On the Possibility of Implementing CCS Projects in the Carbonate Reservoirs of the Siberian Platform

Abstract

Relevance: Carbon capture and storage technology involving geological storage of carbon dioxide in deep aquifers is widely used in the world as this technology is aimed at reducing the emission of greenhouse gases into the Earth’s atmosphere and minimizing the influence of these gases on global climate change. Objective: To carry out preliminary investigation of the features of water–rock–carbon-dioxide interactions in application to carbonate reservoirs, which are widespread in hydrogeological basins over the territory of the Russian Federation and are potentially suitable as carbon dioxide storage facilities. These processes are considered on the example of the ancient Siberian Platform, where industrial production of hydrocarbons is currently increasing and a series of large-scale projects in the area of petroleum and gas chemistry are underway. Methods: Mathematical physical and chemical modeling is applied to solve the problem. The calculations are implemented by the HydroGeo software package, in which the achievement of chemical equilibria for the “water–rock” system is implemented on the basis of the method of equilibrium constants. Results: The obtained results allow us to evaluate the directions of geochemical processes in the reservoirs under consideration and to provide qualitative estimation of changes in the pore space under the conditions of its saturation with carbon dioxide, with respect to different saturation degrees. It is established that solution acidification is observed as a result of its saturation with CO₂, with the transition of chemical elements to the prevailing forms of complex ions bound with hydrocarbonate and chloride ions (Mn, Na, K). At the same time, saturation with carbon dioxide does not have such a substantial effect on the forms of Ca and Fe migration. Special attention is paid to Al, which is transformed almost completely from complex forms into Al³⁺ in the presence of carbon dioxide. In the studied reference samples, rather intense transformation of the reservoir rocks with redistribution of elements between the primary and secondary mineral phases is observed (both rock dissolution and precipitation up to several hundred g/dm³) with comparatively small absolute changes in open porosity. In a number of the considered objects, the dissolution of calcite and dolomite proceeds due to a decrease in pH. The directions of the transformations, as well as the trend of changes in the filtration-capacity properties, are determined by the specific mineralogical combination of the reservoir rocks and the brine present in them, as well as by the stage of evolution of the system under consideration (the first part of the considered combinations is initially far from equilibrium and continues interacting, while the second part is close to equilibrium and is transformed into the non-equilibrium state due to saturation with carbon dioxide).