Natural Resources - Reserves

As demand for oil increases, attention is shifting to deposits that were previously too expensive to exploit, such as deep-sea reserves and oil sands. Another exciting technology is natural gas liquefaction.

Crude oil and natural gas meet more than half of the world’s energy needs. "But due to economic and demographic developments, in the next 50 years we’ll have to produce around one-third more crude oil and about three times more natural gas than we do now," forecasts Wolfgang Stahl from Germany’s Federal Institute for Geosciences and Natural Materials. The problem is that the age of cheap oil is coming to an end; according to the International Energy Agency (IEA), exploitation of conventional sources will peak within the next decade.

Predicted extra demand could be met by resources that were previously too expensive to tap. At today’s oil price of 20 to 30 dollars a barrel, it would be economically viable to exploit sources such as oil sands (see box) and remote gas reservoirs. Experts believe that there are large oil and gas deposits below the ocean floor at water depths of between 500 and 2,000 m, which makes drilling extremely difficult. "Fixed oil rigs are not up to this task," explains Fritz Kleiner of Siemens Power Generation (PG) in Erlangen. Floating rigs may provide an answer, but must expend significant amounts of energy since natural pressure is often too low to bring the oil the long distance to the surface. As a result, some of the production systems will have to be set up on the ocean floor itself. A whole army of robots will be needed to build and maintain such underwater platforms. Some will be remote-controlled from on board a ship, while others will work completely independently. The materials used in such facilities will be subjected to enormous pressure and corrosive seawater. "Their electronic components will have to be as reliable as possible, because every repair will be extremely expensive," says Kleiner.

With a view to ensuring the survival of such facilities, a team headed by Joost Wijnant at Siemens PG in Hengelo, Netherlands, has developed non-sealed compressors with magnetic bearings. These do not require any lubricating oil and remain maintenance-free for many years. "We’ve fitted 15 machines on land with the compressors," says Wijnant. "Later they’ll work offshore, and then we’ll be able to reach the ocean bed." The first completely autonomous underwater pumping station is due to be opened at the Ormen Lange gas field in 2007. The field is operated by several oil companies as well as Norway’s state-run Petoro. The station will be 120 km off the Norwegian coast at a depth of 800 to 1,100 m. Due to harsh weather, the area is only accessible five months a year.

Liquid Natural Gas. While crude oil is becoming increasingly difficult to obtain, plenty of natural gas is still available. With increasing gas prices, it now makes economic sense to utilize this former byproduct of oil extraction even at remote deposits. Liquefied natural gas (LNG) has been shipped in tankers since the late 1960s, but oil companies have recently started chemically converting gas to a synthetic crude oil directly at source. In this gas-to-liquid (GTL) process, the carbon atoms in the natural gas (mainly CH₄) are formed into chains containing up to 20 links. Industrial companies can then use the liquid hydrocarbon mixture to produce various fuels, particularly diesel.

Today, the process is so efficient that the cost of sulfur-free GTL diesel is comparable to that of purified fuels produced with crude oil. "Lots of new gas refineries will be built in the coming years," predicts Mirko Wutkewicz of Siemens Corporate Technology in Erlangen. Shell and South Africa’s Saso, for example, are investing $5 billion in two GTL plants in Qatar. Plans call for these plants to produce 177,000 barrels of diesel, kerosene, lubricating oils, naphtha and paraffins per day by 2011. In the GTL process, which was developed by German researchers Franz Fischer and Hans Tropsch in 1925, methane is converted with oxygen at high temperatures into synthesis gas, which is a mixture of hydrogen and carbon monoxide. This accounts for up to 60 % of overall production costs. Particularly expensive is the oxygen, which is obtained by means of energy-intensive air liquefaction. "But in ten to 15 years, it may be possible to cheaply extract oxygen from air with ceramic membranes similar to the ones in oxide ceramic fuel cells," states Wutkewicz. Synthesis gas is also produced in new coal-fired power plants known as IGCC plants (see Clean Future).

In stage two of the Fischer-Tropsch process, synthesis gas reacts to form waxy paraffins. These long-chain hydrocarbons are then cracked. Depending on the catalyst selected, the proportion of the various hydrocarbons in the crude oil can be varied at will. The industrial sector prefers intermediate fractions, which are used to produce diesel and kerosene. But because this production method is energy-intensive, GTL diesel creates around the same amount of carbon dioxide as conventional fuels.

Designer Fuels. The key advantages of GTL diesel are that it’s especially clean and contains almost no sulfur or aromatic hydrocarbons, such as benzene, which is carcinogenic. With the help of additives that replace sulfur and have a similar lubricating effect, GTL diesel can be used in any diesel engine—and with fewer emissions of harmful gases, as was recently confirmed by a test conducted by VW and Shell. Engine developers are enthusiastic about GTL diesel.

That’s because it paves the way for the creation of designer fuels that are modified specifically for certain engine types. "New emission limits can be adhered to only if fuel composition is precisely defined," says Dr. Herbert Stocker, who is responsible for coordinating advanced development at Siemens VDO Automotive Powertrain in Regensburg. With this in mind, the EU has already established that by 2005 diesel may contain no more than 0.005 % sulfur. And that’s set to drop to 0.001 % by 2011.

Ute Kehse