Upcoming sanctions on Russian oil are set to be “really disruptive” for energy markets if European nations fail to set a cap on prices, analysts warned.The 27 countries of the European Union agreed in June to ban the purchase of Russian crude oil from Dec. 5. In practical terms, the EU — together with the United States, Japan, Canada and the U.K. — want to drastically cut Russia’s oil revenues in a bid to drain the Kremlin’s war chest following its invasion of Ukraine.However, concerns that a complete ban would send crude prices soaring led the G-7 to consider setting...