Study of CO2 solubility enhancement by nanomaterials in carbonated water: Implications for enhanced oil recovery and CO2 storage

Carbonated water injection (CWI) is a promising method for coupled enhanced oil recovery and CO2 geological storage. Nanomaterials can efficiently improve CO2 absorption in conventional absorbents. Therefore, there could be a possibility for using nanomaterials to increase CO2 solubility in carbonated water (CW) and thereby enhance oil recovery and CO2 storage capacity. In this study, the stabilities of different nanofluids and nanomaterial-enhanced CW were examined by the Zeta potential, particle size, high-pressure and high-temperature visual observation, and transmittance measurements. Then, a series of CO2 mass transfer and sol-ubility experiments were conducted in a PVT cell to evaluate the feasibility of enhancing CO2 solubility in CW by nanomaterials and to study the effects of nanomaterial type, concentration, initial pressure, and temperature. Finally, a model was proposed to calculate the diffusion coefficients, pseudo-diffusion coefficient, and CO2 solubility in CW under various conditions. The results revealed that the SiO2-enhanced CW exhibited better stability compared with Al2O3, TiO2, and MWCNT-enhanced CW. For the 0.1 wt% SiO2-enhanced CW at experimental conditions (12 MPa and 30 degrees C), the ES is 1.17, indicating that the CO2 solubility in SiO2-enhanced CW is enhanced by 17% compared with that in CW because of Brownian motion, shuttle effect, and hydrody-namic effect. Increasing the temperature has a negative influence on the CO2 solubility of SiO2-enhanced CW, while an increase in pressure improved the CO2 solubility capacity. The maximum and average relative error percentages between the calculated and experimental CO2 solubility in SiO2-enhanced CW are 10.65% and 3.18%, respectively, indicating the accuracy of the model to determine the CO2 solubility in SiO2-enhanced CW.