Effects of Dissolved CO2 on the Crude Oil/Water Interfacial Viscoelasticity and the Macroscopic Stability of Water-in-Crude Oil Emulsion

In CO2 flooding, the dissolution of CO2 in produced fluid may change the stability of crude oil emulsion, thereby affecting the design/operation of the gathering pipeline and oil–water separation. The purpose of this study is to investigate the stability change of crude oil emulsion and its mechanisms after the dissolution of CO2. The stability of the CO2-dissolved crude oil emulsions is determined with a self-made apparatus. The mechanisms of the stability change are uncovered from interfacial properties and bulk viscosity. It is found that the stability of the crude oil emulsions is visibly reduced with an increasing dissolved quantity of CO2. This is partly attributed to the fact that dissolved-state CO2 can lessen the interfacial dilational modulus and increase the loss angle markedly, thus lowering the structural strength and elasticity of the interface. Meanwhile, the dissolution of CO2 in crude oil can reduce its viscosity, resulting in easier collision of droplets. In view of these experimental re...