List of Oil Exploration Companies

Canada
Canadian Natural Resources Limited
Encana
Husky Energy
Imperial Oil
Laricina Energy
Nexen
Pacific Rubiales Energy
PetroKazakhstan
Suncor Energy
Syncrude
Talisman Energy

U.S.A.
Anadarko Petroleum Corporation
Apache Corporation
Chevron Corporation
ConocoPhillips
Devon Energy
Ensco International
ExxonMobil
Greka Energy
Hess Corporation
HKN, Inc.
Koch Industries
Marathon Oil
Murphy Oil
Occidental Petroleum
Plains Exploration & Production
Sovereign Group
Vaalco Energy
XTO Energy

Austria - OMV

Bulaeria - Petrol AD

Croatia - INA Industrija Nafte

Czech Republic - Moravské naftové doly

Denmark
DONG Energy
Maersk Oil

Faroe Islands - Atlantic Petroleum

France - Total S.A.

Germany
RWE Dea
Wintershall

Greece - Hellenic Petroleum

Hungary - MOL Group

Italy - Eni

Moldova - Ascom Group

Netherlands / UK - Royal Dutch Shell

Norway
DNO International
Statoil

Poland
Grupa Lotos
PGNiG
PKN Orlen

Portugal - Galp Energia

Romania
Petrom
Rompetrol

Russia
Bashneft
Gazprom Neft
Lukoil
Rosneft
Russneft
Sibir Energy
Surgutneftegas
Tatneft
TNK-BP

Serbia - Naftna Industrija Srbije

Spain
Compañía Española de Petróleos
Repsol YPF

Turkey
Türkiye Petrolleri Anonim Ortakligi
Çalik Enerji

Ukraine - Ukrnafta

UK ( United Kingdom)
BG Group
BP
Cairn Energy
Perenco
Premier Oil
Salamander Energy
Tullow Oil

Azerbaijan
Azerbaijan International Operating Company
State Oil Company of Azerbaijan Republic

Bahrain - Bahrain Petroleum Company
Burma - Myanma Oil and Gas Enterprise

China
CNOOC
PetroChina
Sinopec

India
Gujarat State Petroleum Corporation
Indian Oil Corporation
Oil and Natural Gas Corporation
Oil India
Reliance Industries

Indonesia
MedcoEnergi
Pertamina

Iran
National Iranian Oil Company

Iraq
North Oil Company
South Oil Company
Missan Oil Company
Midland Oil Company

Israel
Delek Group
Isramco

Japan
Inpex
JAPEX
Nippon Oil

Kazakhstan - KazMunayGas

Kuwait - Kuwait Oil Company

Malaysia - Petronas

Oman - Petroleum Development Oman

Pakistan
Oil and Gas Development Company
Pakistan Petroleum
Pakistan State Oil
Mari Gas Company

Qatar - Qatar Petroleum

Saudi Arabia
Saudi Aramco
AOCE - Saudi

Singapore - Singapore Petroleum Company

Sri lanka - Ceylon Petroleum Corporation

South Korea - Korea National Oil Corporation

Thailand - PTT Public Company Limited

United Arab Emirates
ADNOC
ENOC

Vietnam
Petrovietnam
Vietsovpetro

South and Central America
Oil Exploration and Production Companies

Brazil
OGX
Petrobras

Argentina
Bridas Corporation
Enarsa
Pluspetrol
YPF

Bolivia
YPFB

Chile
Empresa Nacional del Petróleo

Colombia
Meta Petroleum Ltd
Ecopetrol

Cuba
Cupet

Ecuador
Petroecuador

Mexico
Petróleos Mexicanos

Peru
Petroperú

Trinidad and Tobago
Petrotrin

Uruguay
ANCAP

Venezuela
Petróleos de Venezuela

Australia and Oceania / Oil Exploration and Production Companies

Australia
BHP Billiton
Santos
Woodside Petroleum
Todd Energy

Africa Oil Exploration and Production Companies

Algeria - Africa Sonatrach

Angola - Sonangol Group

Cango - National Petroleum Company of the Congo

Egypt - Vegas Oil and Gas

Libya
Arabian Gulf Oil Company
National Oil Corporation

Nigeria - Nigerian National Petroleum Corporation

South Africa - Sasol

Sudan - Sudapet

Tunisia - Entreprise Tunisienne d'Activites Petroliere

Madagascar - Madagascar Oil

OIL EXPLORATION.
In the early days of petroleum prospecting in Texas most oil finds were the result of digging or drilling near known oil and gas seeps, as Lyne T. Barret did in 1866 at Oil Spring in Nacogdoches County, or of accidental finds while drilling for water, as with George Dullnig's 1886 strike in Bexar County or the discovery of oil in Corsicana in 1894. Because of abundant seeps, guesswork and good luck were sufficient for finding oil.

Most prominent salines and salt domes had been recorded by the 1890 Geological Survey of Texas but did not necessarily become the focal point of oil exploration due to numerous unexploited seeps. Amateurs in geology, such as Pattillo Higgins, used geological hunches and knowledge of existing seeps to promote drilling for oil at Spindletop in 1901. At Batson in 1903, the Paraffin Oil Company, another group of amateurs, founded their venture on petroleum residue in soil samples collected from near a gas spring.

This was the first time that "paraffin dirt" was used in prospecting for oil.
Despite these finds, oil companies generally held the use of geology in low regard prior to the 1920s, when geophysical methods of exploration that enhanced the oil prospector's knowledge of subterranean strata began demonstrating an advantage for finding oil. Tools used by oil and gas explorers were fairly basic and depended on fundamental variables in the earth's physical condition: gravity change, magnetic field change, time change, and electrical resistance.

The most common gravitational instrument in use today is the gravity meter or gravimeter,
which measures variations in the earth's gravitational field by the gravitational pull on a mass balanced against some form of elastic force. Gravimeters were built as early as 1899 but did not prove effective until the mid-1930s when O. H. Truman used one to find the Tom O'Connor field in South Texas for the Humble Oil and Refining Company in 1934. Ship-borne gravity meters played a valuable role in marine exploration, and air-borne gravity meters received attention in research.

Second method of oil exploration is the Magnetic method.
Most oil occurs in sedimentary rocks that are nonmagnetic. Igneous and metamorphic rock rarely contain oil and are highly magnetized. By conducting a magnetic survey over a given area, a prospector can determine where oil-bearing sedimentary rock is more likely to be found. Two types of magnetic instruments are used to measure the slight difference in magnetism in rocks, the field balance and the airborne magnetometer. The field balance is used on the earth's surface to measure magnetism in specific locations. The airborne magnetometer is used to measure the magnitude of the earth's total magnetic field over a large area. A magnetometer was used to define the serpentine plug on which the Yoast field in Bastrop County was discovered in 1927.

Third method of oil exploration is the seismic method.
The central physical property upon which seismic prospecting is established is the variation in speed of the transmission of elastic earth waves or sound waves through different geological structures measured by time. There are two principle seismic methods: refraction and reflection. Refraction prospecting consists of elastic earth waves, initiated by some concussive force, traveling down to a dense or high velocity bed, then being carried along that bed until they are rerefracted up to seismic detector locations on the surface some distance from the shot point. What is recorded is the time required for the sound wave to reach each detector location from the shot point. The speed of transmission of the waves through different geological structures is proportional to the density or compactness of the formation. Unconsolidated formations such as sands and shales transmit waves with a low velocity, weak sandstones and limestones with higher speeds, and massive crystalline rocks such as limestones, rock salt, schists, and various igneous rocks with very high speeds. The refraction method aided petroleum explorers in locating salt domes that transmitted elastic earth waves at high rates of speed.

December 7, 1919,
Mintrop filed for a German patent on his refraction profiling seismic method, but the patent was not confirmed until 1927 after Mintrop had already received a United States patent for it. Mintrop's instrument prompted the founding in April 1921 of Seismos Gesellschaft, which did seismic prospecting in East Texas and the Texas Gulf Coast from 1923 to 1925. Because of difficulty in determining breaks in the velocity of sound waves between different layers along the Gulf Coast, it was difficult to determine the depth of the layers. The maximum effective depth of refraction surveying by Seismos's crews was 2,500 feet.