The new system will remove high concentrations of free oil from the water stream with the dissolved gas flotation (DGF) method from Siemens, so the water can be used for subsurface re-injection. The capacity will be 850,000 barrels of water per day (BWPD) and the project is scheduled to begin operation by mid 2008.
According to Siemens, produced water treatment plants are used around the world to meet discharge and injection water quality standards set by governing bodies of the respective countries. Saudi Aramco uses injected water to maintain reservoir pressure to maximise oil production. Presently, the system handles Arab heavy crude oil and formation water from the Safaniya oil field and Arab Medium crude oil from Zuluf oilfields. The formation water from both fields is processed and then re-injected.
Produced water treatment systems using Monosep dissolved gas flotation (DGF) pump technology from Siemens allows for the separation of oil from water. The equipment is said to occupy a smaller footprint than comparable flotation technologies.
Siemens Water Technologies provides the plant with produced water treatment systems which consist of vessels using the proprietary DGF pump technology. The DGF pump is the heart of the system and works by using a dual sided impeller that pulls water and gas into the pump volute.
The backside of the impeller has a “sub-atmospheric” zone that pulls vapour from the blanket gas source or other means and allows mixing with the incoming fluid. As this mixing occurs, the vapour is dissolved into the water creating micro-fine bubbles that break out of solution once a pressure drop is experienced. This pressure drop occurs once the fluids and dissolved gas are flowed across a globe valve prior to entrance into the flotation vessel.
Due to the close tolerance between the back vanes of the impeller and the back plate of the DGF pump, the vapour is sheared into micro-fine bubbles piped into a vessel or tank allowing the fine gas bubbles to attach to the oil droplets. As the gas bubble attaches to the oil droplet, the droplet floats to the surface at an accelerated rate.