THE SOULTZ EGS PROJECT AND ITS SOCIAL ENVIRONMENT: HOW TO REDUCE THE RISK OF PUBLIC OPPOSITION

THE SOULTZ EGS PROJECT AND ITS SOCIAL ENVIRONMENT:

HOW TO REDUCE THE RISK OF PUBLIC OPPOSITION

Nicolas CUENOT & Daniel FRITSCH

GEIE “Exploitation Minière de la Chaleur” / EEIG “Heat Mining”

Route de Soultz – BP 38 – 67250 Kutzenhausen – France

Tel.: +33 3 88 80 53 63 / Fax : +33 3 88 80 53 51 / www.soultz.net

Corresponding author: [email protected]

OUTLINE:

Hydraulic stimulations and induced seismicity

Consequences for public acceptance

Scientific research on larger magnitude events

Scientific cooperation

Use of other stimulation techniques

Communication

Hydraulic stimulation and induced seismicity

4 massive hydraulic stimulation experiments

Injected volume

Maximum flow rateMaximum overpressure

Induced seismicity

Larger magnitude events

GPK2 (2000) ~23400 m3 50 l/s 13 MPa~14000

(located)

75 (M≥1.8)

1 x 2.6

2 x 2.4

GPK3 (2003) ~34000 m3 50 l/s; 60 & 90 l/s “Focused stimulation”

18 MPa~22000 (located)

43 (M≥1.8)

1 x 2.9

2 x 2.7

GPK4 (2004) ~9300 m3 45 l/s 17 MPa~5800

(located)

3 (M≥1.8)

1 x 2.0

GPK4 (2005) ~12300 m3 45 l/s 19 MPa~3000

(located)

17 (M≥1.8)

1 x 2.6

1 x 2.3

Hydraulic stimulation and induced seismicity

Consequences for public acceptance growing fear due to:

• the largest earthquakes (vibration, sound, moving objects)

• repetition of felt earthquakes (within a short period and from one stimulation test to another)

lots of phone calls (complain or ask for information)

complaints to local authorities from individuals or associations

articles in local newspapers

around 30 complaints for presumed damages, which were evaluated by experts from insurance companies

long-term risk of strong opposition to the project

Scientific research

First action → scientific research to understand the occurrence of the stronger earthquakes:

presence of large faults, able to produce seismic events of such magnitudes

high stress drop: strong energy release on small fractures

From Dorbath et al., 2007

Scientific research

Other actions:

Installation by EOST of a permanent surface seismological network before the stimulation of GPK3

Installation of surface accelerometers at different places in Soultz to monitor the effective ground acceleration

From Dorbath et al., 2007

Scientific research

International cooperation

creation of an independent experts group, which is in charge to evaluate the stimulations programs in terms of seismic risk

participation to different workshops on induced seismicity

creation of an EHDRA workgroup “Seismo-hydraulics”: 4 meetings were organized to discuss issues related to stimulation processes

Organization of a yearly EHDRA Scientific Meeting, with at least one session dedicated to microseismicity

Technical measures

In order to limit the induced earthquakes in terms of number and magnitude, we try to act on the medium by performing chemical stimulations instead of pure hydraulic stimulations, as we know that the fractures are sealed by hydrothermal deposits (calcite, silica and clays)

a one-year program was built with the help of geochemists and companies, which have experience in chemical stimulation

GPK4 was the target, as this well exhibited a low productivity index after the 6-months circulation test

RMA (Regular Mud Acid) in May 2006; max flow rate: 28 l/s, aiming at dissolving minerals like clay, feldspars and mica.

Chelatants (NTA) in October 2006; max flow rate: 40 l/s, aiming at acting on calcite

OCA (Organic Clay Acid) in February 2007; max flow rate: 55 l/s, used in high temperature medium with high clay content.

Technical measures

Results of the chemical stimulation program:

Improvement of the productivity of the well

lower volume of injected fluids; Lower flow rates, except for short periods (“flush”) → lower overpressures

RMA: ~20 seismic events, highest magnitude: 1.9, but the earthquake was not felt.

NTA: no seismicity

OCA: ~80 seismic events, highest magnitude: 1.5

direct consequence: NO complaint from the population and a more peaceful environment around the project

Upper figure: seismicity during the RMA test

Lower figure: seismicity during the OCA test

both from EOST (J. Charléty & L. Dorbath)

Communication Before any stimulation test, a information letter is sent to the population to present the stimulation program and the possibility of induced seismicity

Following the strongest event, public information meetings were organized by the EEIG with the participation of seismologists to explain the stimulation tests and to give more precise information about induced seismicity and, to a larger extent, seismology

A small macroseismic investigation was achieved after the M=2.9 earthquake to get information about how people felt the vibrations

Accelerometers were installed in the Police buildings and in the cellar of one inhabitant’s house to record the effective ground acceleration (presumed site effect)

Communication Organization of a public information meeting every 2 months to present the project

• 40 to 50 people at each meeting, mainly students and local population

• numerous questions about the project, and mainly about earthquakes

• people looks very interested and satisfied after the meetings

Organization of special information meetings for associations, groups of students, companies…

Publication of a regular 2-folds newspaper, which is written in 3 languages and distributed to a large audience to present the development of the project and the main events.

The Web site is regularly updated.

Conclusions

Working on three different ways contributed to significantly increase the social acceptability by producing a more quiet environment around the project for 2 years now:

• Scientific → better understanding of induced seismicity

• Technical → use of low seismicity-inducing stimulation techniques

• Communication → better information to a motivated population

The population and local authorities now fully supports the project, since they noticed that we are doing our best to avoid the possible nuisances, or at least, to inform them honestly about them

For the future, once people will see the concrete achievement of our project (and others), they will be able to make a better balance between the benefits given by geothermal projects and the possible disturbances related to their development.