Аңдатпа
Understanding the geochemical interactions among injected CO 2 , rock, and brine water is one of the essential factors for the safe and proper operation of CO 2 storage in depleted oil reservoirs. The interactions can alter their original geochemical and physical environmental factors and therefore significantly affect the safety and efficiency of the sequestration process. We sampled the formation rock (sandstone) and fluid (pH 6) at an insitu reservoir condition from an oil reservoir of Kazakhstan, Ebeity (863 -894 m) for this research. The CO 2 injection to the depleted oil well and its storage were numerically simulated using geochemical software. PHREEQC was used to estimate the interaction among rock-water-CO 2 phases and the dissolution and precipitation of rock minerals, porosity change, and water composition alteration were investigated. 1-D radial model was developed and implemented via TOUGHREACT to investigate the fate of injected CO 2 and its influence on surrounding minerals and water over a distance, and to check potential for permanent sequestration at a constant rate of 100 kt/year for 50 and 10000 years. Albite, anorthite, k-feldspar, kaolinite, calcite, and smectite minerals were dissolved during the injection and storage, while secondary mineral such as dolomite, muscovite, ankerite, quartz, and dawsonite were precipitated. Porosity change was also estimated, i.e. ~4% of porosity decrease was observed during the carbon sequestration operation. Reactive transport modeling showed the decrease of surrounding storage pH by CO 2 injection over a radial distance and remarkable change of original minerals to secondary minerals. As 50 years passed after the injection, only ~10% of CO 2 mass was able to be dissolved at the storage site, whereas after 10,000 years, the total dissolution of CO 2 can be estimated by the simulation model. The results can provide a detailed understanding on the behaviors of injected CO 2 and variations of surrounding geochemical environments during the operation of carbon sequestration.