The biggest oil companies that control and manipulate the price of Oil through the stock market, are BP, Total, Exxon, Shell..etc...all of them are producers and refiners... and control more oil out put than Opec combined. Opec may have played a political force during the cold war, but now it is an irrelevent organisation and effect on the oil price is minimum...None of the members respects their respective quota, they always produce above what was discussed, yet the prices keep climbing. Prices are more or less affected to a small degree by political unrests, and the rest by Wall Street.