High Pressure Data and Modeling Results for Phase Behavior and Asphaltene Onsets of GoM Oil Mixed with Nitrogen

Abstract

Abstract This paper presents high pressure PVT measurements and equation-of-state (EoS) modeling results for a GoM oil and for the oil mixed with nitrogen in various concentrations. The data includes: Upper and lower asphaltene onset pressures and bubble point pressures for the reservoir fluid swelled with nitrogen. At the reservoir conditions of 94 MPa (13,634 psia) and 94°C (201.2°F) asphaltene precipitation is seen after addition of 27 mole % of nitrogen. Viscosity data for the swelled fluids showing that addition of nitrogen significantly reduces the oil viscosity. Slim tube runs indicating that the minimum miscibility pressure of the oil with nitrogen is significantly higher than estimated from published correlations. The data has been modeled using the volume corrected Soave-Redlich-Kwong (SRK) and the Perturbed-Chain Statistical Association Fluid Theory (PC-SAFT) EoS. While both equations provide a good match of the PVT properties of the reservoir fluid, PC-SAFT is superior to the SRK EoS for simulating the upper asphaltene onset pressures and the liquid phase compressibility of the reservoir fluid swelled with nitrogen. Nitrogen gas flooding is expected to have a positive impact on oil recovery due to its favorable oil viscosity reduction and phase behavior effects.