Experiments on the minimum mixing pressure of CO₂ and mixed alkane by using the interfacial tension regression method

Alkanes in Awaz-Banguistan crude oil from an oil field in southwestern Iran were simulated without considering asphaltene. At 40 ℃ and 60 ℃, and pressure ranges of 3.0-8.5 MPa and 3.0-9.5 MPa, the interfacial tensions between mixed alkane and CO₂ saturated by NaCl solution were measured by combining the traditional high-pressure pendant drop method and advanced computer image processing software. The corresponding minimum mixing pressure(MMP) was obtained by extrapolation. The feasibility of the method was successfully verified and the experimental results were discussed by comparing with literatures. The analysis are mainly carried out from two factors that affect the change trend of interfacial tension with pressure, i.e. crude oil composition and temperature. It is concluded that low carbon n-alkanes can accelerate the decrease of interfacial tension with pressure, and the formation of pressure key points is caused by comprehensive factors affecting interfacial tension at high temperature.