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)

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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

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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.

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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

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3D Geological Modelling : Leapfrog Geothermal

Tough2 grid generation Stratigraphy

and Structure

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OBLIQUE-SLIP

Schematic path along the borehole = 69

/210

3-4

cm w

ide

quar

tz v

ein

Fracture Characterisation

Borehole Logging Imaging

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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

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New high Temp./Press. apparatus at GNS Science, Wairakei

“real world”

“simulated world”

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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

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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