* Shell taking up to 4 supertankers of January Forties toAsia
* Forties differentials surged to 23-month high in December
* Brent spread rallies even as outright price slumps
By Alex Lawler
LONDON, Jan 13 (Reuters) - As oil prices fall to newmulti-year lows on a global glut, the structure of the niche butcrucial benchmark Brent market has shown counter-intuitive signsof tighter supplies and strengthening.
The reason, according to some in the market, was an unusualaccumulation of British Forties crude oil cargoes by Royal DutchShell, and the expected shipment of many of these outof Europe to South Korea and China.
Shell may have bought more than half of the Forties cargoesloading in January, according to estimates from North Sea crudetraders. Price differentials for Forties, which is the largestof the four North Sea crudes that underpins the dated Brentphysical benchmark, rose.
"I think it has to do with Shell's position," said a NorthSea trader with another company, referring to the strengtheningin Forties differentials seen during late December. "Lack ofForties availability."
A spokesman for Shell, which usually does not comment ontrading, declined to comment on Wednesday.
In January, Shell is shipping three or four Very Large CrudeCarriers of Forties to Asia, according to Reuters shipping dataand trade sources. If all sail, that would be about 8 millionbarrels, more than half of the month's Forties production.
South Korea is a regular buyer of Forties as its crudeimports from the European Union are tax-free under a free tradeagreement. Still, four supertankers of Forties heading eastwould be an unusually large volume - the most that one tradercould recall seeing in a single month.
While the outright price of Brent crude - which traded at$30.34 a barrel on Tuesday, near a 12-year low - was falling,Forties and the wider Brent market were getting stronger.
Forties price differentials
Short-term swaps called contracts for difference(CFDs) usedby traders to hedge price risk briefly shifted to a premium forsupplies for prompt delivery - a structure known asbackwardation and unusual when supply is generally ample.
In a further sign of unusual strength, the spread betweenthe prompt and second-month Brent futures prices rose sharplyeven as the outright price of Brent tumbled.
The spread moved into backwardation on Wednesday, a daybefore the February Brent contract expires, while the rest ofthe Brent market remains in the opposite structure, contango,until 2017.
Another reason for the strength in differentials was biddingby oil refiner Petroineos for Forties cargoes, which in the viewof other market sources were unlikely to be sold as they wereheading for Asia.
"You could say Petroineos was bidding into a vacuum as Shellwas unlikely to sell the cargoes," said an industry source whodeclined to be identified. Petroineos did not immediatelyrespond on Wednesday to a request for comment on why it wasbidding.
There are a small number of participants in the Fortiesmarket and it is not uncommon for them to accumulate largepositions and this does not contravene any regulations.
Shell itself took a similarly large Forties position fouryears ago, trade sources said at the time. (Additional reporting by Simon Falush; editing by WilliamHardy)
