The coalescence of water droplets dispersed in a heavy-oil has been investigated under fluid dynamic shear and gravity. Emulsions with different surfactant (SPAN 80) loadings are considered, with the upper concentration in excess of the critical micelle concentration (cmc). A controlled stress rheometer (TA Instruments AR2000ex) is used to study the influence of fluid dynamic shear on droplet size coarsening whilst a closed loop vertical settling column is used to study droplet coarsening under gravity separation. With a surfactant loading below or equal to the cmc, the droplet size distribution is observed to increase under certain flow conditions, a direct result of drop-drop coalescence in the flow. For gravity separation, the trends in droplet coarsening are a little less conclusive. Generally, it is observed that there is little or no coalescence in either the sedimentation or packed bed settling zones. This indicates that the low shear conditions and the hydrostatic head loading are both insufficient to initiate droplet coarsening.

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