New Delhi, June 29 -- Oil majors have two ways to make big money during an energy shock. One is to sell the hydrocarbons they pump and refine themselves. The other is to buy barrels that others produce and flog them to whoever wants them most. The third Gulf war has demonstrated just how important the latter has become as a source of profit for the industry-particularly in Europe.

Trading used to be the majors' dirty little secret for topping up returns. It is not little anymore. The volume of hydrocarbons traded by BP, Shell and TotalEnergies-equivalent to 40-50m barrels of oil per day-is five to ten times what they produce. Nor is the contribution to their profitability a rounding error. Our calculations suggest the trio's trading arms...