Modified vanishing interfacial tension (VIT) test for CO2–oil minimum miscibility pressure (MMP) measurement

Abstract

Miscible gas injection is one of the most popular and applicable enhanced oil recovery method in oil fields. Minimum miscibility pressure (MMP) is an important parameter for an enhanced oil recovery process involving carbon dioxide or hydrocarbon miscible gas injection. There are many methods for measuring MMP but the most standard method for measuring MMP value in oil field gas injection process is slim tube method, which is very time consuming (4–6 weeks). Measurements of the interfacial tension of mixtures of a reservoir fluid and injection gas at various pressures have been proposed recently as an experimental method for predicting the minimum miscibility pressure (MMP) in an experiment called the vanishing interfacial tension (VIT) technique. This method is quantitative in nature and fast (2–3 days) with respect to slim tube method. VIT technique is based on the concept that the interfacial tension between the gas and crude oil phases at reservoir temperature must reduce to zero as these two phases approach the point of miscibility. The concept of zero interfacial tension at miscibility is, in turn, based on the well-accepted fact that the interface between the phases must vanish, as they become miscible with one another.Our results show the MMP value obtained from VIT method exceeds the slim tube MMP and miscibility pressure does not necessarily occur at zero IFT. Using zero IFT criteria cause MMP overestimation. In this study, by using the VIT and slim tube test, we measured the IFT in which slim tube MMP occur in VIT test for CO2–oil system for various types of reservoir oil. These IFT values are correlated by oil properties and test condition to help us measure the accurate value of MMP by using VIT method.