Analysis of Microscopic Displacement Mechanisms of Alkaline Flooding for Enhanced Heavy-Oil Recovery

In this study, the microscopic displacement mechanisms of alkaline flooding for enhanced heavy-oil recovery are investigated using a micromodel. It has been observed that alkaline flooding exhibits a better sweep efficiency than waterflooding, and the serious viscous fingering is significantly reduced. The main microscopic mechanisms of alkaline flooding for enhanced heavy-oil recovery are that the alkaline solution penetrates in crude oil and water drops are, subsequently, formed inside the oil phase, which can improve the mobility ratio and, thus, lead to the improvement of sweep efficiency. The higher the alkaline concentration, the more easily the alkaline solution penetrates in the oil phase. Therefore, a greater improvement in sweep efficiency can be obtained using a higher concentration of alkali. The primary mechanism of the formation of the water drop inside the oil phase during alkaline flooding is related to the interfacial interaction between alkali and heavy oil, which not only results in the drastic reduction of oil water interfacial tension but also leads to the non-uniform enrichment of in situ surfactants activated by alkali.