Tbilisi

Tbilisi is situated in the Achara-Trialeti mountain system, which is divided by seismoactive geological faults. Part of this system represents drainage of a sulphur water spa resort located in the central part of Tbilisi. The natural hot springs of this spa resort are connected to the outcropping Middle Eocene sediments occurring along the Mtkvari river valley with the discharge area located in the mountains to the west. Water from the springs has temperatures ranging from 40°C to 50°C and hydrogen-sulfide mineralization of 0.4-1.0 g/l. In the northwest part of the city, known as the Lisi district, several boreholes were drilled and water with temperatures ranging from 60°C to 70°C is being used for heating purposes. Future drilling is expected to exploit 30-40% of the geothermal deposit.

Three main districts are identified in the Tbilisi geothermal deposit; these are (from West to East): (1) Lisi-Saburtalo district, (2) Central - bathes or old thermal district, (3) Samgori- Sartichala district. Hydraulic connections were identified between the central and Samgori-Sartichala districts. Less clear are hydraulic connections between the Lisi-Saburtalo and other districts. Nowadays low temperature water of the Central district is used for spa and hygienic purposes. About 3,800 m3/day of the high temperature (57-74°C) waters from "Lisi" (wells 5, 7, 8) and Saburtalo (wells 1, 4, 6) are used for heating and hygienic purposes. The composition of this water is similar in all three districts: low-mineralized 0.19-0.26 g/l, alkaline, sulfate-chloride-carbonate type, containing hydrogen sulfide.

Until now, the hydrodynamic relations between these three geothermal districts ("Lisi", "central" and "oil" deposit) was not properly investigated. The absence of detailed hydrogeothermal observations makes it impossible to develop a rational environmentally reliable exploitation plan for these three deposits (Fig. 30.1).

• Boreholes under observation

© Boreholes to be observed in future

A f Border of Saburtalo / • Thermal Water Deposit t Border of Tbilisi Central I • Thermal Water Deposit

Border of I V Sartichala-Teleti Oilfield

LEGEND

Water bearing Older Quaternany deposition (loam.coarse graver) Water bearing or Older Quaternany alluvial-prolluvial deposition (loam, shingle).

Waterproof complex of deposition Oligocene olower Miocene (clay, sandstone)

Water bearing living sadi-shingles alluvial deposits

Waterproof complex lower of deposits Oligocene (clay)

Water bearing of deposits top of Eocene (sandstone, clay)

Water bearing complex tuff series of deposits medial Eocene (Tuff, tuff breccia)

• Boreholes under observation

© Boreholes to be observed in future

A f Border of Saburtalo / • Thermal Water Deposit t Border of Tbilisi Central I • Thermal Water Deposit

Border of I V Sartichala-Teleti Oilfield

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