| Title | Theistareykir Geothermal Power Plant – Successful Drilling Campaign |
|---|---|
| Authors | Olafur SVERRISSON, Bjarni PALSSON, Asgrimur GUDMUNDSSON, Sveinbjorn HOLMGEIRSSON |
| Year | 2020 |
| Conference | World Geothermal Congress |
| Keywords | Theistareykir, drilling campaign, overpressured areas, well design |
| Abstract | The 90 MWe Theistareykir is the latest geothermal powerplant in Iceland, commissioned in December 2017. The plant is powered by 13 production wells, currently yielding around 110 MWe of steam. The enthalpy of the geothermal resource is in the range of water dominated up to almost dry steam (1200-2700 kJ/kg). The drilling in the most productive part of the field proved to be highly challenging due to overpressure in the upper most 300 m. In the year 2000 municipalities close to the Theistareykir geothermal field formed a special company, Theistareykir Ltd. The main goal was to harness the resource by generating electricity to attract industry into the neighborhood. The first two exploration wells were drilled in 2002 and 2003. In 2005 Landsvirkjun bought a one-third share in the company and funded further exploration drilling and 6 wells were drilled in the years 2006-2009. In 2010 Landsvirkjun bought all shares in the company and took full control over the project. In 2014 a decision was made to build a 90 MWe geothermal power plant at Theistareykir. At that time, total of nine exploration wells had been drilled in the area. Seven of them could provide steam to produce about 57 MWe. Drilling works for 7-10 wells in Theistareykir and Krafla geothermal areas was tendered in 2015 in an open tender. Four international drilling contractors participated and submitted highly competitive bids and a contract was signed with the Iceland Drilling Company, which provided the lowest bid. The drilling campaign started in May 2016 and was completed in August 2017. A total of eight wells were drilled to depth from 2200 m to 2700 m, all of them were deviated. Number of challenges had to be met during the drilling and the first well had to be abandoned after a blowout related to aquifer at 170 m depth. To prevent further failures, the design of the wells in estimated overpressured areas were modified. In continuation all wells were successfully completed. The paper describes the challenges met during the drilling campaign and how they were met to ensure successful results. |