Application of CO2-Saturated Water Flooding as a Prospective Safe CO2 Storage Strategy

In this study, According to the results of CO2 solubility measurement tests at constant temperatures, an increase in CO2 solubility values was observed for CO2-brine and CO2-oil systems when the equilibrium pressure increases. Furthermore, it was revealed that for both aforementioned systems, the solubility of CO2 reduces when temperature increased. It was found that introducing CO2 to the oil reservoirs through injection water provides great opportunity to lock large quantity of CO2 inside the porous medium with high retention factor. Results of this study showed that both secondary and tertiary scenarios of CO2-saturated water flooding are favourable with the storage capacity between 34% to 45% of the injected CO2 in the sand-pack model. In addition, the solubility trapping was shown to be the main CO2 trapping mechanism during CO2-saturated water flooding. According to the results of this study, most of the injected CO2 was trapped in the porous medium through dissolution in the reservoir fluids, i.e., solubility trapping. As an example, the flooding tests conducted in secondary mode at P = 10.3 MPa and T = 25 degrees C, showed that about 95% of the injected CO2 can be trapped by dissolution mechanism into the reservoir oil and brine. In terms of oil recovery, it was found that the ultimate oil recovery factor of CO2-saturated water flooding is consistently more than that of conventional water flooding leading this technique to be a more viable option as a means of improved oil recovery technique. In this study, flooding tests conducted at pressure of P = 10.3 MPa and temperature of T = 25 degrees C, verified that injection of CO2-saturated water resulted in improving the conventional water flooding oil recovery factor by about 19.0% and 12.5% of OOIP for secondary and tertiary scenarios, respectively. Based on the results obtained in this work, it was concluded that mixing CO2 with injected water noticeably provides permanent, safe, and practical CO2 storage together with considerable oil recovery improvement in light oil systems. (C) 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).