unknown geothermal resources in the axial rift zone …€¦ · unknown geothermal resources in the...
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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