ÍSOR was the main geological consultant appointed to oversee the drilling of a new well, LH-4, for Skagafjördur District Heating Company. Expectations were exceeded, as both the volume of water was greater and the temperature higher than expected. The aim was to reach 4 L/s and water temperatures of up to 100°C. However, drilling resulted in a volume of more than 30 L/s and temperatures of up to 110°C. It is unusual to encounter water of such temperatures from shallow wells in the low temperature geothermal areas of Iceland. Skagafjördur District Heating Company intends to use the water for the domestic heating of Fljót.
Geothermal Potential of the Area
Geothermal waters are fairly widespread on Tröllaskagi in north Iceland and district heating is present in all villages, most recently in Hofsós. The water for Hofsós comes from Hrolllaugsdalur, and was found after extensive exploration. Over recent decades, Skagafjördur District Heating Company has also laid pipelines to more rural areas of the province, thus providing geothermal heating almost universally.
Geothermal water in Fljót has long been known to exist in several places and was explored to some extent in the eighties. Hot water had already been used on some farms in the area, especially near Reykjarhóll in East Fljót and at Bárdarlaug and Sólgardur where there is a school and a swimming pool.
Exploration and Drilling Operations
Extensive surface exploration was conducted in the area before 1990, and it became evident that the heat followed generally north-south striking faults. Geochemical analyses indicated that the water was hotter in the western part of the region in comparison with the eastern part. Resistivity measurements indicated the same. Drilling for hot water was conducted both in Lambanesreykir/Hraun and at Reykjahóll in Bakkar in the eighties for fish farming. However, eventually the farms were abandoned in spite of the hot water supply.
In the farmland of Langhús, geothermal water from Dælislaug Spring was exploited but following problems with the utilization, a well was drilled nearby in 1997. During the operation a fault was penetrated at 80 m depth, feeding boiling water into the well. Another well was sited according to new geological research and drilled to 200 m depth in 2014, thus producing enough water for Skagafjördur District Heating Company to begin the construction of a pipeline for the Fljót area in 2015. However, the volume of water was not sufficient for the whole area and a new well was drilled, but failed to produce any hot water. It became evident that the fault dipped contrary to predicted models. The fourth hole (LH-4) was designed according to revised structural mapping and drilled in 2015-2016. When drilling reached 170 m, a significant volume of 30 L/s of hot water was erupting from the hole.
It is of interest that so much water was retrieved from such shallow depths. Consequently, with respect to temperatures of 110°C, relatively shallow exploitation wells requiring pump shafts should be designed for further drilling.
From the results of these drilling operations it can be concluded that there is plentiful artesian water in the Fljót area.