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Hydrogeological criteria for zonal and local forecasts of the oil and gas potential of the Jurassic deposits of Ustyurt
Гидрогеологические критерии зонального и локального прогнозов нефтегазоносности юрских отложений Устюрта
- Institute of Geology and Exploration of Oil and Gas Fields (IGIRNIGM), Tashkent, Uzbekistan
Highlights
- Salinity of Jurassic formation water: 40 g/L (Central Ustyurt uplift) to 220 g/L (Assake-Audan trough); chloride–calcium type.
- Geothermal gradient: 2.5 °C/100 m on uplifts; 3.5–4.3 °C/100 m in the axial parts of troughs.
- Maximum temperature of Jurassic water: 140 °C in the Barsakelmes trough; up to 120 °C in the North Ustyurt and Assake-Audan troughs.
- Dissolved gas mostly nitrogen–methane, usually up to 600 cm³/L; 1,660 cm³/L at Alambek.
- Shakhpakhty: methane 90% and its homologues 3.4% in dissolved gas; gas pressure 10.64 to 12 MPa up the section.
Keywords
- Ustyurt
- Jurassic
- formation water
- geothermal gradient
- brines
- Barsakelmes trough
- Karakalpakstan
Summary
The authors, of the Institute of Geology and Exploration of Oil and Gas Fields (IGIRNIGM), sum up the hydrogeological data on the Jurassic rocks of Ustyurt. Jurassic formation water is fairly uniform: salty chloride–calcium water with a salinity from 40 g/L on the Central Ustyurt uplift to 220 g/L in the Assake-Audan trough. Its metamorphism usually rises with salinity, and the water is ancient sedimentary water, except for freshened zones on the uplift.
Water pressure in the Jurassic complex is highest in the centre of the Barsakelmes trough and the east of the Aktumsuk uplift, and lowest around the Batpak swell and the Shordzha uplift. Less marked lows occur on the Karabaur, Terenkuduk-Kharoy and Bayterek swells. The authors describe the water exchange as elisional, driven by compaction, with possible discharge of Jurassic aquifers in the Aktumsuk and Central Ustyurt dislocation systems, under the Aral Sea and along faults of the Batpak swell and the Shordzha uplift.
The geothermal gradient in the sedimentary cover rises from 2.5 °C/100 m on the uplifts to 3.5–4.3 °C/100 m in the axial parts of the troughs. Jurassic water is hottest in the troughs: 140 °C in the Barsakelmes trough and up to 120 °C in the North Ustyurt and Assake-Audan troughs. Dissolved gases in the Jurassic water are mostly nitrogen–methane, usually no more than 600 cm³/L; at the Alambek area gas content reaches 1,660 cm³/L, and at the Shakhpakhty field the gas pressure rises upwards through the section from 10.64 to 12 MPa. The authors list the Agyin, Ayzhankos, Chibelli, East Kuanysh, Adzhibay, Assake-Audan and Takhtakair structures as first targets for oil and gas exploration.
How to cite
Kh. N. Musaev, T. I. Mumindzhanov, Sh. T. Akhmedov, Sh. Kholmirzaev, M. Sh. Dusanov and Kh. F. Khudoyberdiev (2008). Hydrogeological criteria for zonal and local forecasts of the oil and gas potential of the Jurassic deposits of Ustyurt. O‘zbekiston neft va gaz jurnali (Uzbek Journal of Oil and Gas), No. 4, 2008, pp. 11–13. https://drive.google.com/file/d/1Fin6Cp-v-eVHISg8qMXcGpbOWPswWy-4/view