What is the oil price? For years, the answer has been provided by one of the two leading global benchmarks – Europe’s Brent and US-based West Texas Intermediate. As much as three quarters of the world’s physical oil is priced each day using them as yardsticks.

In fact they represent only a fraction of the hundreds of different crudes traded globally. Petroleum Intelligence Weekly’s International Crude Oil Market Handbook, a traders’ bible, lists almost 200 different crudes, from Kutubu of Papua New Guinea to Caño Limón of Colombia.