It is interesting to know that more than 56.6 million barrels of oil are produced daily by the top 10 oil and gas companies. The United States alone consumed a total of 6.87 billion barrels in 2011 based on figures by the US Energy Information Association, according to the "Oil & Gas IQ Countdown 2014" penned by Sumit Dutta.  The number represents 22% of total world petroleum consumption.

Over the years, the traditional major players have seen tougher competition from the growing number of national oil companies for the sole rights to major oil reserves. At the moment, global oil reserves are at 1.38 trillion barrels which is expected to last for 46.2 years.

In this list, we will identify the top 5 biggest oil and gas companies in the world according to the volume of oil and gas they produce every day. published by Energy Digital magazine.

1. Saudi Aramco

Barrels Produced Per Day (As of 2012): 12.5 million

Headquarters: Dharan, Saudi Arabia

Revenue: US$356 billion

With an equity of 2.4 million barrels per day, Saudi Aramco is the sixth largest refiner of oil. For 80 years, the state-owned oil company have grown to become a world leader in hydrocarbon exploration, refining, distribution, shipping, and marketing. It has also emerged as the top exporter of crude oil and natural gas liquids.

2. Gazprom

Barrels Produced Per Day: 9.7 million

Headquarters: Moscow, Russia

Revenue: US$158 billion

Despite being a private company, majority of Gazprom is state-owned. The company holds the world's largest natural gas reserves accounting for 14 percent of global and 74 percent of Russian gas output. Its major focus is on geological exploration, production, transportation, storage, processing and sales of gas, gas condensate and oil, sale of gas as vehicle fuel and generation and marketing of heat and electric power.

3. National Iranian Oil Company

Barrels Produced Per Day: 6.4 million

Headquarters: Tehran, Iran

Revenue: US$ 85 billion

The National Iranian Oil Company focuses its operations in exploration, drilling, production, research and development, refining, distribution and export of oil, gas, and petroleum products. It was slated to become BP-AICO (Anglo Iranian Oil Company), which owned the rights to all Persian oil resources but it became a state owned company in 1951. Currently, it holds 156.53 billion barrels of liquid hydrocarbon and 33.79 trillion cubic meters of natural gas.

4. Exxon Mobil

Barrels Produced Per Day: 5.3 million

Headquarters: Texas, USA

Revenue: US$ 453.12 billion

Exxon Mobil is the world's largest publicly traded international oil and gas firm. It is also the top refiner and marketer of petroleum products and its chemical company is also included among the world's largest. The American oil company operates in many countries and is known by the brand name Exxon, Esso, and Mobil.

5. Petro China

Barrels Produced Per Day: 4.4 million

Headquarters: Beijing, China

Revenue: 2 Trillion Chinese Yuan / US$330.08 billion

Petro China is the largest oil and gas producer and distributor in China. It is the second largest company in the world in terms of market capitalization. It has over half a million employees, which makes it the biggest employer in the top five.