Comparing the market value of petroleum companies, ExxonMobil, Chevron and PetroChina are the three world's largest oil companies as of 2015. Based on 2014 revenues, the biggest petroleum companies are Sinopec, PetroChina and Royal Dutch Shell.
Other companies among the top 10 oil companies based on market value as of 2015 include Total, BP and ConocoPhillips. Yearly revenue comparison shows slightly different companies in the top 10, including Kuwait Petroleum Corporation or Lukoil.
According to daily oil production, the three world's biggest oil companies are Saudi Aramco, Gazprom and National Iranian Oil. Saudi Aramco produces 12 millions of oil barrels per day, while Gazprom makes 8.3 millions of barrels per day.