Saudi Arabia's Oil Minister Ali al-Naimi attends the opening of the Ministerial Conference of the Organisation of Arab Petroleum Exporting Countries (OAPEC) in Doha on December 21, 2013. Naimi said he was "optimistic" regarding the outlook for the world oil market in 2014, which he expects to remain stable.  AFP PHOTO / AL-WATAN DOHA / KARIM JAAFAR == QATAR OUT ==        (Photo credit should read KARIM JAAFAR/AFP via Getty Images)