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Oil and Gas Resources of the Fergana Basin (Uzbekistan, Tadzhikistan, and Kyrgyzstan)
https://doi.org/10.2172/10103777
Highlights
- Temperature gradient fitted to reservoir data through 1987: 22.05 °C per km, with a surface temperature of about 20 °C. Heafford and Lichtman (1993) give 25–30 °C per km for the basin.
- Mingbulak well No. 3: 145 °C measured at 5,385 m, against 139 °C from the basin-wide fit. Other estimated and measured oil-reservoir temperatures at Mingbulak are about 287–320 °F.
- Mingbulak reservoir pressures in well No. 3: 127 MPa at about 5,245 m and 108 MPa at 5,899 m, gradients of about 0.806–1.068 psi/ft, near twice the normal 0.433 psi/ft. Gumkhana field: about 71 MPa at about 3,600 m.
- Overpressure appears to begin at about 3,658 m (12,000 ft).
- Average reservoir depth: 988 m on the south flank south-west of Fergana, 3,723 m in the central graben and 5,649 m at Mingbulak. Average reservoir porosity: 16.2% for the basin, from 13.4% on the north flank to 18.7% south-west of Fergana.
- Porosity and permeability: Bajocian (Jurassic) sandstones 16–22% and 100–500 mD; Cretaceous reservoirs 6–24% and tens to several thousand mD; Paleogene zone V limestone 6–30% and 50–600 mD.
Summary
A 1995 assessment of oil and gas in the Fergana basin, which Uzbekistan, Tajikistan and Kyrgyzstan share. It is built on reservoir-level data for 177 reservoirs in 53 fields, through 1987. Many gaps in the source data were filled with estimates, and the authors do not claim the data are accurate.
The basin is about 300 km long and 175 km wide. Its central graben is bounded by high-angle reverse faults and filled with thick Neogene and Quaternary clastic sediments. Paleozoic basement lies at about 10 km in the middle of the graben. More than 30 pay zones, numbered I to XXXII, run from the Permian–Triassic to the Neogene.
A straight line fitted through reservoir temperatures gives a gradient of 22.05 °C per km from a surface temperature of about 20 °C. Overpressure appears to begin at about 3,658 m; the wells below that depth are mainly in the central graben. The deepest data come from the Mingbulak field there, the site of a large oil blowout in 1992.
How to cite
J. S. Sanders, G. R. Long and J. W. Clarke (1995). Oil and Gas Resources of the Fergana Basin (Uzbekistan, Tadzhikistan, and Kyrgyzstan). Energy Information Administration, Office of Oil and Gas, report DOE/EIA-TR/0575. https://doi.org/10.2172/10103777