Rheological properties of heavy oil emulsions with different morphologies

Abstract

Morphology and rheological properties of emulsions produced from heavy oil and aqueous solutions of surfactants with high hydrophilic-lipophilic balance (HLB) varying from 11 to 40 have been studied. The initial oil containing only trace amounts of water showed Newtonian properties over a wide temperature range (20–70°C). As a function of preparing conditions, surfactant HLB and amount of aqueous solution, stable emulsions with different morphologies were formed: water/oil (W/O), double water1/oil/water2 (W1/O/W2) and oil1/water/oil2 (O1/W/O2), as well as multiple emulsions having more complicated morphology. Structural diversity of the emulsions determines the scatter of their rheological properties from Newtonian to visco-plastic. Introduction of aqueous solutions of surfactants with HLB ≥15 (Tween 80 and sodium dodecyl sulfate) gives rise to multiple emulsions characterized by a specific structure: ultradisperse W/O emulsion permeated with channels consisting of double W1/O/W2 emulsions. Such multiple emulsions containing 15–25vol% of surfactant aqueous solution exhibit non-Newtonian properties. Their effective viscosity at the shear rates typical for the oil flow regime in pipelines is reduced by 10–50 times as compared with the viscosity of the initial crude oil, being therefore acceptable for transportation.