GEORG Geothermal Workshop 2016 SESSION B2, Midstream

1. Geothermal Engineering Integrating Mitigation of
Induced SEismicity in Reservoirs
Kristján Ágústsson
Ólafur Flóvenz, Egill Á. Guðnason

2. The GEISER project started at the beginning of the year 2010. It was funded by the
European Commission. ÍSOR’s participation was supported by GEORG. The specific
objectives of GEISER were:
to understand why seismicity is induced in some cases but not in others
to assess the probability of seismic hazards depending on geological setting
and geographical location
to propose licensing and monitoring guidelines for local authorities,
including a definition of acceptable ground motion levels
to investigate strategies for ‘soft stimulation’ that sufficiently improve the
geothermal reservoir’s hydraulic properties without producing earthquakes that
could be felt or cause damage

3. Guidelines – best practice
• IEA – GIA (International Energy Agency –
Geothermal Implementing Agreement)
• IPGT (International Partnership for Geothermal
Technology)
• Department of energy, USA
• and more

4. To address these objectives,
four main topics were identified:
• Analysis of induced seismicity
• Understanding the geomechanics and processes
• Consequences of induced seismicity - hazard, risk
• Strategies for the mitigation of induced seismicity

5. WP1: Project Management. GFZ.
WP2: Compilation of induced seismicity data and literature from geothermal sites and
selection of sites for detailed study. ISOR.
WP3: Analysis of Induced Seismicity. GFZ.
WP4: Understanding the Geomechanical Causes and Processes of Induced Seismicity. BRGM.
WP5: Seismic Hazard Assessment. ETHZ.
WP6: Strategies for EGS operations with respect to Induced Seismicity (Mitigation). TNO.
WP7: Dissemination. BRGM.

6. Icelandic interests
• To study seismicity in Icelandic geothermal systems,
particularly induced seismicity
• Geiser: to propose licensing and monitoring guidelines
for local authorities
– These guidelines could become a recommendation from the
Europian Commission
– It was considered important that Iceland would take care of its
special interests in this respect due to different circumstances in
utilisation compared to EGS
• At the time of the start of GEISER induced seismicity
was not considered an issue in Iceland

7. Special Icelandic cicumstances
• Geothermal utilization in Iceland is until now from natural geothermal
reservoirs
– GEISER focused on enhanced geothermal systems – EGS-systems
• Geothermal fields in Iceland are in tectonically active areas and the
permeability is mostly fissure and fracture permeability formed in
earthquakes
• It was assumed that possible induced activity would not change the
character of the natural seismic release significantly

8. Examples of induced seismicity
• Gráuhnjúkar, Hengill, SW Iceland
• Húsmúli, Hengill, SW Iceland
• IDDP-1, Krafla, N Iceland

9. The first quakes occurred close to
the bottom of the well.
Then they migrated laterally away
from it, probably along the top of
the molten zone.
Finally the activity was mostly
along an inclined plane.
Earthquakes during
injection into the bottom
feed zone of the IDDP-1
well, Krafla.

10. HE-8
HE-
10
HE-12/15HE-5
HE-7 HE-
57
HE-16HE-13 HE-29
HE-19
HE-35
HE-30
HE-
41/43/45/47
HE-40 HE-52HE-
42/44/46
HN-4
HN-3
HN-2 HN-6
HN-5/7
HN-
10
HN
-8
HN-17
HN-12
HN-11HN-9 HN-15
HN-14
HN-13
HN-16
Data from the Icelandic
Meteorological Office

11. Remarks / Iceland
• Wellhead pressure is low and the earthquakes are
triggered by increased pressure or caused by
thermoelastic process
• In high temperature areas which are located in volcanic
centres the events are small indicating weak crust
• Areas in and around shear zones of the plate boundaries
are able to produce large events but the activity
decreases rapidly with continued injection (Húsmúli)

12. Húsmúli – change of attitude
• A full-scale injection at Húsmúli in Sept 2011 with a
rate of more than 500 L/s caused seismicity that was
felt in neighboring communities and it changed the
general public attitude

13. Results - recommendations
• Reykjavík Energy, that operated the field put together
a group of specialists, including participants from
GEISER. It analyzed the process and recommended
the best practices based on the work in the GEISER
project
• These recommendations were used by the National
Energy Authority, in cooperation with the power
companies, to compile regulations and
recomendations for reseach- and operation permits for
geothermal power plants in Iceland.

14. Other benefits of GEISER for
Iceland
• General knowledge was gained about
induced seismic activity
• New methods and monitoring
• Warning systems (traffic light), e.g. now in
use during drilling of the IDDP-2 well
(DEEPEGS)

15. Thank you