Etwas zu verbessern? Schlag eine Änderung vor.
Using a geology-based assessment, the U.S. Geological Survey has estimated the undiscovered, technically recoverable shale oil and shale gas in five basins of northern Africa — the Berkine, Illizi, Hamra, Murzuq and Erdis Kufra Basins. The mean estimates are 2.4 billion barrels of oil, 65.4 trillion cubic feet of gas and 2.2 billion barrels of natural gas liquids.
The seven shale-oil and shale-gas assessment units in the Berkine, Illizi, Hamra, Murzuq and Erdis Kufra Basins. Map: U.S. Geological Survey.
How the basins formed
| When | What happened |
|---|---|
| Early Paleozoic | northern Africa was a passive margin, with rivers flowing north to the paleo-Tethys Ocean |
| Ordovician | meltwater from continental glaciers cut a series of north-trending valleys |
| Early Silurian | a major transgression filled them with organic-rich sediment |
| Late Devonian | a second transgression laid organic-rich shale across the margin |
| Late Carboniferous to Permian | the Hercynian orogeny deformed the margin into the five basins and the uplifts between them |
Uplift and erosion stripped most of the Silurian and Devonian source rocks from the uplifts but largely preserved them in the basins. Differences in uplift and erosion left the source rocks at varying thermal maturity across the basins.
The source shales
| Lower Silurian shales | Devonian shales | |
|---|---|---|
| Total organic carbon (TOC) | up to 20% | up to 14% |
| Hydrogen index (mg of hydrocarbon per g of TOC) | up to 380 | up to 580 |
| Thickness | up to 100 m | up to 200 m |
Each assessment unit was drawn where the shales hold at least 2 weight percent TOC, are more than 10 m thick, and lie in the right thermal maturity window for oil or gas.
How the oil and gas formed
Oil was generated from the Silurian and Devonian shales — in some basins possibly as early as the Carboniferous — and gas possibly in the Mesozoic. Depending on burial and heat, some of the oil in the shale cracked to gas, and part of the oil and gas stayed in the shales as shale-oil and shale-gas accumulations.
- The Murzuq and Erdis Kufra Basins are thought to hold shale oil, because their rocks reached only the threshold for oil generation.
- In the Berkine and Illizi Basins, gas from cracked oil was partly retained in the Devonian shales as shale gas.
The assessment units and their inputs
The USGS defined seven total petroleum systems and seven assessment units, each given a probability of 1.0. For all of them the area is entirely untested (100%), and the success ratio runs from 10% to 90% (mode 50%).
| Assessment unit | Mean potential production area (acres) | Average drainage area (acres, mean) | Average estimated ultimate recovery (mean) |
|---|---|---|---|
| Berkine Basin Silurian Shale Gas | 5,157,333 | 120 | 0.447 BCFG |
| Illizi Basin Silurian Shale Gas | 10,816,333 | 120 | 0.447 BCFG |
| Hamra Basin Silurian Shale Gas | 12,392,900 | 120 | 0.447 BCFG |
| Murzuq Basin Silurian Shale Oil | 1,692,133 | 93.3 | 0.049 MMBO |
| Erdis Kufra Basin Silurian Shale Oil | 7,707,100 | 93.3 | 0.049 MMBO |
| Berkine Basin Devonian Shale Gas | 5,728,467 | 120 | 0.447 BCFG |
| Illizi Basin Devonian Shale Gas | 928,800 | 120 | 0.447 BCFG |
BCFG: billion cubic feet of gas. MMBO: million barrels of oil.
The results
Mean undiscovered resources, fully risked:
| Assessment unit | Type | Oil (MMBO) | Gas (BCFG) | Natural gas liquids (MMBNGL) |
|---|---|---|---|---|
| Berkine Basin Silurian Shale Gas | gas | — | 9,495 | 380 |
| Illizi Basin Silurian Shale Gas | gas | — | 19,907 | 438 |
| Hamra Basin Silurian Shale Gas | gas | — | 22,717 | 908 |
| Murzuq Basin Silurian Shale Oil | oil | 435 | 174 | 0 |
| Erdis Kufra Basin Silurian Shale Oil | oil | 1,976 | 792 | 3 |
| Berkine Basin Devonian Shale Gas | gas | — | 10,564 | 423 |
| Illizi Basin Devonian Shale Gas | gas | — | 1,721 | 38 |
| Total | 2,411 | 65,370 | 2,190 | |
| Range, F95 to F5 | 385–6,590 | 13,342–155,311 | 434–5,283 |
F95 is the amount with a 95 percent chance of being there, F5 the amount with a 5 percent chance. More results are on the USGS Energy Resources Program website.
Sources
Based on Assessment of undiscovered shale-oil and shale-gas resources in the Berkine, Illizi, Hamra, Murzuq, and Erdis Kufra Basins of northern Africa, U.S. Geological Survey Fact Sheet 2026–3021, by the Northern Africa Basins Assessment Team (Michael E. Brownfield and others), U.S. Geological Survey; a work of the United States government in the public domain. The source's misspelling "Sillurian" is corrected.
Lizenz: CC0 1.0 (gemeinfrei) · Bearbeitet nach pubs.usgs.gov
1
0
0
0
Kommentare
