Reaching an agreement on extending the Opec+ production cuts was a simple affair this week in Vienna. Matters were effectively finalized during the previous week’s G20 meetings in Osaka before any participants even arrived in Vienna. Saudi Crown Prince Muhammad bin Salman and Russia’s President Vladimir Putin endorsed an extension during bilateral talks in Osaka.

If there had been any doubts over the likelihood of a deal, these were swiftly dispelled by Iranian Oil Minister...