Effect of the Addition of Low Molecular Weight Alcohols on Heavy Oil Recovery during Alkaline Flooding

This study presents an experimental study, including interfacial tension (IFT) measurements, sandpack flood tests, and microscopic studies, for investigating the effect of the addition of low molecular weight alcohols on heavy oil recovery during alkaline flooding. According to the IFT results, the addition of low molecular weight alcohols can be detrimental to IFT reduction for the alkaline/heavy oil system, due to the partitioning of the alcohol molecules at the oil–water interface reducing the interfacial space available for surfactant molecules. However, sandpack floods conducted with the addition of the low molecular weight alcohols show a marked improvement in oil recovery over the alkaline-only flooding. The incremental oil recovery increases with the alcohol chain length from methanol to n-pentanol, but for the less water-soluble isoamyl alcohol and n-hexanol, the incremental oil recovery starts to decrease. The microscopic studies indicate that the alcohol additives can accelerate the reaction rate to produce large amounts of small water droplets inside the oil phase (W/O droplet flow), which reinforces the Jamin effect to improve sweep efficiency. Meanwhile, the addition of low molecular weight alcohols can also lead to the reduction in water-in-oil (W/O) emulsion viscosity, which contributes to the mobilization of trapped W/O emulsions, thereby improving the displacement efficiency of the alkaline flooding process.