The U.S. Geological Survey (USGS) assessed how much undiscovered, technically recoverable conventional oil and gas may lie in the Larsen Basin, Antarctica.
Where the basin is
The Larsen Basin is the area of sediment along the eastern edge of the northern Antarctic Peninsula, bounded by:
- Joinville Island to the north;
- the Hollick-Kenyon Peninsula to the south;
- the 3,000-meter depth contour of the Weddell Sea to the east;
- the faulted eastern margin of the Antarctic Peninsula to the west.
The Larsen Basin Reservoirs assessment unit on the northern Antarctic Peninsula. USGS.
How it formed
The basin grew out of the break-up of southern Gondwana, beginning in the early Mesozoic:
| Time | What happened |
|---|---|
| Late Triassic–Early Jurassic | thermal doming above a mantle plume opened west–east rift basins, filled mostly with non-marine sediment |
| Middle Jurassic | plume-sourced volcanic rocks filled the rifts, like the Tobífera Series of Patagonia's Magallanes Basin, then next door |
| Jurassic onward | subduction of proto-Pacific crust set up strike-slip faults that separated East and West Antarctica; the growing magmatic arc left the basin as a backarc passive margin; the Weddell Sea opened in the Early Cretaceous |
| Late Jurassic–Early Cretaceous | the margin subsided, and the sea spread in: nearshore sandstones (Cape Framnes beds), then deep-water organic-rich mudstones — the Nordenskjöld Formation |
| Barremian–Coniacian | conglomerates and sandstones from the arc were swept into deep-water channels, aprons and fans — possible reservoir rocks, sealed in mudstone beside the source rocks |
| Coniacian–Eocene | the arc rose and the basin shallowed, building deltaic and nearshore sandstones of the Marambio and Seymour Island Groups |
| Eocene–Neogene | ridge subduction largely ended subduction along the peninsula's west side; the region eroded |
The petroleum system
- Source rock: mudstones of the Kimmeridgian–Berriasian Nordenskjöld Formation (also called the Ameghino Formation), which crop out along the basin's western edge — with total organic carbon up to 3.5 weight percent and hydrogen index values up to 300 mg of hydrocarbon per gram, both possibly lowered by low thermal maturity. Its thickness is unknown but at least 550 meters.
- Assumption: the source rock extends across the whole basin. There are no exploration wells, so the model rests on outcrops.
- The model: oil and gas from the Nordenskjöld moved into Lower Cretaceous deep-water conglomerates and sandstones, and perhaps into Upper Cretaceous shallow-water sandstones. Traps are mostly stratigraphic (sand sealed in mud), perhaps also structural; volcanic fragments may lower reservoir quality.
- Timing: a burial-history model of a pseudowell suggests oil generation in the Early Cretaceous and gas in the Late Cretaceous — uncertain, but pointing to more gas than oil.
- Risk: a 10-percent chance that the source rocks could not fill even one accumulation of the minimum size (5 million barrels of oil; 30 billion cubic feet of gas). The assessment unit's probability is 0.9.
| Input | Minimum | Median | Maximum | Mean |
|---|---|---|---|---|
| Number of oil fields | 1 | 20 | 80 | 22.1 |
| Number of gas fields | 1 | 50 | 200 | 55.1 |
| Oil field size (million barrels) | 5 | 8 | 300 | 13.6 |
| Gas field size (billion cubic feet) | 30 | 48 | 30,000 | 272.6 |
The estimate
Fully risked, mean undiscovered resources are:
| Resource | Mean | Range (F95–F5) |
|---|---|---|
| Oil | 269 million barrels (0.27 billion) | 0–591 million barrels |
| Gas | 14,257 billion cubic feet (14.3 trillion) | 0–37,804 billion cubic feet |
| Natural gas liquids | 439 million barrels | 0–1,160 million barrels |
F95 means a 95-percent chance of at least that much. The data and boundaries are in a USGS data release (Schenk, 2026), and more results are on the USGS Energy Resources Program site.
Sources
Based on Schenk CJ, Mercier TJ, Pitman JK, Le PA, Cicero AD, Johnson BG, Lagesse JH, Leathers-Miller HM, "Assessment of undiscovered conventional oil and gas resources of the Larsen Basin, Antarctica, 2025," U.S. Geological Survey Fact Sheet 2026–3063, U.S. Geological Survey, February 25, 2026, drawing on Macdonald and others (1988) and other published work; a work of the United States government in the public domain.
许可协议： CC0 1.0（公有领域） · 改编自 pubs.usgs.gov
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