SIEMENS

The deep sea is a remote and forbidding place. It’s cold and dark. Blind, pale crabs skitter across the sea floor and ghostly transparent fish float through the water, thousands of meters below the surface. At these depths the water pressure is immense, amounting to several hundred bar. Slowly but surely, mankind is advancing into this realm, because large deposits of oil and natural gas can be found beneath the sea floor. The International Energy Agency estimates that global energy demand will increase by at least one third between now and 2035, with growth primarily being driven by developments in China and other emerging markets. Renewable sources of energy alone are not expected to be able to cover this demand.

As oil and gas reserves dwindle on land, interest in the deep sea is steadily increasing. In 2007, 1.4 billion tons of oil were pumped up by offshore facilities worldwide, accounting for a relatively large share of about 37 percent of total annual output.

The situation is similar for natural gas. Most offshore facilities are located in comparatively shallow waters such as the North Sea, where the average depth is just under 100 meters. But the oil and gas industry is gradually venturing into deeper and deeper waters.

Most subsea deposits are still extracted from the surface. Compressors and pumps on the decks of platforms and drill ships press oil and natural gas out of reservoirs and pump it up from the sea floor through kilometer-long pipes. After reaching the surface, the fuel is cleaned and processed.

But according to experts it would be much more profitable and safer if the extraction systems were not located on drilling rigs and platforms that are susceptible to storms, but instead directly on the sea floor. Not only could deposits be exploited more easily if pumps and compressors were located closer to boreholes; the mixture of oil, sand, and water could also be cleaned and processed at the source.

In addition, such subsea installations would not only require less extraction technology than do surface platforms but could cover a larger area. A drilling rig has a limited radius in which it can extract fuel. If all its associated pumps and compressors were located on the sea floor instead, oil could be pumped out by a central extraction system (known as a “Christmas tree”) from numerous boreholes in a wide radius and then pumped up to the surface. Such a system would reduce the number of pumping stations required and therefore significantly lower the risk of leaks. The processing of oil and gas in the deep sea already generates slightly more than $20 billion in sales, and Siemens estimates that this market could double by 2020.

A Grid for the Sea Floor. “As specialists for power supply and transmission systems, we are in the process of developing a complete subsea power grid with which subsea processing equipment can be controlled and supplied with electricity,” says Atle Strømme, Senior Vice President and Head of Subsea Solutions at Siemens Energy.

Siemens also plans to supply compressors suited for deep sea use. In such a deep sea electricity supply system, all of the electrical devices for controlling pumps and compressors would be located close to one another right on the sea floor. The facility would then be much easier to assemble and maintain, and therefore less costly as well. Such a system would primarily include transformers, frequency converters, and switchgear.

Although such a complete subsea system is not yet fully developed, Siemens has already supplied individual components for underwater applications. For example, since the late 1990s Siemens has, supplied transformers for use at a depth of 1,000 meters off the Brazilian coast. However, power supply systems are still generally found on platforms or on land, depending on the location of the oil and gas deposits. Only a few components are installed on the sea floor. However, compact facilities on the sea floor would have substantial advantages, since they would require only a single supply line to transmit electricity to the area in question. “Components would be attached to a common template on the sea floor,” says Strømme’s colleague Bjørn Einar Brath, Senior Vice President at Siemens Energy. “They could then be centrally monitored and supplied with electricity.”

With the help of an optical data cable, a subsea facility could also be operated and controlled from a service station on land. In addition, the cable could be used to transmit data from numerous surveillance sensors, enabling high-tech equipment to continuously monitor the system. “The template concept would be very beneficial in terms of maintenance,” says Brath. “In such a situation, deep sea robots could safely disassemble individual components on the standard template.”

Over the next few years Siemens plans to develop a subsea grid to prepare it for everyday use. The first practical test of a complete system is scheduled to begin by early 2013, with full commercial availability planned for 2014. Until then, the main task will be to properly seal components against water intrusion and protect them against the tremendous pressures found on ocean floors.

With this in mind, Siemens has entered into a partnership with energy companies Statoil and Chevron to produce a deep sea frequency converter to supply oil pumps and gas compressors with exactly the right operating voltage. The new converter’s housing is filled with oil to offset the water pressure.

Frequency converters and other components are usually installed in casings on land before they are lowered into the water. Although this approach works well in shallow seas, a conventional air-filled container has to be very large to withstand the pressures at a depth of several thousand meters. By contrast, a frequency converter within an oil-filled housing is much easier to handle.

The Deepwater Market. Because Siemens regards deep sea production as a promising market, it recently acquired Bennex and Poseidon, two medium-sized Norwegian subsea companies. Bennex, which is based in Bergen, has specialized in manufacturing electrical components, cables, and connections for use at great depths. Poseidon, which has its headquarters in Stavanger, is an engineering company that specializes in subsea assignments. Among other things, it modifies technologies for a range of underwater applications.

The companies are now working together to plan a subsea grid in detail. And far more is at stake than just big components. At great depths, after all, even minor details can make a huge difference. Experts from Bennex are highly skilled in developing solutions for deep sea environments. Their company’s pro- duct range includes water tight titanium connections, durable power cables with a copper core, glass-fiber reinforced epoxy casings, and doubly secured contacts with rubber seals and protective covers made of stainless steel.

But even a power electrical supply system is not enough to extract raw materials. That’s why Siemens also offers a very robust compressor for transporting gas. Known as the STC-ECO, the device was initially conceived for use on land. Since 2006, however, it has been used to pump natural gas from a field in the Netherlands into the country’s supply network. The fact that the machine doesn’t need any seals makes it ideal for use in the deep sea. The Unlike conventional compressors, where the drive motor and the natural gas compressor are separate, STC-ECO’s key components are located in the same capsule, The motor is usually connected to the compressor housing by a drive shaft. As a result, the location where the shaft penetrates the housing has to be reliably sealed. The STC-ECO, by contrast, doesn’t need any seals and is therefore ideally suited for deep sea use.

“High reliability is essential underwater,” says Brath. Repairs require special ships, which are extremely expensive. Components therefore must be able to operate nonstop and without any defects. The STC-ECO, for example, is designed to operate under water around the clock for at least five years without any maintenance.

The system operated by Siemens in the Netherlands already meets these requirements. And it has another feature that makes it ideal for deep sea operation: Its bearings do not need lubrication with oil. This is important, because an oil change is impossible on the sea floor. Instead, the system uses electrically excited magnetic bearings in which the shaft effectively “floats.” Improvements in the reliability of the bearings’ electrical control are now planned, so that subsea operation will become even more reliable. In addition, touchdown bearings made of small ceramic balls that catch the shaft in the event that the magnetic control fails are also to be further optimized. The complete system will thus be subjected to even more intensive stress tests before it can commence its long-term work underwater. It will take at least three years of testing before the system is ready for deep sea use.

Oil extraction at great depths is of course more expensive than comparable operations on land. However, subsea facilities can improve the exploitation of gas and oil fields, thus substantially increasing profits and reducing costs. That’s reason enough to expand the company’s research activities in this field as well. Siemens has established partnerships with government research institutes in Singapore and Brazil and has also set up its own labs in Houston, Texas, and Trondheim, Norway. “We are not only focusing on the technology,” says Strømme. “Training is also a major concern. After all, only a few engineers worldwide currently specialize in subsea applications.”