Buried in the small print of an obscure trade agreement between Europe and South Korea is a clause which is costing oil consumers around the world money.
The agreement removed South Korea's tariffs on imports of crude from Europe, making it economic to ship large volumes of global benchmark North Sea oil to the Asian country and boosting its price - in turn making oil more costly for importers around the world.
North Sea crude is vital for global oil markets because more than half of the world's international oil trade is priced against the dated Brent benchmark, consisting of four UK and Norwegian North Sea crudes with Britain's Forties the most important.
Dated Brent is also used to settle Brent crude futures.
"Brent is a global pricing benchmark and it should reflect supply and demand, not a flow of a certain type of crude to a certain country," said Olivier Jakob at energy consultancy Petromatrix. "The artificial economics of the flows to South Korea starts to have too significant of an impact on the price-discovery value of the Brent contract."
Before a July 2011 free trade agreement between the EU and South Korea, only occasionally would the economics work to ship a cargo of Forties crude to Asia. But the agreement removed import tariffs on oil from the EU and Norway, making imports 3 percent cheaper than non-European grades.
At current prices above $100 a barrel this implies a discount of over $3 per barrel, enough to cover most of the freight costs for a very large crude carrier (VLCC) from the North Sea to the Asian country half a world away.
As a result, inter-continental shipments have soared despite the fact that the arbitrage - the price difference between the two locations including shipping costs - is very often unprofitable.
"Arbitrage is of course a necessary precondition for a functioning global benchmark as it is the core mechanism that ensures one region does not get out of synch with another," said David Wech at consultancy JBC.
"This argument works for all grades, except the price setter of dated Brent - Forties. Indeed the arbitrage of even one VLCC of Forties will have a disproportionately strong impact on the Brent complex," he added.
WHO PAYS MORE?
Ship tracking data for December to the end of May shows oil majors such as BP, Royal Dutch Shell and trading house Vitol shipped 11 VLCCs of North Sea crude, mostly Forties, to South Korea, with flows averaging 120,000 barrels per day (bpd).
Although the volume accounts for only 0.1 percent of global annual consumption, its significance for the oil markers is huge as the flows account for a third of total output of Forties.