Many production chemicals are complex mixtures of surfactants yet are described by a single partition characteristic such oil soluble or water soluble. This paper presents a simple model of multi-component surfactant mixture partitioning based on the work of Zhu and Free. The model is extended to show how the composition of the production chemical changes as the oil/water ratio changes. The results show that the composition of the original production chemical in either the oil or water phases is rarely the same as the neat product on injection and can vary substantially as the water-cut changes over the production life and through the production system.


Production chemicals used in the oil and gas industry are often multi-component surfactants which will partition between the oil and water often with different partition coefficients. As a consequence of the different partition coefficients, the proportion of each component in either the oil phase or the water phase will change as the water cut changes. A simple model has been developed to illustrate the compositional changes in the oil and water phase over the water-cut range.

The model is an extension of the work of Zhu and Free, and clearly shows how the ratio of the components in either the oil or water phases rarely matches the composition ratio in the neat product.1 As a result, if the performance of a production chemical is tested in a single phase e.g. corrosion inhibitor testing in brine only, the composition ratio of the components is unlikely to reflect what will be found under field application.

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