Effect of silica and clay minerals on rheology of heavy crude oil emulsions

Researchers studying oil-in-water emulsions practically always deal with the oil and water purified of mineral admixtures. In reality, a water/crude oil emulsion obtained from a well contains solid clay-and sand particles, which may act as surfactants. In the present work, the solid particles' effect on the morphology and rheological behavior of heavy crude oil emulsions are studied. Water-in-oil emulsions are fluids with the weakly non-Newtonian behavior and viscosity exceeding that of the crude oil. Solid particle admixtures have practically no effect on the viscosity of these emulsions. Oil-in-water emulsions, on the contrary, are viscoplastic systems, the yield stress of which increases with silica-and clay admixture content. The transition from water emulsions to the oil ones was realized using surfactants (cetrimonium bromide, sodium dodecyl sulfate, Tween 85, and Triton X-100), the success of the phase inversion depending on the hydrophilic-lipophilic balance of a surfactant. The effective viscosity of the oil-in-water emulsions is demonstrated to depend on the shear rate and solid particle- and surfactant concentrations, this providing the opportunity to optimize the compositions of crude oil emulsions for transportation.