| Summary: | The Thelamörk low-temperature geothermal system in N-Iceland has for the last nine years been a source of hot water for the Akureyri District Heating Service. The main production well in the Thelamörk field, LÞN-11, was drilled in 1992 intersecting a productive fracture at 450 m depth yielding 17 l/s of 91°C water. Geochemical data indicated deep reservoir temperatures around 100°C and drilling experience in the region shows that the best feed-zones are usually at depths between 1000 to 1500 m. Instead of drilling a new well to hit this target an old 900 m deep well, LÞN-10, was deepened and deviated towards the main fracture-zone of the system. The well intersected a good feed-zone at 1700 m depth with a temperature about 103°C. A five-month production test was performed with careful monitoring of production rates, water level changes and water temperature for well LÞN-10 as well as five other wells in the field. Observed water level changes were simulated with lumped parameter models. The simulation results indicate that the Thelamörk reservoir has a volume of about 1 km3 and an average permeability of 1 Dm. Predicted water level changes during long-term production indicate that the geothermal system will sustain a production between 20 and 21 l/s of 103°C water for the next 8 years, with a draw-down less than 245 m. The deepening of well LÞN-10 has resulted in an increase in the energy production potential of the Thelamörk geothermal system from 4.4 MWt to 6.4 MWt.
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