Reaction of CO2 with Formation Water Scale Deposit and CO2-Water-Rock Interaction in Sandstone Reservoirs of the Junggar Basin, Western China

The CO2 injection capacity is a crucial parameter for assessing CO2 geological storage. The occurrence of scaling phenomenon and CO2-water-rock interaction subsequent to CO2 injection into the reservoir impact the porosity and permeability of the reservoir, and consequently, the injection capacity of the reservoir. Existing research has shown limited focus on scaling phenomenon, with a significant lack of studies investigating the scaling mechanism. A comprehensive exploration of scaling phenomenon and the quantification of their effects, alongside CO2-water-rock interaction, on the injection capacity of reservoirs, hold significant importance for CO2 geological storage. This paper aims to investigate the influential factors of the scaling phenomenon through experiments conducted in a sandstone reservoir in the Xinjiang oilfield. This study aims to evaluate the impact of scaling phenomenon and CO2-water-rock interaction on reservoir porosity and permeability and to assess the capacity for CO2 sequestration through numerical reservoir modeling. The experimental results indicate that the amount of scaling increases with rising temperature and decreases with the increase in the CO2 partial pressure. Furthermore, simulation results demonstrate the accumulation of free supercritical CO2 at the base of the cap rock due to buoyancy, while liquid-phase CO2 is primarily transported by molecular diffusion and convective mixing. The dissolution of feldspar, calcite, and chlorite leads to the precipitation of the carbon-fixing mineral ankerite alongside other minerals, resulting in a reduction of reservoir porosity by 1.4% and permeability by 4.0%, and subsequently a decrease in reservoir injection capacity. The scaling phenomenon diminishes reservoir porosity and permeability by 0.2% and 0.13%, respectively, an almost negligible impact. The maximum CO2 storage under simulated reservoir conditions is 41.8 mol/kg medium, which has good storage potential. This study contributes to the comprehension of the effects of scaling phenomenon and CO2-water-rock interaction on reservoir injection capacity.