selected list of petroleum companies in alphabetical order

source: http://en.wikipedia.org/wiki/List_of_petroleum_companies

Assam Company Ltd (ACL), India
Abu Dhabi National Oil Company (ADNOC), United Arab Emirates
Alon USA, United States
Amerada Hess Corporation, United States
Anadarko Petroleum Corporation, United States
Apache Corporation, United States
Arbusto Energy, United States
Atlantic Petroleum, Faroe Islands
BG Group, United Kingdom
Bharat Petroleum Corporation Limited, India
BHP Billiton, Australia
BP, United Kingdom
Cairn Energy, India
Canadian Natural Resources, Canada
Chevron Corporation, United States
Citgo, Venezuela
CNOOC Ltd., China
ConocoPhillips, United States
Cosmo Oil Company, Japan
Crown Central Petroleum, United States
Cupet, Cuba
Devon Energy, United States
Ecopetrol, Colombia
Enbridge, Canada
EnCana, Canada
ENSCO International, United States
Eni, Italy
Essar oil ltd.,India
Entreprise Tunisienne d'Activites Petroliere (ETAP), Tunisia
ExxonMobil, United States
Galp Energia, Portugal
Petronet LNG Limited, India
Gujarat Gas Co. Ltd., India
Gujarat State Petroleum Corporation, India
Gulf Oil, Luxembourg
Grupa LOTOS, Poland
Hellenic Petroleum, Greece
Hindustan Petroleum Corporation Ltd, India
Husky Energy, Canada
IB Daiwa, Japan
Imperial Oil, Canada
INA - Industrija Nafte, Croatia
Indian Oil Corporation, India
Inpex, Japan
Irving Oil, Canada
Japan Energy, Japan
Kerr-McGee, United States
Koch Industries, United States
Kuwait German Petroleum Company, Canada
LUKoil, Russia
Marathon Oil Corporation, United States
Maxol Group, Republic of Ireland
MedcoEnergi, Indonesia
Mol Group, Hungary
Naftna Industrija Srbije, Serbia
Naftohaz Ukrainy, Ukraine
National Iranian Oil Company (NIOC), Iran
National Oil Corporation, Libya
Neste Oil, Finland
Nippon Oil, Japan
NNPC,Nigeria
Northern Resources[1],Canada
Oil & Gas Development Company Limited[2], Pakistan
Occidental Petroleum
Oil India Limited, India
Oman Oil Company (OOC), Oman
OMV, Austria
ONGC, India
PKN Orlen S.A., Poland
PSO, Pakistan
Petróleos de Venezuela, Venezuela
Petroleos Mexicanos, Mexico
Petro-Canada, Canada
Petrobras, Brazil
PetroChina, China
PetroKazakhstan, Canada
Petrom, Romania
Petron Corporation, Philippines
PETRONAS, Malaysia
PETROTRIN, Trinidad and Tobago
Pertamina, Indonesia
Polish Oil and Gas Company, Poland
Qatar Petroleum, Qatar
Reliance Industries Limited, India
Repsol YPF, Spain
Rompetrol Group N.V., Romania
Royal Dutch Shell, Netherlands, United Kingdom
San-Ai Oil, Japan
Santos Limited, Australia
Sasol, South Africa
Saudi Aramco, Saudi Arabia (the largest in the world)
Shell Canada, Canada (subsidiary of Royal Dutch Shell)
Shell Oil Company, United States (subsidiary of Royal Dutch Shell)
Sinclair Oil, United States
Sinopec, China
Snpc, Congo-Brazzaville
Sonangol, Angola
Sonatrach, Algeria
SPC, Singapore
StatoilHydro, Norway
State Oil Company of Azerbaijan, SOCAR Azerbaijan
Sunoco, United States
Suncor Energy, Canada
Surgutneftegaz, Russia
Syncrude, Canada
Talisman Energy, Canada
Todd Energy, New Zealand
Total, France
United Refining Company, United States
Vaalco Energy Inc., United States
Wintershall, Germany
Woodside Petroleum, Australia
YPFB, Bolivia
YUKOS, Russia