Fluid Phase Equilibria, Vol.356, 78-89, 2013
Temperature effects on the phase behaviour, mutual interactions and oil recovery of a light crude oil-CO2 system
In this paper, the temperature effects on the phase behaviour, mutual interactions, and oil recovery of a light crude oil-CO2 system are experimentally studied. First, six PVT tests are performed to measure the saturation pressures and the oil-swelling factors of three light crude oil-CO2 systems with different CO2 concentrations. Second, a series of saturation tests are conducted to determine the onset pressure (P-asp) of asphaltene precipitation from the light crude oil-CO2 system. Third, the minimum miscibility pressure (MMP) and the first-contact miscibility pressure (P-max) of the light crude oil-CO2 system are determined by applying the vanishing interfacial tension (VIT) technique. Meanwhile, the oil-swelling effect, the initial quick and subsequent slow light-hydrocarbons extraction phenomena are observed during the dynamic interfacial tension (IFT) measurements. In particular, the onset pressure (P-ext) for the initial quick light-hydrocarbons extraction by CO2 is noted. Finally, a total of eleven CO2-coreflood tests are undertaken to examine the temperature effect on the CO2-based oil recovery. All the above-mentioned experiments are conducted at a laboratory temperature of T-lab = 27.0 degrees C and at the actual reservoir temperature of T-res = 53.0 degrees C, respectively. It is found that the test temperature has a strong effect on the saturation pressure but a marginal influence on the oil-swelling factor of a given light crude oil-CO2 system. It is also found that the four onset pressures are in the order of magnitude: P-asp < P-ext < MMP < P-max. Furthermore. P-asp and P-ext increase slightly but the MMP and P-max increase significantly with the test temperature. Lastly, a higher test temperature leads to a higher oil recovery factor as long as the CO2 flooding is miscible. (C) 2013 Elsevier B.V. All rights reserved.
Keywords:CO2-EOR;Asphaltene precipitation;Light-hydrocarbons extraction by CO2;Minimum miscibility pressure (MMP);First-contact miscibility (FCM) pressure