Monday, 30 May
Deep Drilling Project in New Zealand
Last week a Taupo workshop discussed how New Zealand can access its deep and
very hot geothermal resources. These are resources that are about 5 kilometers
below the surface and hold geothermal fluids in excess of 400oC.
“Scientists conservatively estimate that deep geothermal resources in the central
North Island could provide 10,000 megawatts for over 100 years for New Zealand,”
said GNS Science Senior Geothermal Scientist Greg Bignall, a convenor of the
Taupo workshop. The total installed capacity in New Zealand at the present is
9000MWe, about 730MWe of which come from geothermal resources. If deeper resources
can be accessed, they would be able to provide all of New Zealand's electricity
needs with capacity to spare (to be sold to Australia through a future subsea
transmission link? Iceland is contemplating a 1900-km subsea link to sell geothermal
electricity to Scotland. A 2100-km link from North Island to Sydney should be
in the same league).
Greg Bignall had a presentation about this at last year's World Geothermal
Congress in Bali. As noted in that paper, a barrier to the commercial development
of deep geothermal resources is the ability to identify zones of permeability
that could be tapped by deep drilling. It appears that last week's workshop
was another milestone in the Taupo Volcanic Zone - Deep Geothermal Drilling
Project (TVZ-DGDP); a proposal to the International Continental Scientific Drilling
Program (ICDP). The current work is being conducted under the heading of the
Hotter and Deeper Geothermal Program, funded by the New Zealand Foundation for
Research, Science and Technology by a grant of undisclosed amount over three
years covering 2009-2012.
The objectives of the current program are
- Improved understanding of the deep structure and dynamics of the Taupo-Reporoa
Basin; New Zealand’s most intense area of deep-seated geothermal manifestations
(geological and geophysical mapping) and the focus of significant existing
or anticipated proposed geothermal energy development for electricity generation.
- Greater understanding of the physical and chemical nature of the deep fluids
and their flow pathways to be encountered during production (chemistry and
modelling).
At the depths considered, the fluids are expected to be near the critical point
and neither the transport properties nor the interaction with the host rock
are well understood in such regions. While the concept is exciting the challenges
are also enormous as the Icelandic Deep Drilling predict found out. Therefore,
it was appropriate that two people from that project were expected to be at
the New Zealand Workshop last week. I have not been able to attend the Workshop
but I will read the proceedings with interest if they are published.
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