An Experimental Study of Secondary WAG Injection in a Low-Temperature Carbonate Reservoir in Different Miscibility Conditions

Abstract

This experimental study is aimed at evaluation of the performance of secondary WAG injection in carbonate cores at different pressures. To do so, a comprehensive series of high-pressure high-temperature (HPHT) core flooding tests are conducted. The fluid system includes reservoir dead and live crude oil, CO₂, and synthetic brine while the chosen porous media consists of a number of fractured carbonate core samples. Parameters such as oil recovery factor, water and oil production rates, and pressure drop along the core are recorded for both dead and live oil. According to results, at first increasing pressure improves the oil recovery, but this improvement after MMP is not as significant as it is before MMP. Also recoveries of dead and live oils at same pressure show different values due to differences in miscibility condition of injected gas. Then as the graphs demonstrate, relative permeability reduction due to hysteresis effect has dominant effect on pressure drop curves. Finally, as the production rate curves show, nearly all of the remained oil after breakthrough is produced as the gas is being produced and almost no oil can be recovered during water production portions.