From Longman Business Dictionary
OPECOPEC /ˈəʊpekˈoʊ-/ nounCOMMERCEORGANIZATIONS Organization of Petroleum Exporting Countries; an organization of nations that produce and sell oil and which tries to keep the price of oil at a suitable levelPractically all payments to OPEC countries are made in dollars.
the reduction in demand for OPEC oil