TAUPO VOLCANIC ZONE DEEP GEOTHERMAL DRILLING PROJECT
Greg Bignall Wairakei Research Centre GNS Science
GNS Science
• 740 MWe installed (~13% NZ electricity generation)
• 29 geothermal areas in TVZ • ~50% with potential for use.
NZ Geothermal Systems
This image cannot currently be displayed.
GNS Science
New Zealand’s Taupo Volcanic Zone (TVZ) is a vast Natural Energy Source
Unproductive
Developed (conventional geo-thermal to 3000 m : 740 MWe developed)
Deep Potential • recent drilling using
large rigs • Resource Temp.
increases with depth • Huge potential for
energy development
Pacific Plate
Taupo Volcanic Zone*
500 m
Aust-Indo Plate
3000 m
* NE-trending, fault-controlled volcano-tectonic depression, infilled by Quaternary volcanic rocks and sediments, in which basement greywacke has been faulted 1-2 km below sea level.
~ 50 km
GNS Science
Limit of shallow
seismicity
The barrier to realising New Zealand’s deep geothermal potential is the ability to identify permeability that can be tapped by drilling.
>400
after Heise et al., (2006)
GNS Science
Integrated Study lead by GNS Science, in collaboration with Victoria Univ. Wellington, Univ. Auckland, Industrial Research Ltd.
FRST Research Programme : (PROJ-20199-GEO-GNS) “Harnessing New Zealand’s Geothermal Resources : Hotter and Deeper”
To assess New Zealand’s deep geothermal resources – providing developers with reduced risk to justify deep exploration drilling :
Science Leader : Dr. Greg Bignall (GNS Science)
Effect of Sea water
Average resistivity of upper 500 m
Project area: Focus for multi-disciplinary research
To image deep geothermal systems in the Taupo-Reporoa Basin To develop predictive models for fluid behaviour, and mechanical rock properties likely to be encountered by deep drilling. 4-year research programme, to end 2012
GNS Science
Preliminary 3-D inversion model results
Effect of Sea water
Average resistivity of upper 500 m
Project area:
• Low resistivity at 0-3 km : interconnected conductive clay minerals within volcaniclastic sediments.
• At 3-10 km, resistive regions overlie low resistivities
in rifted and thinned continental crust.
GNS Science
3-D MT Inversion Model
Rotokawa
Maroa
1000
100
10
1
Models shown to 15 km depth
GNS Science
Effect of hydrothermal mineralogy on (anomalous) MT resistivity data Modelling MT data often identifies zones of anomalous resistivities.
Work undertaken to determine if modelled low resistivities were due to :
• conductive clays
• high permeabilities . (conductive fluids ?)
• change in the systems
• other causes ?
Provides insights into the chemistry / morphology of clay-chlorite, and fluid- rock interactions in geothermal systems.
GNS Science
regional gravity data
Regional survey flown in mid
1990’s, at 760 masl – more recent
airborne surveys undertaken
airborne magnetic data
Re-interpretation / geophysical model of TVZ basement structure
GNS Science
3D Geological Modelling : Leapfrog Geothermal
Tough2 grid generation Stratigraphy
and Structure
GNS Science
OBLIQUE-SLIP
Schematic path along the borehole = 69
/210
3-4
cm w
ide
quar
tz v
ein
Fracture Characterisation
Borehole Logging Imaging
GNS Science
Statically NormalisedCBIL Image
Dynamically NormalisedCBIL Image
Fracture characterisation
• Fracture character (orientation, density, aperture, orientation to local stress field) - to asses contribution to permeability in well feed zones
• Structural controls on permeability in TVZ systems
• Hydrofracturing programme for deep-seated TVZ systems
• Complement tracer studies
McNamara and McLean (2010) Correlation of structurally controlled permeability in geothermal wells using AFIT
GNS Science
New high Temp./Press. apparatus at GNS Science, Wairakei
“real world”
“simulated world”
GNS Science
Three years from now…. we aim for an international science drilling project, to 4-5 km depth, in the Taupo-Reporoa Basin ….
Our current (4-year) programme aims to raise industry confidence to drill deeper, and demonstrate deep-geothermal systems of the TVZ can be developed for their energy potential.
Well drilling could cost $30-40M ?
… requires geoengineering innovation, and ground-breaking science.
Rig 246, MRP: Mokai MK16
GNS Science
Looking forward…. • Current H&D programme (NZ$1M/yr)
runs until the end of 2012. • GNS organised workshops – invited
EGS researchers and companies
• Submit ICDP Pre-Proposal Workshop application in January 2012
• Full proposal to ICDP for science drilling funds. TVZ Drilling in 2013/14
• New Zealand membership to IPGT?
Rig 246, MRP: Mokai MK16
GNS Science
NZ to join elite geothermal partnership
25 May
New Zealand will apply to join the International Partnership for Geothermal Technology (IPGT) says the Minister of Science and Innovation Dr Wayne Mapp. As a member of the IPGT, New Zealand scientists and geothermal industry members will join those from the United States, Australia, Switzerland and Iceland to progress advanced geothermal technologies. “The benefits of membership of this elite grouping are manifold. The IPGT has much to gain from the expertise and capability of New Zealand scientists and industry, and we will benefit from opportunities for geothermal research collaborations and engagement in major international research programmes,” Minister Mapp says. Established in August 2008, the IPGT seeks to develop advanced, cost-effective geothermal energy technologies through international research co-operation. “Geothermal energy is one of New Zealand’s most important renewable energy resources and geothermal electricity generation has grown to 13 percent of total generation in 2010. “As an IPGT partner, New Zealand will be able to strengthen its research programmes designed to realise the true potential of our renewable energy resources.” The Ministry of Science and Innovation will lead the New Zealand government involvement in the initiative. “There is strong support for our application from research organisations and the geothermal industry. I look forward to closer cooperation with the sector on international geothermal linkages”
GNS Science
SCHEMATIC REPRESENTATION OF A DEEP-SEATED GEOTHERMAL SYSTEM
IPGT (“must do”) issues
• Zonal Isolation • Packers • High temperature tools • Stimulation Procedures • Resource Delineation • MEQ fracture targeting & Seismic Risk Assessment • Fracture Characterisation • Artificial Lifting Systems • Pumping Systems • Fluid-rock Interactions • Scaling • CO2 heat transfer • Air cooling technology • O & M costs • Drilling methodoly (e.g. ROP/hydraulic hammers) • Geothermal Database
Whilst US, Iceland and Australia have been at the forefront of EGS initiatives, nations that have developed their conventional resources (c.f. New Zealand)
have much to contribute to the research and technology developments. 17
GNS Science
Some (not all) Questions for TVZ-DGDP 1. What are the physical-chemical conditions, and
fluid-rock interactions n TVZ geothermal systems, below >4km depth?
2. What are the controls on permeability, and
rheology of TVZ geothermal reservoir rocks, at mid-crustal depths? Will the TVZ-DGDP hole intersect the transition from brittle to ductile rheology ?
3. What influences on fracture initiation, propagation and
longevity, that might impact deep well productivity? (at, and below, the brittle to ductile transition?)
4. Will deep drilling confirm our combined geophysical (MT-
seismic), geological and numerical models of the TVZ? How will information change our thinking about the evolution of the TVZ, and development of its hydrothermal systems?
5. What is the potential for sustainable, deep geothermal resource utilisation in the TVZ?
GNS Science
Dr. Greg Bignall GNS Science Wairakei Research Centre 114 Karetoto Road State Highway 1 Private Bag 2000 Taupo NEW ZEALAND http://www.gns.cri.nz
GNS Science welcome collaboration in a variety of geological, chemical and hydrological areas : through Government- and private-funded research, industry-consortia, and academic co-funding.
THANK YOU
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