PetroChina, Royal Dutch Shell, ExxonMobil, Saudi Aramco and British Petroleum are some of the top petroleum companies in the world when measured by revenue in U.S. dollars, as of 2014. However, when measured in terms of oil produced per day, Russia's state-owned Gazprom and the National Iranian Oil Company are the second and third largest oil companies in the world respectively. Many of the companies with the highest revenue earn much of it through refining consumer products.
Founded in 1999, PetroChina has grown quickly to become the largest of China's three giant state-owned oil companies. The company produces 4.4 million barrels of oil per day and has invested heavily in African oil fields.
Created in 1907, Royal Dutch Shell produces 3.9 million barrels per day but generates much of its revenue through gas stations and automotive motor oils. ExxonMobil and British Petroleum produce 5.3 million and 4.1 million barrels per day respectively and have similar business models to Royal Dutch Shell. The companies have been in business a long time, have oil and gas fields worldwide and produce billions of dollars in consumer products.
Saudi Arabia's Aramco is one of the biggest however it is measured. Aramco produces over 12 million barrels oil per day which generates $1 billion per day in revenue. Only Aramco pumps more oil than Gazprom's 9.7 million barrels per day. However, Gazprom does not report its revenues, a significant portion of which are not transacted in U.S. dollars or open markets.
The National Iranian Oil Company is the third largest oil producer in the world, but due to international sanctions because of the country's nuclear program it has had a hard time selling it.