Light beam reflectance measurement of droplets diameter distribution in crude oil emulsions

Author(s): 
Simone Less, Regis Vilagines (R&D Center, R&D Division, Saudi Arabia, Saudi Aramco)

Stable oil field emulsions create challenging conditions in the petroleum production industry. One important characteristic affecting the stability and rheology of emulsions is the Droplet Diameter Distribution
(DDD).


Sketch of the FBRM probe

A few techniques are available to determine the DDD in clear and dark liquid/liquid mixtures. Most of them, like the traditional light scattering techniques, require sampling and dilution. Dilution can affect the droplets coalescence rate, and consequently, change the DDD by altering the solubility state of components responsible for emulsion interface properties. Moreover, the samples obtained may not be representative of the actual process conditions once depressurized to ambient for observation. Focused Beam Reflectance Measurements (FBRMs) were conducted on suspensions mimicking the optical properties of emulsion systems, with the goal of optimizing the instrumental settings. Then, the same technique was applied to water-i n-crude oil and crude oil-in-water emulsions to evaluate its accuracy. An algorithm was developed to compute the diameter distribution in populations of spherical droplets from the chord length distributions measurement data. The greatest advantage of this technique is the ability to perform a real-time, in situ measurement of DDD at actual process conditions. The method is capable of repeatable measurements of droplet diameter distributions; however, the measurements are limited within a range of droplet sizes, and the results are sensitive to the relative optical properties of the continuous and dispersed phases, making the calibration step a fundamental phase of the measurement protocol.