Electrocoalescence - Criteria for an efficient process in real crude oil systems

The fundamental mechanism active in the electrocoalescence process has been identified as a formation of an electrohydrodynamical surface instability. Hydrodynamic models for drop movement has been established and verified experimentally in model systems. This far, coalescence has been studied using transparent model oils. The challenge is to link this knowledge to realistic conditions and water-in-oil emulsions. Several oil companies and equipment manufacturers have a specific crude oils where the emulsi ons may be stabilzed by e.g. particles, asphaltenes and acids. Heavy crudes will be given special attention. The project is divided in three: 1 - Coalescence criteria will be studied in real oils. Surface behaviour will be investigated using electric exci tation of singular drops in order to study how a real surface influences the formation of the coalescence instability. Critical field for flocculation and coalescence will be studied using e.g. a test cell developed by Sjøblom et al.. NIR techniques for i maging drops in dark oils will be needed. 2 - Intrumentation for measuring coalescer efficiency on real oils will be developed based on e.g. rheometers with electric field applied or using other types of configurations where liquid flow, voltage and tempe rature may be varied. This will be combined with pressurized emulsions to make it realistic for subsea and downhole conditions. Dielectric response and acoustic spectroscopy will be used to investigate sedimentation speed in dark emulsions. 3 - Hydrodynam ic models will be developed, where viscosity and surface conditions of drops may be taken into consideration. Also, electrostatic models for emulsions with higher water cuts will be investigated to find possibilities and limitations for CFD-based design t ools for equipment.