Rheology of gel-containing water-in-crude oil emulsions

Abstract

The rheological properties of gel-containing emulsions have been studied. Emulsions have been obtained from well production facilities after the use of demulsifiers based on oxyethylated high molecular weight surfactants. Today the properties of such emulsions are poorly understood, they are practically not destroyable by commonly used methods and ranked as oil waste. The studied emulsions were highly flocculated water-in-oil emulsions with aqueous phase concentrations of 53–62 wt% and “gel” contents of 8–25 wt%. The average diameter of water droplets varied from 40 to 50 μm. The gel-like behaviour of the studied emulsions has been confirmed by the dynamic rheological analysis using oscillatory techniques at 20 and 60 °C. The storage modulus G′ was higher than loss modulus G″ in a wide range of frequencies without a crossover. The gel-containing emulsions demonstrated the characteristics of non-Newtonian flow of the pseudoplastic type at 20 and 60 °C. Besides that, the emulsion with “gel” content of 25 wt% exhibited higher viscosity at 60 °C than at 20 °C due to the dehydration of oxyethylated surfactant molecules and additional stabilization of the water-in-oil emulsion. The rheological behaviour of the studied emulsions has been approximated by the Bingham model. The yield strength increased sharply with an increase in the “gel” concentrations because the “gel” networks in these emulsions were stronger. The results of rotational and oscillatory tests carried out at different “gel” concentrations, temperatures and shear rates can be useful in understanding and predicting their subsequent processing and demulsification.