| The increase in global temperature is almost certainly exacerbated by the emission of anthropogenic greenhouse gases, and principally CO2, into the atmosphere. This dissertation will focus on the storage of CO2 in aquifers, which having the highest estimated capacity to store CO2 in geological formations. The efficiency of long-term storage in aquifers will be directly related to the efficiency of each of the trapping mechanisms involved. According to the Sequestration mechanism, this dissertation analyzes interreaction among CO2, saline and variety of influencing parameter are calculated. Selecting the appropriate simulation software, we have established a basic model to study the migration. We present the results of a numerical sensitivity analysis and compare the contribution of the most important parameters to the trapping of CO2. The work focuses on the impact of dissolution and residual trapping.CO2 injected in the bottom of the saline migrate upward until the cover which prevent CO2 further migration. CO2 spreads out underneath the cap rock laterally. These studies show that the dissolution, diffusion and convection impact CO2 storage in aquifers. CO2 injected in the bottom of the saline migrate upward until the cover which prevent CO2 further migration. CO2 migrate along cover. Using a more refined grid, we can see that the free CO2 at the top of the plume will dissolve into the brine. Most CO2 present as free gas and the main trapping mechanisms occur in saline aquifers is structural or stratigraphic trapping.Reservoir conditions, e.g. pressure and temperature influence CO2 dissolution and migration radius. Porosity, permeability and the ratio of vertical to horizontal permeability(kv/kh) have influence on CO2 storage. Higher porosity and permeability allows the CO2 plume to be distributed laterally over a larger area, enhancing solubility and residual trapping. At low values of kv/kh, CO2 tends to migrate laterally in the injection layers, whereas an increase in this ratio enhances the vertical migration and CO2 spreads out underneath the cap rock laterally. Hysteresis, capillary force and residual gas saturationis found to be the greatest contributor to the amount of residual CO2. As expected, higher hysteresis, capillary force and residual gas saturation will reduce CO2 mobility, producing a higher residual trail left by the CO2 plume as it migrates. At the same injection ratio, reservoir thickness of sequestration is not a particularly large impact. The dipping and the buoyancy of the CO2 make the plume migrate upwards rapidly and come into contact with larger volumes of fresh brine. Break is good for preventing CO2 migration.Injection parameters also have impact in CO2 storage. The less of CO2 is injected per day, the faster the CO2 plume travels. This can increase the mobility contrast between the brine and CO2 causing more CO2 to be dissolved. Location and number of the injection well are not important for carbon sequestration. CO2 storage in the saline need one injection well. Comparing to deviated wells and vertieal wells, horizontal wells are better choices for CO2 injection and storage. The deeper the well completion, the longer the path for the CO2 plume to reach the top of the structure, and in consequence larger volumes of water and a larger distribution benefits both trapping mechanisms. |
PDF Full Text Request