Geothermal resource find on South Island, New Zealand

(www.thinkgeoenergy.com)

The New Zealand Herald reported on May 18th that University of Otago researchers have made a surprise discovery of a tremendous geothermal resource that could transform the West Coast’s economy. A team of more than 100 scientists from 12 countries, led by Otago University, Victoria University and GNS Science, drilled nearly 900m (3000 ft) into the South Island’s Alpine Fault, with the aim of better understanding how earthquakes occur along geological faults zones.

What they found beneath the ground at the site in Whataroa, north of Franz Josef Glacier, surprised everyone. At 630m (2,050 ft) deep they discovered water hot enough to boil. Such temperatures would typically be found at depths greater than 3km (9,800 ft). Ironically, the finding actually interrupted the researchers’ original aims, as such temperatures were damaging to their scientific equipment. However, it opened up the exciting possibility there was a significant and sustainable energy resource beneath the ground that no one expected to find.

Development West Coast chief operating officer Warren Gilbertson was excited about the find. He stated, ”The discovery could transform the economy and resilience of Westland, and provide a significant and sustainable clean energy resource that could be developed using local people and equipment. The location of geothermal activity and its possible benefit and association to the dairy and tourism sectors provide real opportunities from an economic perspective.” The results of the project, published today in the prestigious international journal Nature, discuss the site’s geothermal gradient, a measure of how fast the temperature increases going deeper beneath the Earth’s surface.

Otago University’s Dr Virginia Toy, one of the lead researchers, said what they found was likely to be unique globally. ”I’m not aware of another fault in the world that has yielded such a high thermal gradient,” Dr Toy said.

The same tectonic forces pushing up the Southern Alps created the extreme temperatures. These forces pushed up hot rocks from 30km (19 miles) deep so quickly that they did not have a chance to cool properly. On top of that, the rain and snow falling on the Southern Alps was flowing deeper into the earth’s crust and then rising closer to the surface, in a siphon effect, bringing the heat with it. She was as surprised as the other scientists by what they had found. Before the drilling, which took place in 2014, she published research estimating temperatures could be as high as 40 C at 1 km (3,900 ft), when what they found was 120 C.

Lead scientist, Victoria University’s Professor Rupert Sutherland said the geothermal conditions discovered were comparable to those in major volcanic centres like Taupo but there were no volcanoes in Westland. Professor Sutherland stated that, ”The geothermal environment is created by a combination of tectonic movement and groundwater flow. Earthquakes fracture the rocks so extensively that water is able to infiltrate deep beneath the mountains and heat becomes concentrated in upwelling geothermal fluids beneath valleys. River gravels that are flushed by abundant West Coast rain and snow dilute this geothermal activity before it reaches the surface.” He emphasized how unexpected the finding was and added, ”Nobody on our team, or any of the scientists who reviewed our plans, predicted that it would be so hot down there. This geothermal activity may sound alarming but it is a wonderful scientific finding that could be commercially very significant for New Zealand.”