OPEC’s decision this month to roll over its oil output cuts displayed a rare sense of cohesion from the cartel, but there are signs that de-facto leader Saudi Arabia is seeking an eventual end to intervention. The extension of the cuts to the end of March next year (on the same terms as those agreed in November) should be enough to bring crude stocks back to their five-year average, a target regularly cited by OPEC. Nonetheless, oil prices have fallen by 5% over the past few days as investors tha…