Effect of Salts on Interfacial Tension and CO2 Mass Transfer in Carbonated Water Injection

Resumen

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.