Companies

• Anadarko Petroleum Corporation -- The Texas-based Anadarko is among the largest independent oil and natural gas exploration and production companies in the world, with 2.4 billion barrels of oil equivalent of proved reserves at year-end 2010. Anadarko's portfolio of assets encompasses premier positions in U.S. onshore resource plays in the Rocky Mountains region, the southern United States and the Appalachian Basin. The company also is a premier deepwater producer in the Gulf of Mexico, and has production in Alaska, Algeria, and Ghana with additional exploration opportunities in Brazil, China, Indonesia, New Zealand, and East and West Africa.   
• BP -- UK's BP is one of the world's largest energy companies. The BP group operates across six continents, and its products and services are available in more than 100 countries
• ENI -- Italy's Eni SpA, one of the world's top energy companies, engages in the exploration, production, transportation, transformation, and marketing of oil and natural gas, today with operations in 77 countries. The company also involves in the production and sale of electricity; refining and marketing of petroleum products; production and sale of petrochemical products and hydrocarbons, etc.
• Enterprise Products Partners L.P. (EPP) -- Houston-based EPP is the largest publicly traded partnership and a leading North American provider of midstream energy services to producers and consumers of natural gas, NGLs, crude oil, refined products and petrochemicals. EPD's assets include approximately: 50,200 miles of onshore and offshore pipelines; 192 million barrels of storage capacity for NGLs, refined products and crude oil; and 27 billion cubic feet of natural gas storage capacity. Services include: natural gas transportation, gathering, processing and storage; NGL fractionation, transportation, storage, and import and export terminaling; crude oil and refined products storage, transportation and terminaling; offshore production platform; petrochemical transportation and storage; and a marine transportation business that operates primarily on the United States inland and Intracoastal Waterway systems and in the Gulf of Mexico.  
• ExxonMobil -- Exxon Mobil is the world's largest publicly traded international oil and gas company.
• Halliburton -- The Houston-based Halliburton is the world's second largest oil services company.
• Hess Corporation -- The New York-based Hess Corporation (formerly Amerada Hess) is a global integrated independent energy company engaged in the exploration and production of crude oil and natural gas, as well as the refining and marketing of petroleum products, natural gas and electricity. Hovensa, a joint venture between subsidiaries of Hess Corporation and Petroleos de Venezuela, S.A. (PDVSA), operates a world-class refinery on the Caribbean island of St. Croix in the United States Virgin Islands. Built in 1966, Hovensa is in the top 15 largest refineries in the world (please see my post "World's Top 21 Largest Oil Refineries," here), with crude oil processing capacity of 500,000 barrels per day. Hess has exploration and production assets in the United States (Gulf of Mexico, North Dakota, Texas), Australia, Brazil, Equatorial Guinea, Ghana, Egypt, Libya, Indonesia, Malaysia, Thailand and the North Sea.  
• Korea Gas Corporation (KOGAS) -- KOGAS was incorporated by the Korean government in 1983. Since its founding, it has grown to become the world's largest LNG importer. As the nation's sole LNG provider, the Corporation is fully committed to providing clean, safe and convenient energy to the people of Korea. In keeping with this mission, KOGAS currently operates three LNG terminals and a nationwide pipeline network spanning over 2,739km in order to ensure stable supply for the nation. KOGAS has successfully expanded its scope of business from mere import and distribution of natural gas, to global projects including exploration and production, enabling it to secure a stable supply of energy and expand its business portfolios. 
• Marathon Oil Corp. -- Marathon Oil Corporation (NYSE: MRO) is an integrated international energy company engaged in exploration and production; oil sands mining; integrated gas; and refining, marketing and transportation. Marathon, which is based in Houston, Texas, has operations in the United States, Angola, Canada, Equatorial Guinea, Indonesia, IKR (Iraqi Kurdistan Region), Libya, Norway, Poland and the United Kingdom. Marathon is the fourth largest U.S.-based integrated oil company behind ExxonMobil, Chevron Corp., and ConocoPhillips, in the PIW's ranking for 2009. Also, it currently retains a Zacks #3 Rank. Marathon is the nation's fifth largest refiner for 2010 (please see here).
• Parker Drilling Co -- Houston-based Parker Drilling Company, through its subsidiaries, provides land and offshore contract drilling services and rental tools to oil and gas companies and integrated service providers worldwide. It also provides a range of services that are ancillary to its drilling services, including engineering and logistics, as well as project management services. Parker's international fleet includes 28 land rigs and two barge rigs in strategic markets, and its U.S. fleet includes barge rigs in the U.S. Gulf of Mexico. Parker's rental tools business supplies premium equipment to operators on land and offshore in the U.S. and select international markets. Parker's project management business includes multiple contracts for the design, construction or operation of customer-owned rigs, including operation of two extended-reach-drilling land rigs (also designed and built by Parker) and one offshore drilling platform. Founded in 1934, Parker has set numerous world records for deep and extended-reach drilling and is an industry leader in safety performance.
• Petrobras (Petróleo Brasileiro S.A.) -- Petróleo Brasileiro was founded in 1953 and is based in Rio de Janeiro, Brazil. It is a publicly traded corporation, the majority stockholder of which is the Government of Brazil. Petróleo Brasileiro S.A. engages in exploring, exploiting, and producing oil from reservoir wells, shale, and other rocks; refining, processing, transporting, and trading oil and oil products, natural gas, and other fluid hydrocarbons; and other energy related activities. It has a presence in 28 countries. Petrobras has been ranked fourth in the Platts Top 250 Global Energy Companies Rankings 2010, behind ExxonMobil, BP and Gazprom Oao---please see my post, here. Petrobras with a market capitalization of $229 billion, ranked at No. 3 in the PFC Energy 50 Ranking of World's Top Energy Companies, Jan 2011 reflecting 2010 Rank, after ExxonMobil and PetroChina---please see my post here. Also, Petrobras retained its spot as the No. 15, in the 2011 Petroleum Intelligence Weekly's/PIW's ranking for 2009. And Petrobras retained its spot as the No. 15 in PIW's Top 50 oil rankings announced in Dec 2011, for 2010. Petrobras Chief Executive José Sergio Gabrielli de Azevedo has been named by Energy Intelligence as its 2011 Petroleum Executive of the Year. Under Gabrielli’s leadership, Petrobras made discoveries expected to more than double its oil reserves and production in the years to come. The company has established itself as a leader in deepwater exploration and production technology with among the highest safety and efficiency standards in the business---please see my post "Brazil as a Role Model," here.                     
• PDVSA (Petróleos de Venezuela, S.A.) -- Petróleos de Venezuela S.A., the state-owned corporation of the Bolivarian Republic of Venezuela, is responsible for the exploration, production, refining, transport and commerce of hydrocarbons. The Venezuelan State is PDVSA’s sole stockholder under the provisions of the Constitution. PDVSA ranks fourth among the world's top oil companies, according to the 2011 PIW's ranking for 2009. Its exploration and production take place in Venezuela, but the company also has refining and marketing operations in the Caribbean, Europe, and the US. US-based subsidiary CITGO Petroleum supplies gasoline to some 6,500 US retail outlets. Outside Venezuela, PDVSA refines, markets, and transports petroleum products in Belgium, the Caribbean, Germany, Sweden, the UK, and the US.
• Rosneft -- Rosneft is the leader of Russia’s petroleum industry, and ranks among the world’s top publicly traded oil and gas companies. The Company is primarily engaged in exploration and production of hydrocarbons, production of petroleum products and petrochemicals, and marketing of outputs. Rosneft has been included in the Russian Government’s List of Strategic Enterprises and Organizations. The state holds 75.16% in the Company (through OJSC ROSNEFTEGAZ), approximately 15% of shares are in free-float, etc. Rosneft is widely engaged in exploration and production across all key hydrocarbon regions of Russia: Western Siberia, Southern and Central Russia, Timan-Pechora, Eastern Siberia and the Far East. In addition, the Company participates in several exploration projects in Kazakhstan and Algeria. Rosneft’s seven major refineries have convenient locations throughout the country, from the Black Sea coast to the Far East, and the Company’s retail network covers 39 regions of the Russian Federation. Rosneft dropped to 10th  place in the 2012 Platts rankings from ninth place in the previous year's rankings.
• Saudi Aramco -- State-owned Saudi Aramco maintains its hold on the top spot in the PIW rankings.
• Schlumberger -- Schlumberger is the world's largest oil services provider.
• Statoil -- Norwegian Statoil is an international energy company with over 35 years experience on the Norwegian continental shelf, today with operations in 34 countries. Statoil was partially privatised with listings on the Oslo and New York stock exchanges on June 18, 2001, and the company was converted from a private limited company to a public limited company. With a holding of 67% the Norwegian state is the main shareholder in Statoil.
• Tullow Oil plc -- Through successful exploration and consistent delivery of major projects Britain's Tullow has become Africa's leading independent oil company.