Gas/Oil Relative Permeabilities and Residual Oil Saturations in a Field Case of a Very Light Oil, in the Near-Miscibility Conditions

Abstract

ABSTRACT The Hassi-Messaoud Field is one of the biggest oil fields in the world, made to produce by miscible gas flooding since 1964, a few years after the beginning of production. In some blocks, the pressure decline has been very great and such that pressure is currently close to the minimum miscibility pressure (MMP). Laboratory studies were undertaken on representative core samples with the reservoir fluids to determine the gas/oil relative permeabilities and residual oil saturations (Sorg) at different levels of pressure, below the MMP. The recombined oil samples were prepared with the same stock tank oil and two separator gases, one of them containing significantly more intermediates than the other. The two recombined oils had the same bubble-point pressure. The MMP was measured for these two different oils with an injection gas called "medium gas", produced on the field itself. The high sensitivity of the MMP to the associate gas composition has been outlined. The Sorg values were very low (between 25 and 5% PV) depending on the initial oil composition and on the level of pressure. A correlation has been established between the observed Sorg and the difference between the pressure of each test and the MMP versus the MMP. Finally, this study has demonstrated that the gas flooding process is very efficient even if the miscibility is no longer reached, while staying however in near miscibility conditions.