Temperature field study of fractured hydrothermal reservoirs in SE Bulgaria (Bourgas basin)

Klara Bojadgieva(1), Vladimir Hristov(1), Bozhidar Srebrov(2)

(1)Geological Institute, Bulgarian Academy of Sciences, Acad.G.Bonchev bl. 24, 1113 Sofia

(2)Geophysical Institute, Bulgarian Academy of Sciences, Acad.G.Bonchev bl. 3, 1113 Sofia

(Received 16 January 2006; accepted 14 February 2007) 

Abstract: Fractured type hydrothermal reservoirs are not well studied in Bulgaria compared to porous ones in terms of hydrogeological parameters and structure of the water permeable zones. The subject of this study are three thermal water reservoirs located in the region of SE Bulgaria (Bourgas basin) Poljanovo, Aitos and Sadievo. A summary of the existed geological and hydrogeological data for the three reservoirs is done and their major characteristics water temperature, flow rate, temperature-depth profiles measured in the wells and thermal capacity of the reservoirs are discussed. Maps of temperature distribution at three depth levels below the surface 50m, 100m and 200 m have been drawn up. They are analyzed together with another two maps - of water temperature measured at the wellhead and calculated maximum reservoirs temperature based on geochemical thermometers.  Zones of high temperature anomalies have been traced in depth and a sub vertical water movement to the surface has been confirmed. The existed thermal water application in the three reservoirs is also discussed.