A Novel Carbon Sequestration Stability Assessment Technique of Co2 Geological Utilization and Storage with Clarified the Connectivity

CO 2 enhanced oil recovery (CO 2 -EOR) is a potential CO 2 capture, geological utilization and storage technology. In particular, the injected CO 2 can break the balance of water-rock, CO 2 is expected to dissolve into the formation water and even convert into carbonate minerals which is regarded as the stable phase of sequestered carbon. However, the impacts of geochemical reactions on CO 2 -EOR processes is lacking and the fate of CO 2 in difference phases cannot be quantitatively evaluated. In this paper, we propose to consider various possible water-rock geochemical kinetics reactions which affected by three mechanisms in CO 2 -EOR and implemented by coupling the behaviors of oil phase in the porous media with the existing TOUGHREACT. Our analyses employ a realistic fluid property (pressure-volume-temperature, PVT) description of multi-component oil phase-CO 2 mixtures. The simulated model established by the updated program considered the possible geochemical reactions and the resulting changes in porosity and permeability. Furthermore, the engineering conditions were set according to the typical oil reservoirs. The results indicated that the initial conditions of the model acquired by linear regression method will at least reduce a 23% error comparing to that of using principle of symmetry. The water-rock interactions in CO 2 -water alternating injection can improve the porosity and permeability, which facilitates the subsequent injection and they are also have effects on pressure. Injected CO 2 has a higher risk of being produced to the surface, and only 33.93% of potentially stable sequestration in one CO 2 -water cycle of 9% HCPV (hydrocarbon pore volume) CO 2 slug, more free CO 2 gas would dissolved in oil phase than aqueous phase. It determined that under the current engineering conditions, CO 2 -EOR is difficult to explain as a good way to realize carbon neutralization. This suggests that the optimization scheme to obtain higher stable sequestering is necessary in the future