Pictures of the Future        Fall 2008

An Ocean of Opportunity

About one fourth of all known oil reserves are beneath the sea floor. Tapping these remote deposits is an extremely complex and costly endeavor. Oil companies must drill kilometers beneath the seabed, while coping with gale-force winds and  stormy seas. Technologies from Siemens play a key role in enhancing safety and reducing costs on offshore platforms and drilling ships.

Those were truly the good old days. In August 1859, in Oil Creek, Pennsylvania, oil industry pioneer Colonel Edwin L. Drake had to drill to a grand total of only 21 meters and 20 cm before hitting "black gold."

A year prior to Drake’s breakthrough, oil had been successfully extracted near Celle in northern Germany, after the thick liquid had seeped through to the surface on its own. And in the 15th century, monks on the shore of the Tegernsee, a lake in southern Bavaria, enjoyed similarly easy access to the coveted substance—simply taking their "Saint Quirin oil," which was used for medicinal purposes, from a source above ground.

Today, billions of dollars are spent in the search for new oil deposits, which can take years or even decades to develop. This is because the vast majority of oil reserves are found between 500 and 3,000 m below the ocean floor—and must be evaluated using sophisticated geological studies and tapped by means of costly drilling operations. The costs of extraction are particularly high when the oil is offshore. A drilling ship costs $300,000 to $500,000 a day, and taking into account all the costs for personnel and other equipment, expenditures for the search for oil can easily reach several million dollars every day.

The hunt for petroleum requires the combined skills of scientists from very different disciplines, including geologists, geophysicists, and geochemists—all of them on the lookout for very specific geological structures. Oil deposits are often under high pressure, and contain salt water and natural gas. They are usually confined by a rock stratum that must be both permeable and capable of storing the liquids. Oil is created in a layer that lies even deeper, called the source bed, from which hydrocarbons typically migrate in the form of small drops into a reservoir. That migration stops beneath an impermeable layer of clay or rock salt, for example.

It is exactly "traps" like these that the oil companies search for—a job that involves screening layers of rock. This process begins by dispatching ships equipped with special microphones called geophones to a location where it is believed oil can be found. Air guns are used to create sound waves that penetrate the sea floor, where they are reflected at the boundaries of different rock strata. By means of these reflected waves, scientists can define the stratification beneath the sea bed and determine whether there are layers that can serve as reservoirs for oil or gas. If the results are promising, the first test bores follow. This stage of drilling tells geologists whether there is any gas or oil present, and provides an indication of the size of any reservoir that may be found.

If these results are positive, production can begin. In shallow waters oil companies use drilling platforms. "Jack-up platforms," for example, have legs that are lowered to the sea floor and are suitable for depths of up to about 100 m. "A semi-submersible," on the other hand, is a floating platform that either is anchored to the sea bed or relies on auxiliary motors to stabilize itself. One thousand meters is the maximum depth for this type of platform. If an oil deposit is even deeper beneath the sea, drilling ships are used, which also use auxiliary motors to maintain their position. Called "thrusters," these motors also have to work against the torque of the drill to keep the ship from revolving on its axis.

All of this amounts to a formidable challenge. "Oil production vessels and drilling platforms must precisely hold their positions even in stormy seas—otherwise drill pipes can break, which can cause damage costing tens of millions of dollars," says Jürgen Moser, Senior Expert at the Siemens Energy Sector in Erlangen, Germany. And that’s exactly what thrusters are designed to prevent. For these powerful drive units, dependability is not an option. They simply must never break down. "In addition to having a very secure power supply, these units must be ready for service even if an electrical subnetwork on board the ship fails," says Moser.

Reliable Propulsion. Considering the challenges of deep ocean drilling, it is easy to see why conventional on-board power supply systems on drilling ships feature redundant designs—two separate on-board networks, each with its own diesel generators. However, such generators usually run inefficiently under low partial loads. So if one network fails, half of the thrusters also stop running.

"That’s an especially big problem if it occurs just when some of the thrusters in the remaining subnetwork are down, for example when they’re being serviced," Moser explains. "You can’t simply feed power from the subnetwork that’s still operating to the one that’s stopped running, because this would cause a very high current to flow in the transformers." With this in mind, Siemens and U.S.-based Transocean, have developed a system based on SIPLINK (Siemens Multifunctional Power Link) technology that makes the on-board power supply more reliable. On ships equipped with SIPLINK, each thruster is supplied by both networks, which are connected by a Y-shaped switch consisting of high-performance transistors. "If one of the networks stops operating, it’s not necessary to switch over to the other one, and current spikes don’t occur in the transformer," says Moser, "What’s more, it’s no problem to feed electricity from one subnetwork into the other, for example for powering the drills, mud pumps, or lighting, some of which are connected to only one network." Finally, the system makes it possible to achieve energy savings of up to 30 %, because the diesel generators in both subnetworks can be optimally operated for each specific need.

The first drilling platform to use the SIPLINK system has been operating since May 2008 in waters off the coast of Nigeria, and a second platform is being converted for the system this year in Singapore. Transocean is also having new drilling ships built in South Korea. The vessels will be equipped with the SIPLINK system, with the first of these expected to enter service before the end of 2008.

"SIPLINK can be installed in any ship or on any drilling platform whenever a major overhaul is planned," says Moser. "And the costs of the system are no higher than those of a conventional solution."

Yet another major challenge in offshore oil production is getting the oil to shore, a job that’s usually taken care of by pipelines or tankers. To ensure that tankers don’t have to wait long, the oil is often pre-processed and temporarily stored in Floating Production Storage and Offloading (FPSO) vessels. An FPSO vessel stays in waters either very close to the drilling platform or to the drill holes on the sea floor.

Among other things, Siemens supplies measuring technology, telecommunications systems, and electrical networks for such ships. A ship’s entire electrical system is contained in an "E-House"—a gigantic, specially designed container that can be custom-tailored to the needs of any customer and manufactured in advance at inland locations. "The E-House is installed on deck rather than below decks," explains Knut Arne Thanem, Senior Project Manager at Siemens Oil & Gas Offshore AS in Oslo, Norway. "That saves space for petroleum."

Siemens experts have already designed a two-story E-House with a surface area of 15 by 30 m for a Norwegian customer. It was built at an on-shore facility in Dubai in 2007 and 2008 and installed on board its ship at a coastal dry dock there in August 2008. "We delivered the E-House complete with all the electrical components—it only had to be lifted with a crane onto its prepared base," Thanem says. "That saves a lot of time and money." Siemens has already designed another E-House for a sister vessel.

Offshore Future. Even with all of Siemens’ advanced technologies, however, oil production on the high seas is still a job that requires tremendous investments of labor and capital. But the investment is worth the effort. About one third of all petroleum produced worldwide today comes from offshore deposits, and experts estimate that roughly 25 % of all reserves are beneath the seas. Well-known examples include the oil fields in the North Sea, in the Gulf of Mexico, in Azerbaijan, and off the coast of West Africa.

And more offshore deposits have been making headlines of late. Brazilian oil company Petrobras, for instance, recently discovered two large reservoirs: the "Tupi" field, found in November 2007, 250 km off the coast of the State of São Paulo, is believed to hold deposits of between five and eight billion barrels, or about 1,000 bill. l; and the "Carioca" field, which made headlines worldwide in April 2008. The field is 270 km south of Rio de Janeiro and reported to be about as large as Tupi. More exact numbers regarding its size will not be available until 2009, however.

"The most promising oil fields of the future are at sea—off the coasts of Brazil, Angola, and Nigeria, as well as several patches in the Gulf of Mexico. Saudi Arabia also has offshore oil reserves," says Dr. Werner Zittel of Ludwig-Bölkow-Systemtechnik GmbH in Ottobrunn, Germany. Zittel is among the experts active in the Energy Watch Group (EWG) organization. "All of these oil fields are very difficult and expensive to open up, however." Brazil’s Tupi field is a good example. The oil there is at a depth of 7,000 m and covered by a layer of salt 2,000 m thick. So it will take several years before the Tupi oil finds its way onto the world market.

Down to the Last Drop. But while the world waits for Brazil’s offshore oil, other fields are drying up. The output of the North Sea reservoirs peaked in 2001, for instance, and several fields in the Caspian Sea are fast approaching their peaks. The amounts being extracted from other deposits, on the other hand—for example in the Gulf of Mexico and off the coast of Africa—are still rising modestly.

And The average lifes span for a reservoir is ten to 20 years, and some fields are even active for 30 years. "Offshore fields are being exploited faster in order to recover the high costs of drilling in less time," says Hilmar Rempel of Germany’s Federal Institute for Geosciences and Natural Materials (BGR) in Hannover. "Due to intensive extraction, these fields are being exhausted more quickly than oil fields on land."

To obtain maximum yield from offshore reservoirs, oil companies are applying increasingly sophisticated technologies. In fact, if all they relied on was natural pressure, only between ten and 30 % of the oil could be extracted. "Secondary processes" involve forcing water or other substances into the reservoirs to maintain internal pressure. This boosts the level of oil extraction to as high as 60 %. Yield can also be increased by means of a technique called "steam flooding," which calls for injecting superheated steam with a temperature of 340 °C into the deposit under high pressure.

And extraction equipment on the sea floor, installed and maintained by robots, is becoming increasingly important. (see Pictures of the Future, Spring 2004, Going for the Gas) Located directly at the source, robotic systems can separate undesirable substances such as water and sand from crude oil, for example, making extraction more efficient.
                                                                                                               Christian Buck