The U.S. Geological Survey (USGS) estimates that the Niger Delta Province of Nigeria and Cameroon still holds, undiscovered, about 11.4 billion barrels of oil and 88.2 trillion cubic feet of gas that could be recovered with today's technology. The figures are means from a geology-based assessment, part of the USGS's survey of the world's petroleum resources.
How the delta was built
| When | What happened |
|---|---|
| Late Jurassic – Early Cretaceous | South America and Africa began to rift apart as Gondwana broke up, leaving a triple junction under what is now the delta |
| to the Aptian | the eastern arm failed, forming the onshore Benue Trough, which fixed the course of the River Niger; up to 2 km of sediment filled the rift, possibly including lake-bed source rocks |
| late Albian | seafloor spreading opened the central Atlantic; as the margin cooled and sank, Late Cretaceous seas flooded it and draped marine sediment over the faulted ground |
| Paleogene onward | the Niger, now draining much of central Africa, built the delta out to sea: kilometres of Akata Formation shale, then up to 3.5 km of Agbada Formation sandstone, siltstone and shale on top |
Buried fast, the Akata shales became overpressured. They formed slip surfaces and mobile shale bodies, and the delta slid seaward on them. The result is a band of extensional faults upslope and folds, anticlines and thrusts downslope.
Where the oil comes from
The deep source rocks have hardly been sampled — the sediment is up to 12 km thick — so the USGS treats everything as one Mesozoic–Cenozoic Composite Total Petroleum System. Dense faulting has mixed oils from several possible sources:
- Early Cretaceous lake shales in the old rift, known from the neighbouring West-Central Coastal Province;
- Late Cretaceous marine shales, known onshore in the Anambra Basin, whose oils resemble some Niger Delta oils;
- Akata Formation shales, the most often cited source, and a likely source of gas;
- Agbada Formation shales, proposed for oil, though probably mostly too immature.
Geochemistry points to two oils — one from a very mature marine source, one from a less mature one — mixed throughout the delta.
The reservoirs, and the two assessment units
The main reservoirs are Agbada Formation sandstones, laid down near shore, on the shelf and shelf edge, and in slope channels and deep-sea fans. They were deposited while the ground was still deforming, so sand wound its way down between thrusts and shale bodies along paths that are hard to predict. Reservoir quality is good to excellent at the depths drilled, but porosity and permeability fall with depth.
| Assessment unit | The model |
|---|---|
| Extensional Structures | oil and gas in fluvial-deltaic, nearshore, slope-channel and fan sandstones, in stratigraphic, extensional or combination traps — and possibly in Late Cretaceous sandstones beneath the delta |
| Contractional Structures | oil and gas that migrated up faults into shelf-edge, slope and stacked fan sandstones in complex structures — possibly beyond the continent–ocean boundary, where up to 3 km of delta sediment rests on oceanic crust |
The Niger Delta Province's two conventional assessment units, Extensional Structures and Contractional Structures, in Nigeria and Cameroon. Map: U.S. Geological Survey.
The estimate
| Mean | Range (F95–F5) | |
|---|---|---|
| Oil | 11,400 million barrels | 5,655 – 19,308 |
| Gas | 88,171 billion cubic feet | 42,506 – 151,464 |
| Natural gas liquids | 5,955 million barrels | 2,849 – 10,246 |
F95 is the amount with a 95 percent chance of being there, F5 the amount with a 5 percent chance.
Sources
Written from Assessment of Undiscovered Conventional Oil and Gas Resources in the Niger Delta Province of Nigeria and Cameroon, 2026, by Christopher J. Schenk, Tracey J. Mercier, Phuong A. Le, Andrea D. Cicero, Sarah E. Gelman, Jane S. Hearon, Benjamin G. Johnson, Jenny H. Lagesse and Heidi M. Leathers-Miller, U.S. Geological Survey Fact Sheet 2026–3028; a work of the United States government in the public domain. It draws on Briggs and others (2006, 2009), Haack and others (2000), Esegbue and others (2020), Doust and Omatsola (1989), Caillet and Batiot (2003), Wu and others (2015), Toyin and others (2025) and others. Full results are on the USGS Energy Resources Program site. The map is reproduced from the fact sheet.
Licence: CC0 1.0 (public domain) · Adapted from pubs.usgs.gov
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