Experimental Investigation of Wettability Effect on Co-Solvent Flooding of Heavy Oil Reservoirs

Despite numerous experimental studies there is a lack of fundamental understanding on how the chemical composition of a co-solvent at different wettability conditions might affect heavy oil recovery efficiency in 5-spot models. In this work a series of solvent injection experiments performed on a one-quarter five spot glass micromodel. Four groups of commercial chemicals as well as their mixtures as co-solvents were added to one light hydrocarbon solvent. New chemical procedures were applied to alter the wettability of micromodel towards strongly water-wet and oil-wet conditions. Precise analyses of the pictures provided continuously during injection processes were used to explore the solvents' displacement efficiency. It has been observed that different groups of chemicals have various effects on oil recovery based on their nature. An optimum mixture of co-solvents with greatest sweep efficiency was determined. The observations confirmed that the presence of connate water in strongly water-wet medium could improve the final recovery, while the effect of wettability in absence of connate water is at minimum. It was found that the displacement efficiency of the solvents depends on the surface wettability condition and is generally higher in strongly water-wet medium.