| Title | An analysis of 40 Years of Subsidence Due to Geothermal Production from the Svartsengi-Eldvörp Geothermal System in SW Iceland |
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| Authors | Melissa Anne DE FREITAS, Guðni AXELSSON, Páll EINARSSON |
| Year | 2020 |
| Conference | World Geothermal Congress |
| Keywords | Reykjanes Peninsula, Svartsengi, Eldvörp, TOUGH2, iTOUGH2, subsidence, reservoir model, numerical modelling |
| Abstract | The Svartsengi-Eldvörp geothermal system is a high-temperature system situated within the Reykjanes Peninsula oblique rift in south-west Iceland that bounds the North American and Eurasian tectonic plates. Based on its geological location, Svartsengi is prone to many complex crustal deformation processes. Extensive regional ground subsidence ranging from 7 to 14 mm/year was observed from 1975 to 2015 along the Reykjanes Peninsula, with maximum changes in elevation detected within the main production field at Svartsengi. There have been numerous studies undertaken that have been aimed at identifying and isolating the various signals that contribute to this observed subsidence, with more recent studies proposing a natural subsidence velocity of 6 mm/year along the central volcanic rift of the Reykjanes Peninsula. This paper seeks to contribute to previous deformation studies conducted at Svartsengi through the development of a TOUGH2 numerical model of the Svartsengi geothermal system. The model is calibrated against initial thermodynamic conditions, the average annual mass extraction and reinjection rates during 40 years of production from 1975 to 2015, and the resulting reservoir response. One-dimensional subsidence modelling was performed with the model, using a newly developed subsidence module in iTOUGH2. Modelled results revealed an average subsidence velocity of 3-4 mm/year due to geothermal activity at Svartsengi. Despite only considering one-dimensional subsidence and coupled with the natural subsidence value previously determined, the model accurately represents the total subsidence observed at Svartsengi. This numerical model is therefore capable of predicting subsidence rates due to future geothermal utilization at the Svartsengi and Eldvörp. |