Patented oil washing on Martin Linge
A new patented wash tank technology benefits the environment as well as operations on the Martin Linge Platform, when it is implemented for the first time in the North Sea.
Stig Helland, Senior Project Engineer for the FSO package on Martin Linge
Oil and water will be transported to an FSO for further processing.
Through a desalination process water and salt are removed from the oil.
The Martin Linge field mainly delivers gas, but also some oil. The oil has high salinity and must be processed before it can be transported from the field. Consequently, the oil and water are separated from the gas on the platform and piped to an FSO (Floating, Storage, Offloading vessel) located about 3.5 kilometres from the platform.
The new separation technology will be installed on the FSO. When the oil and water arrive on the FSO, it is routed into two parallel washing systems that are completely the same. Each system has two large tanks that the oil will pass through. The size of the tanks is approximately 8 500 m3 per tank.
“It is very exciting that this technology is in place on the Norwegian shelf for the first time. One novelty is that the oil washing equipment will function well even in high waves in the North Sea. This is a patented process from Total,” says Stig Helland, Senior Project Engineer for the FSO package on Martin Linge.
Oil separates from water
First, the oil is separated from the saltwater. This takes place in a process similar to a reverse sprinkler system. The oil and water are projected through a number of small holes in pipes near the bottom of the tank. This causes the oil to raise slowly towards the surface through a layer of water at the bottom of the tank. On its way up, the oil droplets coalesce, causing the oil to form a layer on top of the water. Simultaneously, the water droplets that accompany the oil will also coalesce and sink towards the bottom of the tank.
Helland explains that when the oil is routed to the next tank, the process is repeated, but this time freshwater is added and mixed with the oil. This freshwater dilutes the remaining saltwater and the water is again separated from the oil in the wash tank. Thus, the salt content is reduced, and the result is high-quality oil.
Saves weight and costs
"There are two smart advantages with this wash tank technology," Helland says.
"Firstly, the weight of and amount of equipment on the Martin Linge platform are reduced, as the oil is cleaned on the FSO, not on the platform itself. The jacket would have to be designed for a lot more weight. By using the wash tank technology, we save both money and equipment.”
Secondly, the process does not result in environmental discharges. The processed water that remains after the oil has passed through the wash tanks, is returned to the reservoir near the oil recovery site.
"The water is almost clean, and redirecting it to the reservoir will have no impact on life in the sea or other places," Helland says.