Transcript Slides


One 1 km³ of 200°C hot granite cooled
by 20°C...
...delivers about 10 MW of electric power...
...for a period of 20 years.
www.soultz.net
The estimated EGS potential is huge:
• According to a study presented by the
German Parliament the total technical
potential for electricity production form
EGS sources amounts to about 1’200 EJ
(300’000 TWh),
• which corresponds to 600times the
annual consumption in Germany.
Source: AXPO Holding, Switzerland
A Swiss vision...
50 EGS @ 50 MWe
aus GASVERBUND MITTELLAND AG
There are widely accepted operational numbers,
which are necessary for a technically feasible and
economically viable EGS system (Garnish 2002):
•
•
•
•
•
•
heat exchange surfaces >2.106 m2
in a volume >2.108 m3
production flow-rates of 50-100 l/s
at temperatures 150-200 °C
flow impedance <0.1 MPa/l/s
water losses <10%.
So far, such numbers have not yet been demonstrated;
presently there is no power generation from EGS systems.
Table 1: Goals and achievements in EGS projects world-wide
Project
Time
period
Max.
rocktemp.
[°C]
Los Alamos
(USA)
19731979
232
3500
150-300
~7
<10
2.5
~5
80 -100
Rosemanowes
(UK)
19801993
80
2000
180-270
~15
~25
0.4
~4
200 -300
Hijiori (Japan)
19852003
270
2200
~130
~12
~25
0.3
~7
50 -150
Soultz (F)
19891997
168
3500
~450
~26
0
0.23
~11
~7000
Soultz (F)
(expected….)
1997-
202
5000
600-700 ~100
0
0.12
~50
~20'000
<10 %
0.1
Goals
(Garnish 2002)
150 200
Reservoir
Well
Flow- Water
Flow
Thermal
depth
spacing rate
loss impedance capacity
[m]
[m]
[l/s]
[%]
[MPa/l/s]
[MWth]
50 100
Water
throughflow
[m³]
So there is still quite a bit ahead…
Numerous problems must be solved to reach the
numerical goals and many unknowns need to be
clarified:
irregularities of the temperature field at depth
 favourable stress field conditions
long-term effects, rock-water interaction
 possible short-circuiting
environmental impacts like man-made seismicity
to name only a few.
Temperaturprognose für DHM Basel
T(z) Basel
?
?
T emperat ure (F)
50 100 150 200 250 300 350
0
0
T(z) Soultz
2000
1000
4000Temperature
Rhine
Graben
6000
EP S1
8000
3000
10000
GPK1
12000
4000
14000
GPK2
16000
5000
0
50
100
150
o
T emperat ure ( C)
200
Depth (ft)
Depth (m)
2000
at Soultz/F
profile
230°C
T(z) : Static temperature logs
Well DP 23-1
Desert Peak/NV, USA
T(z)
-1 km
Long-term production
25 MWt
Yield(t) and recovery factor
depend on fracture network
Brown et al. (1999)
Long-term effects
500 l/s
245 MWeyr
Production stop
20 yrs
(Sanyal & Butler 2005)
125 l/s
250 MWeyr
(Sanyal & Butler 2005)
Induced seismicity
•
•
Reinjection is increasingly applied at numerous
geothermal production areas. This changes the pore
pressure conditions and herewith the local stress field.
At The Geysers field/California,USA a large-scale
reinjection of fluids (piped to the field over long distances
from a sewage plant) is underway since a few years. This
creates frequent, perceptible tremors. Induced seismicity
is especially relevant for the EGS technology.
 Monitoring of local seismicity by a suitable seismometer
array (starting well before reinjection/fracturing) is
indispensable.
The key component:
an extended, sufficiently
permeable fracture network
at several km depth, with
suitable heat exchange
surfaces.
Key issue is the creation, characterization and
management of an extended, sufficiently permeable
fracture network at several km depth, with suitable
heat exchange surfaces.
No direct observation/ manipulation is possible to
achieve this;
• it must be accomplished by a kind of remotesensing and –control;
• promising developments to provide the tools
needed here are underway (e.g. the HEX-B and
HEX-S software of GEOWATT).
Remote Sensing and Control in Reservoir Engineering
PTQ(t),
Chem.
?
Reservoir domain:
3D-Code
Cluster
FE/FD Applications for
coupled hydraulicthermal processes
1
2
Wellhead domain:
4
Fracture network
Data range distribution
(spacing, aperture, length)
3
3
Hydraulic boundary conditions
Worst case scenarios
Most probable scnarios
4
Hydraulic tests
Pressure recalculation wellhead
to open hole domain
(density changes!)
Flow/pressure development at
reservoir depth
Production temperatures
Cooling between open hole.and
wellhead
Thermal processes
3D-conductive/advective
High flow-rates
3
2
3
1
HEX-B
pT-Borehole
Simulator
2
Reservoir engineering tool (1): pT- simulator HEX-B
Reservoir properties from wellhead data
GPK2/GPK3 wellheads
Example: European. EGS Project Soultzsous-Forêts, France
Stimulation GPK3, 2003
ca. 10 Tage
Q [l/s]
p(z,t)
tmp(z,t)
Temperature/
HEX-B
pressure profile,
calculated withHEX-B
Flow Exit/Entry
points
Reservoir engineering tool (2): Stimulation Code HEX-S
deterministic
stochastic structures
Coupled hydro-rock mechanical code
Example: EGS Project Coso, USA
GPK4 Stimulation Sep.2004; Modell b1
2.5E+07
2E+07
Wellhead pressure
Pdh [Pa]
IImodl : 6.9-7.4
IImodl : 9.7-10.7
1.5E+07
1E+07
5E+06
0
Stochastische
Strukturen ( S UBI)
0
100000
200000
time [s]
Z
X
Y
-1000
-1500
HEX-S
-2000
x3
Deterministische
Strukturen (UBI)
Pressure distribution
in the reservoir after
24 hours reinjection
with l/s
500
-2500
-3000
500
0 x1
0
x2
-500
-500
ECONOMICS

Various economic models (for example the one at
http://web.mit.edu/hjherzog/www/ developed by the IEA
Geothermal Implementing Agreement) come up with favourable
electricity production prices.

Such models are all based on numerous assumptions, which
have not yet been substantiated.

So far there is no practical experience with real costs.

In any case, substantial front-up investment is needed since
EGS technical feasibility at a given site can be demonstrated by
deep drilling and circulation only.

Co-generation (and selling the heat) could secure a better price
than electricity generation alone.
There are great challenges but still numerous problems ahead.
 The real challenge is to work for problem solutions, through a wide
spectrum of disciplines: earth sciences, physics, chemistry,
engineering, economics….
 What will really be needed is the planning and establishment of
successful EGS systems in several, contrasting geological settings;
 Key issue will be remote sensing and –control in creating,
characterizing and operating the fracture system at depth;
 Joining forces by a broad, internationally based interdisciplinary
effort like ENGINE is an important step towards the ambitious
goals;
 The EGS adventure resembles an Alpine tour: the difficulties and
struggles underway are numerous and major, the prospect
however (“the view from the top”) is rewarding.
Many thanks for your attention !
Prof. Dr. L. Rybach
GEOWATT AG Zurich
Dohlenweg 28
CH-8093 Zurich, Switzerland
[email protected]