Comparison of Residual Oil Saturation for Water and Supercritical Co2 Flooding in a Long Core, With Live Oil at Reservoir Conditions

The measurement of residual oil saturation (ROS) is of paramount importance in predicting the expected recovery in a producing field. It is also a key factor for reservoir management and for defining possible long-term enhanced oil recovery (EOR) targets. Even though ROS has been known to depend on different factors, such dependence has not been investigated extensively in the laboratory, at reservoir conditions. This paper describes an experimental work focusing on the rock formation and conditions of a very highly productive field that is offshore Brazil. The objective was to compare the recovery efficiency between water and supercritical CO2 flooding at reservoir conditions in terms of ROS evolution. A careful program of displacement tests was conducted using long real unconsolidated porous media and live reservoir fluid at reservoir pressure and temperature. An improved version of a conventional test apparatus has been implemented successfully to allow high pressure displacements through long cores. A linear x-ray monitoring device permitted us to follow water and CO2 in situ saturations along the core. A numerical simulation study was developed to scrutinize possible effects from varying conditions. The results obtained in this work led to lower residual oil saturation in the CO2 flooding than water flooding. Experimental and numerical simulation results are compared.