The U.S. Geological Survey's 2024 assessment of the northern Arabian Peninsula puts the oil and gas still to be found there at a mean estimate of 5.1 billion barrels of oil and 19.5 trillion cubic feet of gas in conventional fields not yet discovered. Most of the oil would be in Mesopotamia; nearly half the gas would be in the oldest, Paleozoic rocks.
| Resource | Mean estimate | Range (F95–F5) |
|---|---|---|
| Oil | 5.1 billion barrels (5,086 million) | 1,438 – 12,016 million barrels |
| Natural gas | 19.5 trillion cubic feet (19,546 billion) | 6,941 – 41,349 billion cubic feet |
| Natural gas liquids | 0.7 billion barrels (735 million) | 281 – 1,460 million barrels |
These are technically recoverable resources — what today's methods could extract — in conventional traps, before any judgement about cost. F95 has a 95 percent chance of being met or exceeded, F5 a 5 percent chance.
Four chapters of rock
The oil and gas come from source rocks laid down in four very different settings, each a stage in the break-up of the old southern supercontinent, Gondwana.
| When | What happened | Source rock it left |
|---|---|---|
| Ordovician–Silurian | Ice sheets covered much of Arabia and North Africa. As they melted, they left networks of channels that the sea then filled with organic-rich mud | Silurian Qusaiba Formation — the source of most of the oil and gas in the north of the peninsula |
| Late Permian – Late Triassic | Gondwana began to split. Rifting opened the northeast–southwest Palmyride and Sinjar troughs | organic-rich Triassic sediments laid down in the rifts |
| Early Jurassic – Late Cretaceous | Gondwana's eastern edge sank slowly as a passive margin, building broad carbonate platforms with basins between them | marls of the Jurassic Sargelu, Tuwaiq Mountain, Naokelekan and Hanifa formations and the Cretaceous Kazhdumi Formation — the most important sources in the east of the peninsula |
| Late Cretaceous | The crust was pulled apart at an angle, perhaps over a mantle plume, opening the northwest–southeast Euphrates trough and cutting the older Palmyride and Sinjar troughs in two | Upper Cretaceous rift shales |
Later, the building of the Zagros Fold Belt shaped the structural traps of the two Mesopotamian units. The USGS treats all of this as one Paleozoic–Mesozoic Composite Total Petroleum System.
Eight assessment units
| Unit | What it is | Mean oil (million bbl) | Mean gas (billion ft³) |
|---|---|---|---|
| Mesopotamian Foredeep | clastic and carbonate reservoirs in basement-related structures formed with the Zagros Fold Belt; Jurassic and Cretaceous sources | 2,420 | 5,016 |
| Mesopotamian Basin Anticlines | as above | 1,707 | 2,090 |
| Euphrates Graben | clastic reservoirs in rift structures, fed by the Upper Cretaceous rift shales | 559 | 1,075 |
| Northern Arabia Paleozoic | Paleozoic reservoirs fed by the Qusaiba, now mature enough to make gas | 130 | 8,935 |
| Palmyride Fold Belt | Triassic rift sources and reservoirs in structural traps | 100 | 1,933 |
| Sinjar Fold Belt | as for the Palmyrides | 101 | 275 |
| Aleppo Platform | Qusaiba-sourced, gas-mature | 57 | 221 |
| Southeast Turkey Thrust Belt | Qusaiba-sourced, gas-mature; no gas fields expected | 12 | 1 |
Gas figures add the gas in oil fields to the gas fields.
The two Mesopotamian units account for about four barrels in every five. The single largest gas prospect is the Paleozoic unit, with almost 9 trillion cubic feet. The inputs show why: it could hold up to 180 undiscovered gas fields, more than twice as many as any other unit.
Sources
Written from Assessment of Undiscovered Conventional Oil and Gas Resources of the Northern Arabian Peninsula, 2024, USGS Fact Sheet, by C.J. Schenk and the USGS Northern Arabian Peninsula Assessment Team, a work of the United States government in the public domain. Full input data are in Schenk (2025); more results are on the USGS Energy Resources Program site.
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