Ósabotnar Geothermal System, SW Iceland: Low-Temperature Geothermal Exploration and Utilization for District Heating in Árborg
Heimir INGIMARSSON, Helga TULINIUS, Þórólfur H. HAFSTAÐ, Guðni AXELSSON, Sigurður Þór HARALDSSON
[Iceland Geosurvey, Iceland]
The paper presents and describes the exploration and utilization of the Ósabotnar low-temperature system. Following geothermal exploration at Laugabakki in Ölfus, which indicated that the highest heat anomaly was below or east of Ölfusá, the area in Ósabotnar north of Selfoss was studied extensively by drilling exploration wells. Production drilling then began in 2000 when well ÓS-1 was drilled to address the potential decline in energy due to a decline in the output from wells in the Thorleifskot-Laugardælur low-temperature system. Since then, three more production wells have been drilled, wells ÓS-2 in 2007, ÓS-3 in 2013 and ÓS-4 in 2019. The latest well ÓS-4 was completed in January 2019 and is the deepest well in Ósabotnar with a total depth of 2429 m. The well was drilled to meet the growing demand of geothermal water for house heating in Árborg and to explore the geothermal system to greater depth. The drilling was very successful as the well intercepted permeable fractures down to the depth of 2300 m. Temperature profiles in the well indicates that reservoir temperature of 105-110°C can be reached below 1700 m depth. The Ósabotnar reservoir has a temperature of 90-100°C at 1000m depth. Imaging with acoustic televiewer in the well shows that convection of water is mainly in northeasterly striking fractures. Well test analysis indicates that the reservoir has a constant pressure boundary, homogeneous porosity and constant well skin. The permeability in the reservoir is quite large and model calculation indicate that it is possible to increase the production in the area.
|        Topic: Exploration||Paper Number: 11129|