Thin liquid film technique — application to water–oil–water bitumen emulsion films

We describe an adaptation of the thin liquid film-pressure balance technique (TLF-PBT) for a systematic study of water/diluted-bitumen/water thin films. Recent research into the stability of water-in-oil emulsions, particularly those occurring in the oil industry, has not properly addressed the dependence of the emulsion stability on the thin films that are formed between approaching water droplets. The objective of this study is to obtain some insight into the mechanisms that stabilize the emulsion with particular attention to the relative importance of the resin, asphaltene, and solids fractions of the bitumen. Measurements of film lifetime and equivalent thickness indicated that the behavior of the film strongly depended on the type and concentration of solvent used to dilute the bitumen. Toluene-diluted-bitumen films drained continuously until a stable, uniform grey film was formed. Heptane-diluted-bitumen films formed black films covered with a scatter of small white dimples containing trapped liquid except at heptane:bitumen weight ratios of 10:1–15:1, where a network of fine white spots of unknown origin was formed. While the asphaltene and resin fractions alone provide a partially stable film, the combination of resin and asphaltene produced extremely stable films, a result that agrees well with emulsion studies by other researchers.