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The New Water Supply Of The Baku City -- The Hydro Geological Particularities And Exploitation Specialties Of Oguz Ground-water Field

Congress: 2015
Author(s): Elkin Rustamov (Baku, Azerbadijan)

Keyword(s): Sub-theme 2: Surface water and groundwater,

One of the greatest water intake facility in the world has been constructed in the distance of 260 km to the north-west in Oguz field of Azerbaijan with the aim of water supply of the Baku city. The water intake facility consists of 78 water wells with the depth of 150-170m and with the productivity 5m3/sec. The wells have been installed along 2 lines in parallel way with the length of 18 km with the distance of 1000 m between each one.

The Alazan-Ayrichay lowland where the Oguz field is situated is the biggest ground-water basin in the Southern Caucasus. Having the width of 12-15 km this basin is stretched to the distance of 270 km between southern downhills of the Great Caucaus mountain range and Ajinohur neogen highland. From the geological point of view the Alazan-Ayrichay lowland was appeared in the result of cone mixing the sediments of the rivers flowing down the Great Caucasus mountain range. According to the result of the geophysical observations the width of alluvial-deluvial depositions is 1500-2000m. The river net which has a great importance in the supply of ground-water has a high density pointing 0,5 km/km2. The annual amount of atmospherical precipitation is 800-900mm and annual average of evaporation is 400-600mm. Together with the big amount of precipitation the compact hydrographical net has supported favourable conditions for forming the big underground residue of a high quality. According to the balance calculating the ground-water resources are over 70m3/sec.

The particularity of the hydrogeological condition of the Alazan-Ayrichay lowland is in absence of the possible regional drainage for the strong ground-water flow which takes its beginning from the mountaineous sides of the Great Caucasus and this subsurface flow gets stuck on the heavy impremeable layer in down side of the fold of neogen highland. Because of the absence of water drainage the ground-water flow gets high pressure.

The excessive pressure of ground-water, short and fine grained fracture predomination in lithological section support which calls developing dangerous erosion process during drilling.

During drilling the water wells the pressure of ground-water blow-out and strong erosion process start since the opening pressure wellhead . Prevention of these issues became possible by means of increasing the special weight of drill mud up to 1,8-2,2g/cm3 Exploration process has also met serious problems after the water wells drilling. Very dense drill mud inside of borehole doesn't let fill the gravel in the annular space after productive pipes installation. Due to this result it's needed to decrease the weight of drill mud down to 1,30-1,35 g/cm3. In the condition when the special weight of drill mud is less the ground-water flow released of the drill mud resistance tries to flow out the ground surface by means of the inner side of productive pipe and annular space very fast. In this case the water flow pressure does not let fill the gravel in annular space in the water wells where the water discharge is 150-250lt/sec the filled gravel is blown out back by water flowing from the well so after some period the water well becomes idle. In order to prevent this process mud the special weight of drill mud in the lighter drill has been gradualy decreased down to the weight.During the process exploitation of prevention of erosion process became possible at gravel caliber of 2-5mm.

At present the water intake facility operates in non-stop way with the productivity of 5m3/sec and the operation of the facility is kept under total control by means of the installed SCADA system.

1. Геология Азербайджана Том VIII Гидрогеология и Инженерная. Изд. “Nafta-Press”, Bakı-2008

2. Алекперов.А.Б. Ожидаемые изменения геоэкологической ситуации под влиянием крупного отбора подземных вод в Алазань- Агричайской долине Азербайджана - Ресурсы подземных вод “Mатериалы Международной научной конференции, Москва, 13-14 мая 2010г, стр.128-133”



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