Under the sea

Underwater cables and pipelines have been used for almost two centuries to carry power, raw materials and to enhance communications, as E&T explains.

At the western edge of Alexandria's famous 'corniche', few of the guests sipping a lazy pre-lunch drink on the terraces of the Greek Club would have any notion of what lies under the shimmering sea spreading out before them. Imagine their surprise, therefore, when on a sunny winter's day in January 2008, a ship's anchor sliced through a couple of underwater cables near the ancient port, severing electronic communications between Europe and Asia. Around 85 million users from Egypt to India were cut off for days.

Underwater cables have been with us for quite some time. In 1811, a power-cable was laid across the Isar River in Bavaria. In those early days, cables consisted of copper conductors insulated with paper and sheathed in lead. Cumbersome perhaps, but soon everybody wanted them to hook in to ever widening network of telegraph communications. Technology, however, rarely moves in a straight line.

In 1850, the telegraph cable laid between Dover and Calais went dead. It consisted of a copper core insulated with gutta-percha, a brownish leathery material derived from the latex of rubber trees. Naturally, the finger pointed to the malice of French fishermen. The new line laid in 1851 was armoured and no fishermen interfered this time.

Soon afterwards, another cable was laid between Dover and Ostend. Sweden and Denmark were connected in 1854. A telegraph line was even laid under the Black Sea in 1855, connecting Constantinople with Varna and the Crimea, to help with wartime communications. The real challenge was laying a cable across the Atlantic.

The years between 1857 and 1866 witnessed huge efforts to connect the two continents. The first cable was lost to sea. The second cable, in 1858, lasted but a month. However, aspirations to follow London share prices in New York and American cotton prices in London would not be denied. Steel-wire was adopted for armouring the line from Ireland to Newfoundland. The spread of the telegraph soon became unstoppable. By 1870, the government of British India could communicate directly with London.

Submarine power transmission

Overland power distribution is usually based on three-phase AC and overhead cables need no insulation. In submarine power transmission, as with underwater cables, the lines must be sheathed for mechanical protection and insulated against water and corrosion. Cables passing through areas of heavy surf are frequently protected by burial in trenches. The water can help keep cables cool and reduce resistivity, but there are other niggles that must be overcome.

In underwater AC power transmission, the capacitance between active conductors and surrounding metallic shields lead to transmission losses. The use of high voltage direct current (HVDC) eliminates both dielectric and sheath losses. For a given line voltage, thinner insulation needed for DC transmission makes cables both lighter and cheaper.

HVDC systems are potentially useful in bringing ashore power from ocean-based wind farms. The down side is the cost of conversion equipment needed at both ends, particularly expensive for shorter spans. Such DC links can also be used to isolate, say, two AC systems that may be operating at slightly different frequencies or with phases out of synch. Some long-range overland transmission systems, like the 'Pacific DC Intertie' in the US, are also based on HVDC.

In the UK, the HVDC link across the English Channel dates back to 1961. The original transmission power of the interconnector was 160MW. In 1986, a new 73km-long 2,000MW HVDC line was installed. Since 2005, about 5 per cent of power available in the UK is imported from France, quietly telling us the UK already has a power deficit.

Submarine oil and gas transmission

In the early 1970s, Italy considered importing gas from Algeria at a time when experience in submarine pipelines was confined to depths of less than 150m. A pipeline from Tunisia would have to cross the 610m-deep Channel of Sicily. From Sicily, the line would next need to cross the 270m-deep Straits of Messina, to the Italian mainland. New technologies were needed.

The impetus led ENI and its offshoot Saipem to develop some innovative technologies. Italy has since led the world in deep-sea pipe-laying operations. The first phase of the TransMed pipeline was constructed in 1978-1983 and the second in 1991-1994. The overland segments are single 48in lines, but the submarine sections across the Channel of Sicily and the Straits of Messina consist of three parallel 20in lines, with a capacity of 24 billion cubic meters (bcm) per annum.

Saipem's deep-sea pipe-layers were again called into action when the submarine sections of the Maghreb-Europe Gas (MEG) pipeline were laid across the Straits of Gibraltar. The 48in overland gas pipeline crosses from Algeria into Morocco and splits at Gibraltar into two 22in lines, laid across the 28 miles of the straits at a depth of nearly 400m. With a capacity of 8.6bcm, the supply to Spain was commissioned in November 1996 and the section to Portugal in March 1997 at a cost of $2.3bn.

When an oil or gas pipeline crosses into another country, transit fees need to be negotiated. Often, the host country expects to 'lift' some of the transmitted fuel, usually at a preferential rate. The two lines from Algeria were no exception. Unusually, the North African pipelines have successfully steered clear of the usual inert-state conflicts and transactions have remained firmly in the commercial sphere.

The construction of the Blue Stream gas pipeline across the Black Sea, between Russia and Turkey, was perhaps a little more contentious. It gave rise to much diplomatic chatter and media speculation, alongside important advances in the science and engineering of submarine gas transmission.

From the start, in 2001, Blue-Stream was greeted with scepticism as a technically difficult project. Running underwater for 236 miles, the twin 24in lines descended to the previously untried depths of 2,150m, the world's deepest underwater pipeline to date. As well as salinity and high hydrostatic pressures, Blue Stream is also exposed to the peculiar geochemistry of the Black Sea, with high concentrations of dissolved hydrogen sulphide below 200m, making for a very corrosive environment. Research was required before deciding to use pipes made of API X65 high-tensile strength low-alloy steel, protected against corrosion with three layers of polypropylene coating. The project cost $3.5bn.

From the outset, Russia's Gazprom co-opted Saipem-ENI as equal partners. ENI's technical know-how in deep-sea pipe-laying was crucial to technical success. The Italians guaranteed trouble-free operation for 36 years. The underwater gas pipeline section is checked twice a year using a submersible vehicle and by pushing special flaw detector plungers through the pipeline. On the Russian side, the pipeline route is crossed by multiple canyons forcing numerous detours. With precise installation of the pipeline more necessary than ever, the giant floating platform Saipem 7000's dynamic positioning system was used for work in up to Force 6 seas.

With Washington issuing dire warnings against increased dependence on Russian natural gas, the opposition faced by the Turks from their principal ally was nearly as corrosive as the lower depths of the Black Sea. A good decade after the end of the Cold War, it all seemed a little peculiar. It now seems NATO and the EU were determined to push the Russians as hard as they could. Yeltsin's political demise and the advent of Vladimir Putin was perhaps more significant than most people realised at the time. Meanwhile, Blue-Stream moved forward and turned out an engineering marvel. The first gas was pumped in February 2003; the full annual capacity of 16bcm will be reached in 2010.

European energy imports

In 2007, Europe imported nearly 500 million tonnes of crude oil and 250bcm of natural gas, of which 150bcm came from Russia, about a quarter of Europe's total natural gas consumption.

Despite Brussels' frequent pronouncements on renewable energy, fossil fuel imports are expected to grow. The question for Europe is where to go for safe and secure supplies. For crude oil, there is no immediate problem as the EU has numerous maritime supply options. Gas transmission, however, is a different matter.

In Brussels, there is concern that political strings could be attached to future gas supplies. The likelihood, however, is that Russia would sooner raise the price of gas than shut off the taps. Before the recession, the EU in 2008 was already buying Russian and other gas at inflated prices, around $370 per 1,000 cubic metres, compared to the $130 they had been paying in 2001-2. Moscow has been lobbying major exporters of natural gas, including Iran and Qatar, to form a natural gas cartel - a 'gas Opec'. For Europe, this can only mean yet higher prices. Russia is vying for influence with Europe's other gas providers. That alone may lead to a convergence of prices at relatively high levels in the medium term.

Meanwhile, Russia's troubles over gas transmission through Ukraine continue. The present contract with Ukraine requires settling debts in the first week of every month, a near certain formula for conflict. Russia's concerns are, therefore, very much alive. With Blue Stream an impressive technical success, Moscow is increasingly interested in the use of submarine pipelines to avoid crossing the territory of troublesome neighbours.

The first of two such pipelines is South Stream. Pointedly and rather expensively bypassing Ukraine and Romania, it would run from Zhubga (where Blue Stream leaves Russian shores) to Bulgaria, across the Black Sea. Its projected capacity has recently been nearly doubled to a somewhat improbable 63bcm. Whether Gazprom has the gas to fill this line, or indeed Russia the capital resources to begin construction is part of a rapidly changing reality, reflecting oil price fluctuations. Moscow is openly promoting this project as a rival to the Nabucco pipeline, which aims to convey to Europe that elusive prize, natural gas free of Russian influence.

The second submarine option is a pipeline across the Baltic Sea directly to Germany. Initially, Nord Stream would have been supplied from the Stockman gas field in the Barents Sea. The first phase is projected to pump 28bcm, with the total load eventually rising to some 55bcm. However, the Russians are known not to have the engineering know-how to drill at much deeper than several hundred metres of water and the Stockman field presents both greater depths and a severe operating environment.

Meanwhile, Moscow has cancelled its contracts with the international oil companies over Stockman. In the absence of this source, observers have been wondering whether Gazprom would simply reduce Western Siberian supplies through the Ukrainian system and short circuit the gas directly to Germany. When it comes to energy supplies, Europeans too are not incapable of seeking advantage at the expense of their allies.

Russia's Baltic neighbours have been objecting vigorously to Nord Stream's chosen route on environmental grounds and complaining about the loss of transit revenues. The project nevertheless appears to be on track, with German financial backing looking to see the project through to completion.

Talking about contentious pipeline projects, nothing holds a candle to a future trans-Caspian gas pipeline that would run from Turkmenistan's natural gas fields to Baku, then cross Georgia and Turkey to South Eastern Europe.

If ever considered seriously, this line would change many assumptions governing the geopolitics of Eurasian energy transmission. Buying natural gas in Russia's 'back-yard' would have incendiary consequences for Russo-Turkmen ties, with repercussions possible all across the spectrum of what we used to call 'East-West' relations.

But not to worry! It is not likely to happen soon. Even so, nothing will be quite the same again on the terraces of the Greek Club in Alexandria.

Recent articles

Info Message

Our sites use cookies to support some functionality, and to collect anonymous user data.

Learn more about IET cookies and how to control them

Close