NORWAY:

Submersible mixer aids mud recycling

The recycling of drilling fluids is saving oil companies in Norway big money while avoiding environmental problems. In fact, recycled drilling fluids have lowered disposal costs by as much as 80%, says Frank Mueller, environmental supervisor for the fluid engineering company Swaco, a subsidiary of M-I L.L.C.

Typical North Sea oil-based mud costs range from $645 to $1,290 per ton. And in the past, the mud could be used only once, and then it had to be discarded because of contamination by water and drill cuttings. However, Swaco’s patented recycling procedure, launched last spring, lets companies re-use expensive mud.

Through a special process involving large mixing and storage tanks, pumps and shear units, solid contaminants and water are removed from the used drilling mud. Using this technique, as much as 80% of drilling mud can be recycled. For oil companies, that means big savings.

The stainless steel submersible mixer is a low-energy consumption unit with a jet ring to increase mixing efficiency. It can be secured in any position, ensuring optimum mud mixing in even the most irregularly shaped tanks.

Submersible mixers from ITT Flygt of Emmaboda, Sweden, are key to the recycling process. "We chose submersible mixers because of their advantages for mixing fluids, being moveable and capable of being directed," says Mueller. Traditional vertical mixers did not mix adequately, meaning that the recycling process took longer, required more additives and resulted in sedimentation problems. When sedimentation collects on the bottom of the tanks, they have to be emptied and cleaned frequently.

Mounted inside the mud tanks, submersible mixers prevent build-up of sediment by creating a bulk flow that mixes the entire tank contents. Better mixing also means shorter batch times and fewer additives.

In 1999, ITT Flygt received the professional stamp of approval – American Bureau of Shipping (ABS) certification – for its submersible mixer. The ABS Guide for Certification of Drilling Systems draws on requirements from industry standards and codes.

This article was adapted from Impeller, a newsmagazine from ITT Flygt.