Hydro Dynamical and Micro Temperature and Metrological Monitoring

To define hydrodynamic parameters, water levels and temperatures in wells were continuously monitored. Borehole devices [1] were used for permanent micro-temperature monitoring of wells. Accuracy of the water level monitoring device is about 0.1 cm (or pressure -1%). Four temperature sensors were installed in wells using a 200 m cable. They automatically measure water temperature with accuracy

0.5 mK. Both devices (water level and temperature) measure parameter values at

1, 2, 5, 10 and 20 min intervals and with a single battery can store data for up to 2-3 months.

Field temperature measurements were recorded in the Tbilisi geothermal wells "Lisi" 1, 2-T, and 3-T [2]. Other well measurements also were carried out under perturbed conditions (Table 30.1). A review of Mtkvari river discharge and precipitation in the recharge area revealed a temporal relation with decreasing precipitation corresponding to decreasing river stage and discharge to the Lisi well # 5 (Fig. 30.2). The decrease of Tbilisi thermal water outflow together with intensive and not correct exploitation of the wells is a result of regional climate change processes.

The exploitation of thermal waters in the Tbilisi region remains primitive; that is, hot water goes from the well to user and from the user to sewerage. Unfortunately,

Table 30.1 Temperature gradients measured in three Tbilisi geothermal wells

Well Lisi 1 Well 2 techn. Well 3 techn.

Rock age

Oligocene - 2.50

Upper Eocene 2.37 3.30

Middle Eocene 2.04 2.97

Lower Eocene 2.10 -

Average value 2.17 3.86

1.71

Variation of parameters

-Discharge m3/day of Lisi 5

-Linear (WL Mtkvari cm)

5 J-87 J-88 J-89 J-90 J-91 J-92 J-93 J-94 J-95 J-96 J-97 J-98 J-99 J-00 J-01 J-02 J-03 J-04 J-05 J-06 J-07 J-08 J-09 J-10

-WL Mtkvari cm

-Kodjori Pre mm

-Linear (Kodjori Pre mm)

— Manglisi Pre mm Linear (Discharge m3/day of Lisi 5)

Fig. 30.2 Variation of parameters

4500

m3/day

4000

3500

3000

2500

2000

1500

1000

there is no coordinated plan for optimal resource extraction and consequently water levels in wells change randomly. The lack of well monitoring and related research about hydrodynamic relations has a negative effect on its exploitation. To mitigate the decrease of pressure and water levels in wells, we propose the creation of an artificial geothermal circulation system (GCS). A GCS would prevent over exploitation of the deposit, protect the environment from pollution (bogging, thermal pollution), and decrease the amount of carbon dioxide emissions. This is particularly important as is directly connected to climate change observed in the southern Caucasus and across the world.

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