malmö

We present a fully compositional, three-dimensional (3D) numerical modeling of an on-shore deep saline formation for system analysis of CO2 storage. We use data from a reservoir in Malmö, Sweden and analyze the reservoir’s response to the injection of 60,000 t of CO2 over a period of two years under realistic reservoir conditions. This helps to explore possible environmental impacts of a future CO2 sequestration test project for the study area. We focus mainly on fluid and mass transports. The results show that the pore overpressure does not exceed a level considered critical for the creation of hydraulic fractures. Our study also indicates how the amount and extent of salt precipitation near the injection well may be altered by variations in relative permeability and capillary pressure. We show that the temperature and strata inclination’s effects are marginal. Further, results indicate a great potential for reactions between CO2, water, and rock. In summary, this numerical simulation addresses both transport and precipitation of salt dissolved in the fluid. Therefore, it provides both a better understanding of the fate of the CO2 plume in a reservoir in time and guidance for practical decisions.

The Influence of Temperature on Chemical Fluid-Rock Reactions in Geological CO2 Sequestration

For a Bunter formation in the German Federal State of North Rhine Westphalia, we use numerical models to consider reactions between the supercritical, aqueous, and solid phases. These reactions may occur in a CO2-water system representing a saline aquifer CO2 storage scenario. Thus, the models are used for determining the extent of fluid–rock reactions during mineral dissolution or precipitation. In particular, we study the effect of temperature by comparing results for our system set at 100 °C and at 58 °C. Results show that the abundance of dissolved ions changes as a result of elevated temperature. For the entire 10,000-year simulation period, the overall geochemical behavior of the Bunter reservoir rock at the Minden site is explained in terms of different mineral transformations, although some of them are not changed significantly. This mainly comprises the alteration of carbonate minerals such as calcite, and aluminium silicates such as oligoclase, chlorite, illite, albite, kaolinite, and Na-smectite. Another chemical behavior derives from the generation and consumption of new secondary minerals such as dawsonite, pyrite, and Ca-smectite. In contrast to a system temperature of 58 °C, the mineralogical transformations of other minerals such as siderite, ankerite, dolomite, and magnesite are not observed at 100 °C. Also, the numerical simulation results show that at elevated temperature, the dominant role played by hydrodynamic mechanism dwarfs the role of other trapping mechanisms including dissolution and mineralization. Results also demonstrate how geological, petrophysical, and geochemical data can be integrated to estimate quantitatively the magnitude of the fluid–rock reactions. These reactions may entail new geotechnical problems, such as rock self-fracturing which ultimately decreases the CO2 sequestration projects security.