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Petroleum Geology and Resources of the North Ustyurt Basin, Kazakhstan and Uzbekistan
https://doi.org/10.3133/b2201D
Highlights
- Basin area about 250,000 km², mostly onshore; Jurassic–Tertiary rocks several hundred metres to 5 km thick.
- Basement at 5.5–8 km in the southern zone of uplifts and 9–11 km in the northern zone (Beyneu, Sam and Kosbulak depressions).
- Top of the Jurassic at 2–2.5 km in the south and 3–3.5 km in the north of the uplifted zones, and at 4–4.5 km in the northern depressions, where the base of the Jurassic is at 5 km and deeper.
- Cretaceous rocks up to 2,600 m thick in the Kosbulak depression and 1,200–1,400 m on the crests of the southern uplifts; Lower–Middle Jurassic rocks more than 1,000 m thick in depressions.
- Middle Jurassic sandstones below 2,500 m: porosity 8–14%, permeability a few to several tens of mD. Callovian reservoir: 16–18% and up to 100 mD. Eocene sandstones at a few hundred metres: porosity commonly above 30%.
- Carboniferous carbonate reservoirs are fractured and leached limestones; below the weathered zone the rock matrix has 1–3% porosity and negligible permeability.
Summary
A US Geological Survey assessment of the petroleum geology of the North Ustyurt basin, a triangular basin between the Caspian Sea and the Aral Sea in Kazakhstan and Uzbekistan. It covers about 250,000 km², mostly onshore, on the northern Ustyurt Plateau and the lowlands next to it.
Jurassic to Tertiary, mostly clastic rocks, several hundred metres to 5 km thick, fill a gentle sag over older Devonian to Triassic rocks. The basement lies at 5.5 km on the highest uplifts and at 11 km in the deepest depressions. Oil pools in Jurassic sandstones lie at 2.5–3 km; gas fields in Eocene sandstones lie only a few hundred metres down.
Reservoir quality falls with depth: Middle Jurassic sandstones below 2,500 m are poor, while the shallow Eocene sandstones are excellent. The Paleozoic and Triassic rocks beneath are poorly known, and only a few wells reach them. The report gives no temperature or formation-water data.
How to cite
G. F. Ulmishek (2001). Petroleum Geology and Resources of the North Ustyurt Basin, Kazakhstan and Uzbekistan. U.S. Geological Survey Bulletin 2201-D, version 1.0. https://doi.org/10.3133/b2201D