Analysts said the scale of the spike was largely down to short-term speculators who had sold oil they did not hold, believing prices would fall further, and then having to buy it back on the last day of the Nymex October West Texas Intermediate contract. Otherwise they would actually have had physically to deliver the oil to their counterparties.
Meanwhile Nymex November prices rose to more than $106, up from a low point last week of $90, partly due to concerns about tightening supply in the wake of hurricane-related disruption, concern over Nigerian output and continued heavy oil demand from China. OPEC output, meanwhile, is believed to be at a record level of 32.5m barrels a day.