Carbonated water injection (CWI) is a promising enhanced oil recovery (EOR) and CO₂ sequestration method, which overcomes the problems associated with CO₂ EOR. CO₂ mass transfer and interfacial tension (IFT) are important parameters that influence oil recovery efficiency. This study addresses the impact of MgCl₂ and Na₂SO₄ in carbonated water (CW) on CW/hydrocarbon IFT and CO₂ mass transfer. An axisymmetric drop shape analysis was used to estimate the IFT and the CO₂ diffusion coefficient. It was found that CW+MgCl₂ reduced both the CW/n-decane IFT (36.5%) and CO₂ mass transfer, while CW+Na₂SO₄ increased both the IFT and CO₂ mass transfer (57%). It is suggested that reduction in IFT for CW+MgCl₂ brine is mainly due to the higher hydration energy of Mg²⁺. The Mg²⁺ ion forms a tight bond to the first hydration shell [Mg(H₂O)₆]²⁺, this increases the effective size at the interface, hence reduce IFT. Meanwhile, the SO₄²⁻ outer hydration shell has free OH groups, which may locally promote CO₂ mass transfer. The study illustrates the potential of combining salts and CW in enhancing CO₂ mass transfer that can be the base for further investigations. Furthermore, the contribution and proposed mechanisms of the different ions (SO₄²⁻ and Mg²⁺) to the physical process in carbonated water/hydrocarbon have been addressed, which forms one of primary bases of EOR.

The objective of this study is to address the influence of different CO₂ phases and degrees of CO₂ saturation on the interfacial tension and the diffusion of CO₂ into a hydrocarbon drop.

A numerical model was developed to investigate the influence of gravitational force on the transport of colloids in a single horizontal fracture–matrix system. Along with major transport phenomena, prominence was given to study the mass flux at the fracture–matrix interface, and colloid penetration within the rock matrix. Results suggest that the gravitational force significantly alters and controls the velocity of colloids in the fracture. Further, it was shown that the colloid density and size play a vital part in determining the extent that gravity may influence the transport of colloids in both fracture and rock matrix. The mass flux transfer across the fracture–matrix interface is predominantly dependent on the colloidal size. As large as 80% reduction in penetration of colloids in the rock matrix was observed when the size of the colloid was increased from 50–600 nm. Similarly, the farther the density of colloid from that of the fluid in the fracture (water), then the higher the mitigation of colloids in the fracture and the rock matrix. Finally, a non-dimensional parameter “Rock Saturation Factor” has been presented in the present study, which can offer a straightforward approach for evaluating the extent of penetration of colloids within the rock matrix.