Photomicrographic droplet size

A very careful study of the kinetics of coalescence of an oil/water emulsion using photomicrographic droplet size analysis was done by Lawrence and Mills (17). They prepared their emulsions by homogenization. Their technique was recently modified by us to determine emulsion stability in petroleum sulfonate systems of interest in chemically enhanced oil recovery processes. These observations are given elsewhere ( , 7). ... 

Drop stabilization methods rely on the immediate stabilization of drops by encapsulation with thin polymer films or surfactants [219-221] a photomicrographic method has been employed usually after encapsulation of drops. However this method cannot always be used due to incompatibility of the encapsulating materials with some systems. The method also has the disadvantage of the influence of the chemical treatment on drop size. A special sampling apparatus has been developed to withdraw a sample of dispersed phase from the mixing vessel to stabilize drops with a surfactant and to force the dispersed sample through a capillary with a photometer assembly to measure both droplet size and concentration [222]. 

Figure 5 is a photomicrograph (250 x ) of an acid-in-diesel emulsion. The average droplet size for this acid-in-diesel emulsion is nearly 77 pm [14]. Excellent field results were claimed when this acid was used to stimulate carbonate formations with permeability less than 100 mD [14,15]. 

Figure 9.1 Photomicrographs of 1,2-dichloroethane droplets as a function of time, (a) Double exposure on the same frame, with the image to the left at time zero and the image to the right at 300 s later, (b-d) Time evolution of droplet sizes with image (b) taken at time zero, (c) 900 s later, (d) 3600 s later (Reproduced by permission of Academic Press from ref 7)...

Figure 19. Reflected-light photomicrograph of the same field of view as Figure 18 in the fluorescence mode showing bright oil droplets in a dark water-continuous phase. In this photograph the clays cannot he seen. This type of image with high contrast between the phases is ideal for automated analysis. However, droplets not exactly in focus (O) may be incorrectly sized.

Figure 21. White-light (top) and blue-light fluorescence mode (bottom) photomicrographs of a water-in-oil emulsion. With white light the water droplets have internal reactions that lead to a halo effect and an incorrect size estimate. With incident blue—violet light to excite oil-phase fluorescence, the emulsified water droplets appear as dark circles in a bright oil background and are significantly easier to size. However, droplets that are above or below the plane of focus will still be incorrectly sized.

Figure 9. White-light (polarized) photomicrograph in reflectance mode of a clay suspension with significant oil content. With polarized light, the clays (C) appear bright and the oil droplets cannot be seen at all. On the left is the same field of view but in fluorescence mode in which only the organic components can be seen. With conventional optical images, features above or below the focal plane will appear as points of light or have halos that prevent accurate sizing. (Adapted from reference 19. Copyright 1992.)...

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