Abstract
This paper reports on experimental work focused on modifying choke design with the aim of reducing oil droplet break-up in the choke in high water-cut production wells. Producing oil under such conditions, with the oil dispersed in the produced water, leads to severe break-up of the dispersed oil droplets. This break-up is caused by high energy dissipation in the choke. Previous work carried out in Delft indicated that, under identical process circumstances (tubing diameter, flow-rate, pressure drop, oil type and concentration), the break-up process is significantly influenced by the choke geometry. In this work we discuss possible ways of modifying the choke geometry to reduce droplet break-up. Three model chokes were tested in the laboratory: an orifice, a small choke consisting of 7 parallel tubes and a larger choke consisting of 13 parallel tubes. These chokes were tested at identical flow rates and with the same pressure drop across the chokes. The larger model choke was the superior one in the sense that in this device the least break-up of oil droplets took place. In the small model choke more break-up occurred, while the most severe break-up was observed for the circular orifice. A general conclusion of the investigation is that the intensity of the break-up process occurring in the (model) choke can be considerably reduced by adaptation of the choke design. A choke design based on parallel tubes gives opportunities for improving the choke performance with regard to oil droplet break-up, while still making it possible to vary and control the volume flow-rate as with a conventional choke.
This investigation suggests that it will be possible to construct chokes with improved characteristics with regard to oil-droplet break-up in high water-cut wells. This will result in easier separation and less emulsion-forming downstream of the choke.
