World Petroleum Geography

World Agriculture, Resources and Trade already covers the exam's central petroleum fact, that the Middle East holds close to half of world proven reserves while the United States is today's leading producer, plus OPEC's own founding details. This note does not repeat either; it covers the specific named oil fields and basins behind those national-level rankings, exactly the kind of place-name detail a dedicated petroleum chapter adds on top of the production statistics.

The world's largest conventional field: Ghawar

Ghawar, in Saudi Arabia's Eastern Province, is by a wide margin the largest conventional oil field ever discovered, an elongated field roughly 280 km long, discovered in 1948 and brought into production in 1951. Ghawar alone has supplied a very large share of Saudi Arabia's own output ever since, and by some estimates still accounts for something in the region of six percent of daily global oil production from a single field, which is the underlying geological reason Saudi Arabia has been able to sit at the centre of OPEC's own output decisions for decades: no other country's production is anchored so heavily in one field of this scale.

The Permian Basin: how shale changed the production leaderboard

The Permian Basin, spanning West Texas and south-eastern New Mexico in the United States, is the specific place behind the shift already flagged in the world-agriculture note, that the United States overtook Saudi Arabia and Russia in current oil production despite holding nowhere near their share of proven reserves. The Permian is the largest oil-producing shale region in the United States, now accounting for close to two-fifths of the country's total oil output, and its rise reflects the maturing of hydraulic fracturing (fracking) and horizontal drilling technology applied to shale rock, a source of oil that was known to exist for decades but was not commercially extractable at scale until this technology matured, exactly the "production reflects technology and investment, not just what is geologically present" distinction the reserves-versus-production gap depends on.

Other named producing regions

The North Sea, shared mainly between the United Kingdom and Norway, was the region that transformed both countries into significant oil producers from the 1970s onward, and Brent crude, named after a North Sea oil field, remains one of the world's key benchmark prices for crude oil even as North Sea output itself has declined from its peak. Russia's own reserves are anchored heavily in the West Siberian Basin, its largest and most productive petroleum province, alongside newer development further east. The Gulf of Mexico anchors a large share of United States offshore production, complementing the country's own onshore shale output from the Permian and other basins.

Quick revision points

• Ghawar (Saudi Arabia, discovered 1948): the largest conventional oil field in the world, historically anchoring Saudi Arabia's central role in OPEC's output decisions.
• Permian Basin (West Texas/south-eastern New Mexico, USA): the country's largest shale oil region, close to two-fifths of US output; its rise via fracking and horizontal drilling technology is the specific story behind the United States overtaking Saudi Arabia and Russia in production despite trailing badly in reserves.
• North Sea (UK/Norway): transformed both into major producers from the 1970s; Brent crude, a key world benchmark price, is named after a North Sea field.
• Russia's reserves are anchored in the West Siberian Basin; US offshore production concentrates in the Gulf of Mexico.
• For reserves-versus-production country rankings and OPEC's founding facts, see World Agriculture, Resources and Trade, which already covers this chapter's statistics half.