Transforming power 3000 meters under the sea

How subsea transformer technology helps active oil and gas wells to be productive for longer periods of time

Offshore technology now makes it economically feasible to pump oil and gas from underwater fields once considered too difficult or remote to be developed. Oil is boosted and gas compressed to move in larger volumes to increase production. Alternatively seawater or gas is pumped into a well to increase pressure and force the remaining oil or gas trapped in reservoirs under the seabed to the surface. This keeps active wells productive longer, and helps open up new deepwater fields.

Large quantities of power required for such processes, is generally transmitted through subsea cables at high voltage levels. On the floor of the sea, transformers reduce the high voltage to levels that can be used by motors of pumps and compressors, so it is critically important to have reliable equipment powering the process. As offshore sites can be at depths of several kilometers, hundreds of kilometers (km) from the mainland, these transformers need to be specially designed and fabricated to overcome challenges like extreme temperatures and pressure, saltwater corrosion and overheating, while providing safe and reliable performance as well as cost benefits. Reliability is essential, as maintenance is almost impossible at those depths, and bringing equipment to the surface for repair is expensive

ABB pioneered subsea transformer technology and has more than 15 such installations currently in operation. A 70 MVA (megavolt ampere) unit is being designed and verified for the deepwater Ormen Lange gas field, 150 km off the Norwegian coast. It will operate one kilometer below the surface, feeding power to compressors on the seabed to improve gas production at Ormen Lange, which supplies around 20 percent of the UK’s natural gas needs.

As well as making wells more productive over longer periods of time and helping to discover new sub sea oil fields ABB subsea transformers power equipment such as boosters, pumps, compressors, pipeline heating systems, electrical distribution systems, frequency converters and wave hubs.