AbstractsBusiness Management & Administration

Tracer testing in the Svartsengi geothermal field in 2015

by Sverrisdóttir 1990 Sigrún




Institution: Reykjavií University
Department:
Year: 2016
Keywords: Orkuverkfræði; Meistaraprófsritgerðir; Jarðhiti; Sustainable energy engineering; Geothermal energy
Posted: 02/05/2017
Record ID: 2130413
Full text PDF: http://hdl.handle.net/1946/23806


Abstract

The Svartsengi geothermal field has been utilized for district heating since 1976 and electricity generation since 1980. Some complications due to the utilization have arisen throughout the years. Those include a rapid pressure drawdown in the field and issues regarding waste water management. The continuous injection of spent geothermal fluid began in 1998 when SV-17 was taken into use. With the addition of SV-24 as an injection well in 2008, the injection rate was slowly increased to 60% of the extraction rate. Pressure measurements showed that the injection provided pressure support to the field, but the addition of a new energy plant and increased production from the field reintroduced the trend of declining field pressure. An important part of geothermal field management is to monitor injection wells and study the ability to increase reinjection. In the summer of 2015 a threefold tracer test was performed in Svartsengi for that purpose. Liquid phase tracers were injected into wells SV-17 and SV-24, 2,7-napthalene disulfonate and 2,6-napthalene disuldonate, and a steam tracer, sulfurhexafluoride, was injected into SV-24. Samples have since been taken from all production wells in the field with the addition of the monitoring well in Eldvörp. At the time of writing the 2,6-NDS has only been detected in well SV-9, while no signs have been noted of 2,7-NDS. However, the steam tracer has been detected in all production wells and sampling for that has been terminated, but no signs were detected in the well in Eldvörp. The tracer returns were modelled quantitatively using a couple of programs from the ICEBOX software package from ÍSOR. TRINV was used to simulate the tracer recovery based on the theory of solute transport and one dimensional flow channel models. TRCOOL was used to predict the cooling in the production wells due to the injection. Only 0.035% of the injected steam phase tracer was recovered in the production wells, indicating a very modest recharge from the injection well to the production wells. Well SV-23 had the largest tracer recovery, but SV-11 experienced the highest tracer concentration. Cooling predictions were calculated for the current injection scenario in well SV-24 and for a scenario where the current injection rate was doubled, for 30 years. For both scenarios the model predicted an insignificant cooling in production wells over the 30 year period. Vinnsla úr jarðhitasvæðinu Svartsengi hófst árið 1976 þegar heitu vatni var hleypt á fyrstu húsin í Grindavík. Fjórum árum síðar hófst raforkuframleiðsla úr svæðinu, þegar orkuver III var tekið í notkun. Með stöðugri framleiðslu hafa nokkur stærri vandmál litið dagsins ljós. Þar á meðal má nefna; hröð þrýstingslækkun vegna vinnslu og losun jarðsjávar á yfirborð. Til að stemma stigu við þessum vandamálum hófst stöðug niðurdæling í holu SV-17 árið 1998. Tíu árum seinna var annarri niðurdælingarholu bætt við, SV-24, og í hægum skrefum var niðurdæling aukin í 60% af upptöku úr svæðinu. Þrýstingsmælingar sýndu að niðurdælingin dró verulega úr hraða…