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Breathing new life into the iconic Wairakei geothermal resource

Wairakei geothermal facilities, Taupo/ New Zealand (source: Contact Energy)
Alexander Richter Alexander Richter 15 Apr 2015

In 2014 Contact completed a four year investment programme designed to prolong the life of the power station, introduce additional operational flexibility in the use of the Wairakei geothermal resource while lowering costs.

Contact Energy’s pioneering Wairakei geothermal power station in New Zealand was developed in 1958 – the second significant geothermal power station in the world and the first to utilise wells that produce a mixture of steam and water. 57 years later it continues to operate with availability performance that owners of a new station would be proud of (96% in 2014). In 2014 Contact completed a four year investment programme designed to prolong the life of the power station, introduce additional operational flexibility in the use of the Wairakei geothermal resource and lower the cost of generation. We caught up with Mike Dunstall, GM Geothermal Resources and Development from Contact ahead of the World Geothermal Congress in Melbourne to find out more about the journey.

What investments has Contact made to prolong the life of the Wair?kei power station and better utilise the resource?

“We recently completed a major programme of work to upgrade our Wair?kei assets. Our newest power station Te Mihi, commissioned in May 2014, was part of this project. We also developed new steamfield connections, drilled a number of new wells, expanded the steamfield and invested in the Wair?kei bioreactor.  Together, these changes aim to prolong the life of the Wair?kei power station and better utilise the steamfield resource.”

How did the changes improve the environmental performance of the 57 year old station?

“One of the major objectives was to reduce our impact on the Waikato River.  By increasing reinjection and developing the Wair?kei bioreactor we were able to greatly improve the environmental performance of the plant. The bioreactor uses naturally occurring bacteria inside a 378km pipe field to remove hydrogen sulphide (H2S) present in the station’s cooling water before returning it to the Waikato River. This is the first bioreactor in the world to be used in geothermal electricity production.  Locating the new plant high up on the hills at Te Mihi also helped with air dispersion and cooling tower performance”

How has the addition of Te Mihi benefited Contact’s operation and what unique challenges were involved in its development?

“Te Mihi provides greater flexibility in the way we use our permitted daily take of geothermal fluid, which enables us to run our stations to better meet energy trading requirements. It enables us to undertake planned maintenance without significantly disrupting output. Crucially, it’s also provided a range of strategic options for the future. Due to the close positioning to the geothermal resource and use of the latest steam turbine technology Te Mihi is 15-20% more efficient in its use of steam than the Wairakei power station.”

“The build was a significant and complex challenge with over 3.1million hours worked and up to 600 people on site during the peak of construction. One of the unique aspects of Te Mihi was the need to build and integrate the new power station into a live steamfield environment that has been supporting the Wair?kei plant since 1958, and to do this with minimal disruption during construction.”

What new innovations have been developed along the way?

“Innovation has really been a natural part of the process of our development. From the way we used geophones to develop a seismic network through to developing new ways of analysing reservoir parameters, through to using new techniques in well drilling and maintenance, such as ‘broaching’ and using coil tubing in well workovers. We have successfully applied new innovations and approaches in our work, and it has resulted in some great efficiencies.  The bioreactor is also another great example of innovation in action”

Learn more at the World Geothermal Congress

Contact is a sponsor of the 2015 World Geothermal Congress in Melbourne during 20-24 April. Members of the Contact Energy team will be presenting a range of technical papers at the event, including a session on the Te Mihi Steamfield Production Design, Broaching and the seismic monitoring of the Wairakei Field. Contact will also be represented in the New Zealand Trade and Enterprise exhibit stand in the foyer of the congress.

More information on these three presentations can be found by following these links:

About Contact:

Contact Energy is one of New Zealand’s largest electricity generators and retailers and owns and operates 12 power stations, including five geothermal power stations which have a combined gross installed geothermal capacity of 431 megawatts.

Source: Contact Energy