AC field induced destabilization of water-in-oil emulsions based on North Sea acidic crude oil

•Viscosity drop and separation of water-in-crude oil emulsions.•Droplet collision frequency enhanced by the shear movement.•Combined effect of flow regime and voltage.•High frequencies do not initiate drop deformation and breakage. The current work explores the effects of alternating current (AC) electric fields on coalescence of water droplets in crude oil. A North Sea crude oil emulsion with aqueous phase volume fraction of 0.3 and ∼2μm water droplets was used. The emulsions were prepared by an Ultra-Turrax disperser. Volume-specific energy input (Ev) has been calculated. Droplet collision frequency was enhanced by increasing the shear rate and initiating intense flow conditions. The flow conditions were verified to be within the valid flow regime for the specific rheometer geometry through calculations of the Taylor and Reynolds numbers. Viscosity alteration of water-in-oil emulsions as a result of electrocoalescence was investigated under the influence of electric fields in conjunction with variation of temperature, frequency, electric waveform, and duration of the applied electric field.