Effects of solvent composition and test temperature on the stability of water-in-model waxy crude oil emulsions

In this article, we investigated the influence of solvent composition and test temperature on the stability of the water-in-oil model emulsions through asphaltene dispersion stability, wax precipitation characteristics, rheology, interfacial film characteristics measurements of diluted model oil-simulated formation water, emulsion stability, microscopic observations, and molecular dynamics simulation. Specifically, we examined the stability of crude oil emulsions at 15 degrees below and 30 above WAT using model oils containing 0.5 wt% asphaltenes and 10 wt% paraffin wax having varying solvent compositions. We observed that increasing the amount of liquid paraffin in the solvents led to smaller changes in the WAT, a reduction in the cumulative wax crystal at-20 degrees C, and a change in the form of wax crystals from fine particles to larger agglomerated wax crystals. However, the asphaltenes dispersion stability decreased along with it, rheology continued to improve. Meanwhile, we innovatively validated this experimental result using molecular dynamics simulations. Test temperature significantly affects emulsion stability. At 30 degrees C, increasing the percentage of liquid paraffin reduces interfacial tension, in-creases the dilatational modulus, and enhances the durability of the interfacial film. This contributes to form small droplets and increases emulsion stability. At 15 degrees C, increasing the liquid paraffin percentage promoted the development of a more structured wax crystals network, which significantly enhances emulsion stability by binding water droplets. Additionally, we observed that a wax crystal interfacial film could be developed from the wax crystals on the surface of emulsified drops, which improves the emulsion stability and interfacial film strength. Based on our findings, we innovatively present an influencing mechanism model of solvent composition on the synergistic stabilization of model oil emulsion using asphaltenes and paraffin wax.