The members of the Organization of the Petroleum Exporting Countries reached a preliminary agreement to limit the group's daily production to between 32.5 million to 33 million barrels a day at the end of September. Today the oil exporters meet in Vienna to define the levels of production for each country. OPEC encompasses 40% of the world's oil supply, so traders will be closely watching this meeting to find clues on which way oil prices will go. The meetings are usually closed to the press, but senior officials are open to the reporters and gladly answer questions throughout the day. A formal statement, the cartel's objectives and takeaways from the discussions are usually released after the meeting, but the volatility will be surely sensed during the whole day.