| Abstract |
The paper presents and describes the utilization of geothermal water for house heating in the town of Siglufjörður, North Iceland. At present two geothermal fields are utilized by the district heating system, Skútudalur and Skarðsdalur. Exploration drilling in Skútudalur began in 1964 with one shallow well. In 1969 to 1971 five more wells were drilled with the depth range 300 to 500 m. In 1975 a deep well was drilled, and the first houses were connected to the district heating system in December 1975. New wells were drilled for more water during 1976 to 1983. The inlet temperature from the first wells was about 65°C but increased to about 70°C with later wells. Relatively scarce data is available on temperatures, flow rate, drawdown, etc., from the first few years of operation but since about 1985 good production data is available as well as chemical data. The reservoir is rather limited in size and small changes in production cause rather great changes in the water level. The monitoring data has been used to develop a reservoir model to simulate the water-level data and to predict future changes. In 2006 to 2008 Vegagerðin (Icelandic Road Administration) build a road tunnel through the mountains adjacent to the geothermal system. The geothermal system resides within these mountains. During the tunnelling several fractures were encountered with water temperature up to 25°C and the total flowrate was as high as 45-50 L/s. It became soon clear that the tunnel, or the water flow from the tunnel, affected the geothermal system. The water level of the reservoir decreased, although production did not increase, and it became more difficult to simulate the water-level with the reservoir model and the chemical composition of the water changed to some extent. To obtain more hot water for the district heating system a new geothermal system in Skarðdalur was explored and in 2010 a new production well was drilled to 700 m with a wellhead temperature of about 74°C. In general, the geothermal water from both systems is very well suited for direct use in house heating and other household appliances. The mineral content is low and scaling has not been a problem. For a long time the water from Skútudalur contained dissolved oxygen, however, which caused corrosion problems for steel pipes. In order to remove the oxygen, the geothermal water was dosed with small quantities of sodium sulfite which reacts with oxygen to form sulphate. The district heating system was owned and operated by the town of Siglufjörður from the beginning until 1991 when RARIK (Iceland State Electricity) bought the system. |