Use of oil-soluble surfactant to reduce minimum miscibility pressure

ABSTRACT

In some low-permeable reservoirs, the miscibility pressure is far higher than the formation pressure, which makes it not feasible to have a CO₂ miscible displacement. In this study, an oil-soluble surfactant, CAE, was designed and synthesized to reduce interfacial tension (IFT) and CO₂-oil minimum miscible pressure (MMP), making it possible to release miscible displacement increasing oil recover. Experiment results showed that oil soluble surfactant can be dissolved in supercritical CO₂ but not soluble in water. It is also found that the CAE preslug displacement has the higher displacement efficiency than displacement with the CAE dissolved in CO₂. Based on a series of CAE preslug displacement experiments with varying CAE concentrations, the optimal injection concentration of CAE is 0.2%. Moreover the MMP determined under the CAE concentration of 0.2% is 6.1 MPa lower than that of pure CO₂ displacement. It reduces the MMP more than liquid gas preslug displacement (3.2 MPa) when the same volume of liquid gas is used with the CAE used in CAE preslug displacement test.

KEYWORDS:

• Displacement pattern
• minimum miscible pressure
• oil-soluble surfactant
• Slim tube test
• viscosity reduction

Funding

This research was supported by National Science Foundation of China (No. 51374179).