Measurement and Calibration of Droplet Size Distributions in Water-in-Oil Emulsions by Particle Video Microscope and a Focused Beam Reflectance Method

Water droplet sizes in crude oil emulsions were measured using an in situ particle video microscope (PVM) probe and a focused beam reflectance measurement (FBRM) probe for a variety of oils spanning over two orders of magnitude in viscosity and for varying shear rates. The arithmetic or Sauter mean diameter was found to maintain the same constants of proportionality with the maximum (99th percentile) droplet size for different distributions, previously only shown for water-continuous emulsions. The FBRM values for the mean droplet size, while lower than the PVM values, could be related to the latter by an empirical quadratic relationship with an average error of less than 20%. The droplet size distribution was found to be represented well by a log-normal distribution with good agreement between correlated and measured mean droplet size. Following the agreement between the mean and maximum droplet sizes, the log-normal standard deviation was linearly related to the mean droplet size. The PVM probe was found to be a useful tool for determining droplet sizes in water-in-oil emulsions and as a calibration method for the FBRM probe. The droplet sizes measured provide a useful set of data for comparison with predictive models to determine the mean size or full droplet size distributions.