ORMEN LANGE was a Viking ship, the biggest in its day and celebrated in Norse sagas. With its 60 oarsmen and terrifying dragon’s head at the bow (Ormen Lange means “long snake”), it was a fitting name for a giant gasfield that will supply a fifth of Britain’s gas needs for years to come.

But Norway’s rampant Viking raider is now to face questioning by men in dark suits in Washington. No one doubts that the gasfield — 40km long and eight wide — is huge. Why would a leading oil company invest in a 1,200km pipeline across the North Sea if Ormen Lange was a mere Viking legend?

Shell yesterday found a problem. Bitten badly by past mismanaged reporting, it is being scrupulous and its initial decision to book most of its entitlement to Ormen Lange gas is being reversed. The problem relates to the use of threedimensional seismic data to define the area of “proved reserves”. This is not permitted under SEC rules without corroborating evidence, and Shell has backtracked.

BP and Norsk Hydro disagree; they have booked most of their Ormen Lange gas. Norsk Hydro says the project is going ahead, the Government has blessed it and drilling contracts have been tendered. Who is right? Shell’s troubles have put the spotlight on a huge dilemma that other oil companies would love to sweep under the carpet. Their pleas will be ignored, not because of the SEC, but because it is the world, not just investors, that wishes to know whether or not the tank is really full.

Ormen Lange’s 400 billion cubic metres of gas is key to Norway’s ambition to capture a large share of the UK gas market as North Sea reserves dwindle, but the long snake has caused trouble since its discovery in 1997. The field will now become the focus of an inquiry by the SEC.

This is a gas development at the cutting edge of technology, requiring sub-sea wells in depths of more than one kilometre and pipelines that will climb a 300 metre sub-sea cliff. The project has also been plagued by a row between Britain and Norway about jurisdiction over the pipeline that will bring the gas to the UK.