Experimental measurement of equilibrium interfacial tension of enriched miscible gas-crude oil systems

During the design of an enhanced oil recovery (EOR) method in a particular gas flooding project, measuring interfacial tension between injected gas and live reservoir oil samples is essential for estimating optimum miscible gas injection scenarios at reservoir conditions. In this study, during an experimental miscible gas injection project for one of the Iranian oil fields, natural liquefied gas (NGL) and Naphtha were selected to enrich injecting gas in order to study the gas composition impact on efficiency of miscibility process. Therefore, injecting gas was enriched by recombining with NGL and Naphtha samples with predefined ratios. Afterward, an axisymmetric drop shape analysis (ADSA) was utilized to measure interfacial tension between reservoir oil and five synthesized gas samples at depletion pressure steps and constant reservoir temperature. The results showed the optimum miscible gas enrichment scenario with minimum interfacial tension at depletion pressure steps. Additionally, recombining injecting gas sample with NGL led to reduce interfacial tension more effectively than recombined samples with Naphtha. The results of this study are helpful for successful design of gas injection scenarios in this filed, and reveal the role of gas composition in the IFT behavior of crude oil systems.