Research on viscoelastic properties of water in waxy crude oil emulsion gels with the effect of droplet size and distribution

Abstract

AbstractThe viscoelastic properties of gelled oil can reflect its structural characteristics, which are significant for the restart operation of prolonged‐shutdown pipelines. The viscoelastic properties of water‐in‐oil (W/O) emulsions are more complicated on account of the influence from the dispersed water phase, which cannot be ignored. This paper attempts to reveal the relationship of viscoelastic characteristics to temperature and water fraction for waxy crude emulsion gels from a micro perspective. As a basis of the rheological analysis, the droplet size and distribution of inner phase are studied with microscopic observation. It is found that both the total number and Sauter mean diameter of dispersed droplets increase with growth of the water fraction. Through a series of small amplitude oscillatory shear experiments, the linear viscoelastic regions and the viscoelastic parameters of emulsion gels with different water fractions are obtained and compared under varying temperatures. The results provide evidence that as the water fraction rises, the structural strength of emulsion gels becomes stronger. This can mainly be attributed to the larger deformable oil‐water interface area with adsorbed wax crystals and the stronger interactions among water droplets. Based on the experimental results, regression formulas for viscoelastic parameters, including elastic modulus, loss modulus, and loss angle, are proposed and proven reliable. This offers useful information for the restart operation of oil‐water multiphase transportation pipelines.