MSc defence by Melissa de Freitas

Melissa de Freitas, MSc Fellow in geophysics at University of Iceland will give a presentation on her MSc project on Wednesday 5 September, 2018 at 16:00 at University of Iceland, Askja building, meeting room on 3rd floor (Fundarherbergi Jarðvísindastofnunar 3. hæð).

The title of the project is:

Numerical Modelling of Geothermal Reservoirs, with subsidence as an added calibration parameter: Case Study of the Svartsengi Geothermal System, SW Iceland

Melissa's supervisor:

Dr. Guðni Axelsson, Director Geothermal Training, ISOR
Dr. Páll Einarsson, Professor emeritus at the Faculty of Earth Sciences, University of Iceland

The external examiner will be Dr. Lárus Þorvaldsson geothermal reservoir engineer, Vatnaskil Consulting Engineers.

Everyone's welcome to attend.

Abstract

The Svartsengi-Eldvörp geothermal system is a high-temperature system situated within the Reykjanes Peninsula oblique rift in south-west Iceland, a part of the boundary between the North America and Eurasia plates. Extensive regional ground subsidence ranging from 7 to 14 mm/year has been observed from 1975 to 2015, with the maximum changes in elevation detected in the production field at Svartsengi. Numerous studies done throughout the years have sought to identify and isolate the various signals that contribute to the observed subsidence. Recently, the combined analysis of a variety of geodetic studies has proposed a natural subsidence velocity of 6 mm/year along the central volcanic rift within the Reykjanes Peninsula. This project however, seeks to contribute to the existing deformation studies at Svartsengi by setting up a TOUGH2 numerical model of the Svartsengi geothermal system, calibrated against the average annual mass extraction and reinjection rates from 1975 to 2015. One-dimensional subsidence modelling was performed with the model, using a newly developed subsidence module in iTOUGH2. The model reveals that high permeabilities, pressure drawdown and changes in the rates of production and reinjection have been major factors that have influenced the contribution of geothermal production to the total observed vertical deformation at Svartsengi. Modelled results indicate an average subsidence velocity of 3-4 mm/year as a result of mass extraction due to geothermal activity. Coupled with the natural subsidence value previously determined, this value is capable of accurately representing the total subsidence observed at Svartsengi. The numerical model is therefore a valuable tool for predicting subsidence rates due to future production at Svartsengi and Eldvörp.