4.5 Major oil-producing countries

18 countries believed to have had an original oil endowment exceeding 20,000,000,000 barrels. It also serves to show the concentration of world oil. These 18 countries have accounted for 86 percent of the world's oil production. They hold 94 percent of its reserves. Significantly, they are projected to have 82 percent of the world's remaining undiscovered oil resources. As can be seen, regions geologically favourable to the generation and deposition of oil are fairly rare. The 18 countries listed are estimated to have contained 89 percent of the world's original oil endowment.

Saudi Arabia

Saudi Arabia is thought to have had the largest original oil endowment of any country. The discovery that transformed Saudi Arabia into a leading oil country was the Al-Ghawār field. Discovered in 1948, this field has proved to be the world's largest, containing 82,000,000,000 barrels. Another important discovery was the Saffānīyah offshore field in the Persian Gulf. It is the third largest oil field in the world and the largest offshore. Saudi Arabia has eight other supergiant oil fields. Thus, it has the largest oil reserve in the world, not to mention significant potential for additional discoveries.

Russia

Russia is thought to possess the best potential for new discoveries. Also, it has significant reserves. Russian oil is derived from many sedimentary basins within the vast country, while Saudi Arabian fields, as well as many other Middle Eastern fields, are located in the great Arabian-Iranian basin. Russia has two supergiant oil fields, Samotlor and Romashkino. Production from these fields is on the decline, bringing total Russian oil output down with them. The best prospects for new Russian discoveries appear to exist in the difficult and expensive frontier areas.

Russian Volgo-uralskaya Neftegazonosnaya Oblast,  also called  Second Baku,  Russian Vtoroye Baku,  principal petroleum-producing region of Russia. Situated in the southern part of European Russia, it stretches from the west flank of the Ural Mountains to west of the Volga River. The largest fields are in Bashkortostan and Tatarstan and near Samara (Syzran fields), Perm, and Orenburg. Buguruslan has large natural-gas fields. Exploitation of the fields began in 1929. The name Second Baku was an allusion to the old oil fields around Baku in Azerbaijan. There are also many large oil refineries in the Volga-Ural region. A pipeline system, more than 3,000 miles (5,000 km) long, was built in 1960–64. A second parallel system having a greater diameter was constructed in the mid-1970s. It supplies the region's oil to Russian industrial centres and also connects to Poland, eastern Germany, Slovakia, Czech Republic, and Hungary.

United States, Mexico, and Canada

Basins in the United States have been intensively explored and their oil resources developed. More than 33,000 oil fields have been found, but only two are supergiants (Prudhoe Bay in the North Slope region of Alaska and East Texas). Cumulatively, the United States has produced more oil than any other country but is still considered to have a significant remaining undiscovered oil resource. Prudhoe Bay, which accounted for approximately 17 percent of U.S. oil production during the mid-1980s, is in decline. This situation, coupled with declining oil production in the conterminous United States, has contributed to a significant drop in domestic oil output.

Mexico has produced only about one-fifth of its estimated total oil endowment. With two supergiant fields (Cantarell offshore of Campeche state and Bermudez in Tabasco state) and with substantial remaining reserves and resources, it will be able to sustain current production levels well into the 21st century. Conversely, Canada, with considerably smaller oil reserves and most of its undiscovered resource potential in remote regions, is unlikely to be able to sustain current production levels beyond the 1990s. Canada's largest oil field is Hibernia, discovered off Newfoundland in 1979. This giant field has yet to be developed.