| Title | Sustainable Development of the Seltjarnarnes Geothermal Field, Iceland, Through Exploration Drilling and Reservoir Modelling |
|---|---|
| Authors | Hrefna KRISTMANNSDÓTTIR, Eric MYER, Sveinn Ó. PÃLMARSSON, Axel BJÖRNSSON, Egill M. ÞORBERGSSON, Smári GUÃFINNSSON |
| Year | 2020 |
| Conference | World Geothermal Congress |
| Keywords | Sustainable development, exploration wells, three-dimensional reservoir model, electricity production |
| Abstract | The Seltjarnarnes geothermal field was first harnessed about 50 years ago and has been utilized for a local heating system since 1972. The field is located on a peninsula within the town of Seltjarnarnes, a suburb of Iceland’s capital city ReykjavÃk. About 50 L/s of 95-120 °C hot water is produced from three main feed zones using four production wells. About 40 % of the return water is collected and mixed with the produced water to maintain an optimal temperature for distribution. As the area around the wellfield is densely inhabitated and in close proximity to the coast, conventional reservoir exploration methods are limited. Drilling of shallow exploration wells is therefore the best method to map the geothermal field and nine such wells have been drilled to date. In the last five years, four wells have been drilled providing valuable information on the properties of the geothermal reservoir and on locating possible new production wells. The first three-dimensional reservoir model of the system was constructed in 2002 and was updated in 2016 using the available up-to-date production data. The updated model was used to forecast the reservoir response to several future production scenarios. The results show that a production increase of 10 L/s is sustainable for the next 20 years using the current production wells with unaltered pump depths. It should be possible to increase current production by 20 % through use of the existing production wells, and even further by lowering the production pumps in some wells. The model can be used to calculate additional scenarios with increased production from the reservoir. Evaluation of the feasibility of small scale electricity production is ongoing and preliminary results show that the district heating will benefit from the ORC system with better control of the fluid temperature and lowering or eliminating the electricity bill. As the geothermal field is far from being fully exploited, the possibilities for further sustainable utilization are manifold. |