UNKNOWN GEOTHERMAL RESOURCES IN THE AXIAL RIFT ZONE IN ICELANDÓlafur G. Flóvenz, Iceland GeoSurvey – ÍSOR

Presntation at THE 2nd GEORG Geothermal Workshop, Reykjavík, November 14-15th

Geothermal map of Iceland

Bjarnarflag, 5 MW

Krafla, 60 MW

Þeistareykir, 90 MW

Hellisheiði,303 MW

Nesjavellir, 120 MW

Svartsengi, 76 MW

Reykjanes, 100 MW

The volcanic rift-

zone covers

32.000 km2

The geothermal assessment from 1985: Energy above 130°C and 3 km

ICELAND GEOSURVEY

Area Area km2 Accessible Harnessible

Thermal

energy

Thermal

energy

electrical

energy

Power in

50 years

The volcanic zone: TWh TWh TWhe MWe

Known fields 600 160,000 19,400 1,556 3,551

Other active areas 2,150 330,000 46,000 3,667 8,371

Non-active areas 29,250 2,500,000 176,000 10,583 24,163

Total inside

the volcanic zone 32,000 3,000,000 241,400 15,806 36,086

Outside the

volcanic zone 71,000 720,000 57,400 3,100 7,200

Iceland. total 103,000 3,720,000 298,800 18,906 43,286

Status of the exploitation of known Icelandic high-temperature fields

Total potential Harnessed Protected Untapped

Partially harnessed fields 1439 752 170 517

Protected fields 1345 0 1345 0

Likely/possible prodcution sites 462 0 462

Not suitible for production 272 0 272

3518 752 1515 1251Total in MWe

21% of the potential is already harnessed

43% are already or will soon be protected

There is little left to increase the power production

significantly with conventional approach

Utilization category

On hold category

Protected category

Will most likely be protected

Status of the Master Plan for Nature Protection and Energy Utilization

Volcanic rift zone of 32.000 km2

Temperature gradient ≥ 100 °C/km

The Master Plan for Nature Protection and Energy Utilization

Energy utilization category:

➢ Enlargement of existing power plants:

➢Krafla, Bjarnarflag, Þeistareykir

➢ Periphery of already harnessed areas:

➢Hverahlíð, Þverárdalur, Meitill, Stóra-Sandvík, Eldvörp.

➢ New fields:

➢Krísuvík area (Austurengjar, Sveifluháls, Sandfell)

On hold category:

➢ Enlargement of fields in utilization category:

➢ Innstidalur, Trölladyngja.

➢ New fields:

➢Hágöngur, Fremri-námar, Parts of the Torfajökull area, Hveravellir, Hrúthálsar, Öxarfjörður, a few fields where high temperature is uncertain

Protection category:➢ Almost all other known high-temperature

fields are in this category or will almost certainly be.

A new approach is needed for geothermal development for power:

− Drill into the roots of the already harnessed fields into superhot rocks:

− Drill 3-5 km deep wells within the active rift-zone but outside known high temperature fields

These two options are basically different;

➢The first one includes drilling into, or close to, the heat source of the high temperature fields where near magmatic temperatures are expected. The IDDP-project is dedicated to this possibility.

➢The second option calls for conventional but deeper high temperature wells into presently unknown 200-300°C reservoirs:

➢The idea is to look for promising sites for power production in the volcanic rift-zone but outside sensitive areas with respect to nature protection.

➢It requires reliable geophysical exploration and geological mapping of the volcanic rift-zone to identify the most promising places for drilling.

Resistivity and seismic results form the volcanic rift-zone

Figure from Vilhjálmsson and Flóvenz, 2017

Top of the chlorite zone,

temperature > 230°C

Brittle ductile boundary,

temperature likely 500-

600 °C

Zone of low resistivity but

transmits S-waves,

temperature below solidus

of basalts

The axial volcanic rift-zone in Iceland:

− Has most likely average temperature gradient of at least 100°C/km down to 5-6km beneath a 1-2 km thick permeable surface zone.

− By drilling to 3-5 km depth temperature of 250-500°C can be expected.

− By targeting active fault zones considerable permeability is expected.

− Volumetric assessment of stored energy above 130°C down to 3 km within the volcanic rift-zone indicates that it can be used to generate 36 GWe for 50 years.

− The depth range 3-5 km contains at least double the stored heat and the generation capacity – a huge untapped energy resource for the future.

− These conclusions are based on geological observations and geophysical surface exploration within small parts of the volcanic rift-zone. It needs to be confirmed by more detailed exploration and drilling.

Summary I

− Environmental concerns in Iceland and the increased value of tourism to the economy are leading to protection of most of the non-harnessed known high temperature fields in the country that are not already harnessed.

− About 38% of the estimated power potential in the uppermost 3 km of the non-protected, known high temperature fields in Iceland are already harnessed.

− The remaining part is less accessible and might be more difficult to exploit.

− The Icelandic geothermal industry has already harnessed the easiest and most accessible fields.

Summary II

➢A new approach is needed to ensure geothermal energy for power production for the 21st century; deep drilling in existing fields and exploration for unknown fields within the volcanic rift-zone.

➢Both options need considerable R&D effort in the coming years.

➢The need for electricity from renewable resources will obviously increase throughout the 21st century in Iceland.

➢ If we do not perform necessary exploration work and R&D development to harness deep geothermal energy it might lead to unfortunate future decisions with respect to nature protection in order to prevent that shortage of energy hamper our welfare.

Thank you