Interfacial Tension of Nitrogen/Volatile Oil Systems

This paper presents interfacial tension (IFT) measurements of a nitrogen/volatile oil system at conditions that are typical for North-Sea oil reservoirs. The volatile oil is a well-defined three-component oil, which can be displaced by nitrogen in a developed miscible manner. Using the pendant drop method, we have measured the IFT of the nitrogen/volatile oil system at four characteristic compositions at a constant temperature of 100°C and in the pressure range of 30 MPa to 40 MPa. For the analysis of the pendant drops we have used advanced image processing techniques. Depending on composition and pressure, we have measured IFTs as low as 0.05 mN/m with an accuracy less than 2%. Predictions of the IFT of our fluid systems with the parachor method and with Lee & Chien's method show large deviations from the experimental values. At near-critical conditions, the nitrogen/volatile oil system behaves in accordance with critical scaling theories.