Impact of gas composition, pressure, and temperature on interfacial Tension dynamics in CO2-Enhanced oil recovery

Climate change policies are driving the oil and gas industry to explore CO2 injection for carbon dioxide storage in reservoirs. In the United States, a substantial portion of oil production relies on CO2-enhanced-oil-recovery (CO2-EOR), demonstrating a growing interest in using CO2 to address various production challenges like condensate mitigation, pressure maintenance, and enhancing productivity in tight reservoirs. CO2 injection introduces gases like natural gas and N-2, either pre-existing or as impurities in the injected CO2 gas. These gases alter the interaction of CO2 with the oil or condensate in the reservoir, with interfacial tension playing a crucial role in governing miscibility, mobilization, and phase distribution. Effectively implementing gas injection techniques requires a precise understanding of interfacial tension between injected gases and reservoir fluid under reservoir conditions. This study aims to evaluate the effects of oil composition, gas composition, pressure, and, temperature on interfacial tension and provides a comprehensive understanding of IFT dynamics for CO2-EOR implementation. The study utilizes the pendant drop analysis technique to assess the impact of pressure, temperature, and gas composition on crude oil and condensate interfacial tension. Measurements span a range of temperature (30-85 C-o), pressure (0.7-7 MPa), and mixture composition (CO2: N-2 ratios of 90:10 and 10:90), including pure CO2 and N-2 with crude oil and condensate. Accurate measurement of interfacial tension incorporates changes in oil and gas density as functions of pressure and temperature. Results show that interfacial tension is significantly influenced by pressure, temperature, and gas composition. It decreases with increasing pressure at constant temperature and gas composition for both crude oil and condensate. While temperature-induced reductions in interfacial tension occur, they are overshadowed by the more pronounced effect of pressure. Gas composition significantly affects system interfacial tension; an increase in CO2 mole fraction decreases it, while an increase in N-2 mole fraction causes an upturn. Changes in CO2 mole fraction result in concave downward trends, whereas changes in N-2 mole fraction lead to concave upward trends. These findings are crucial for understanding the interaction of injected gas with reservoir fluid and can be applied to model interfacial tension with hydrocarbon fluid. This study offers an in-depth understanding of interfacial tension dynamics in CO2-EOR, a process that is increasingly attracting global attention for CO2 utilization. The research stands out for its innovative experimentation and detailed analysis, which focus on evaluating the impact of individual parameters crucial for modeling. Additionally, it sheds light on the combined effects of these parameters, which are essential for practical field applications. This knowledge is instrumental in designing processes such as CO2-EOR and condensate banking, incorporating the effects of pressure, temperature, and gas composition at the reservoir scale.