Scottish First Minister Alex Salmond announced plans for a referendum on independence in 2014. His government maintains it could support itself financially in large part though oil and natural gas developments in the North Sea.
Abdalla el-Badri, secretary-general of the Organization of Petroleum Exporting Countries, said in an interview published Monday by The Daily Telegraph most of the reserves in the North Sea are depleted.
The Scottish government, however, estimates there are more than 20 billion barrels of recoverable reserves left in the North Sea. Salmond released a paper in May saying the Scottish energy industry contributed about $39.5 billion to the gross domestic product in 2011.
The British government challenges the claims. An audit last year by the Institute of Fiscal Studies in London said "an independent Scotland would face a bigger fiscal adjustment than the rest of the U.K."
Badri said both governments benefit from unity, adding the referendum has little to do with OPEC itself.
"Myself, I don't see how England will stay without Scotland and Scotland stay without England," he said. "This is how we all grew up, with the U.K., not with Scotland and England."