In Dukhan oil production facilities, the well output is a mixture of oil, gas and water. Gas is released naturally as pressure decreases through the stages of the process. Separating oil and water is much more difficult, especially during low temperature due to the tight emulsion caused by fluid viscosity increase in spite of the demulsifier injection experienced mainly in winter time. Water droplets are dispersed forming water-oil emulsions which can be extremely stable due to surface tension and particles attaching themselves to the water-oil interface. Typically, a multi stage separation process is employed. The first stage separation vessel is one of the largest pieces of equipment on the plant. In many cases, it is time consuming to achieve the optimum oil-water separation output and requires an injection of a large amount of chemicals (demulsifier) to improve the separation efficiency.
Applying the electro coalescence technique in the first stage of separation process increases the efficiency of the separation process. This technique has been developed and is now established. This has led to a modular device known as a Vessel Internal Electrostatic Coalescer (VIEC). The VIEC is expected to reduce such phenomena by increasing the residence time and reducing the troublesome emulsion layer in the first stage separator by due to its coalescing effect hence reduced the required injection of demulsifier. The application of electrostatic force to break oil-water emulsions and increase water droplet size is an old and proven technology. A coalescer forces small water droplets to merge and form larger and thus faster sedimenting drops. Therefore, the settling velocity of water droplets in oil not only depends on viscosity and density, but also on the droplet radius squared. If the average droplet size is doubled, separation time decreases by a factor of four. Increasing droplet size is exactly what an electrocoalescer does. This means that in many cases, such as in an existing separator, production can be increased by as much as 50%.
This paper highlights first the theory of the VIEC technology. Then moves to discuss the consequences might be faced, the main features of VIEC technology. Finally shows the results of testing the new technology at different rates of chemical injection.