Experimental Determination of Equilibrium Interfacial Tension for Nitrogen-Crude Oil during the Gas Injection Process: The Role of Temperature, Pressure, and Composition

Nitrogen has emerged as a competitive gas injection alternative for gas-based enhanced oil recovery processes in the past two decades. The injection of nitrogen into the reservoirs has improved the oil recovery efficiency in various oil reservoirs from heavy to volatile oils. As it is known, interfacial tension (IFT) plays a key role in any enhanced oil recovery process, particularly gas injection processes; therefore, its accurate determination is crucial for the design of any gas injection process especially at reservoir condition. In this study, an axisymmetric drop shape analysis (ADSA) was utilized to measure the equilibrium IFTs between crude oil and N-2 at different temperature levels (313.15 K to 373.15 K) and pressure conditions (1.37 MPa to 39.98 MPa). Besides, the effects of paraffin groups, asphalteneresin ratio, and the colloidal instability index (CII) of crude oils were studied on the IFT behavior of crude oil/N-2 systems. The results showed that the IFT has a decreasing trend with temperature. Moreover, the IFT decreases linearly with pressure in two distinct pressure regions, with two different slopes. Besides, the results indicated that the paraffin groups crucially affect the IFT behavior of the crude oil systems. Additionally, it was found that the higher the asphalteneresin ratio is, the more is the risk of asphaltene precipitation. Furthermore, it was illustrated that the probability of asphaltene precipitation is higher during carbon dioxide injection compared to nitrogen injection.