Hydraulic stimulation and

microseismic fracture monitoringwithin

the deep granite holesat the

Soultz-sous-forêts geothermal site

Tischner, T., Schindler, M., Jung, R.

• Introduction

• Hydraulic Stimulation and Productivity Enhancement

• Microseismic Monitoring

• Acidification

• Conclusions

The HDR base moduleHDR/EGS Pilot plantin Soultz

Crystalline rocks at1400 m

1.5 + 4.5 MWe

Geophon Geophon

Production50 kg/s

Production50 kg/s

100 kg/s

600 m 200oC5000mDepth

600 m

1999 : GPK2

GPK2

2000 : Stimulation-GPK2

2003 : Stimulation-GPK3

2004/05: Stimulation-GPK4

Development of the deep reservoir at 5000 m

2002 : GPK3GPK3

2003/04: GPK4

GPK4

2003-2006: Chemical Treatments

0 48 96 144 192 240 288Time (h)

0

50

100

Rat

e l/s

0

50

100

150

200

Diff

eren

tial p

ress

ure

(bar

) at

470

0m (T

VD

)

GPK2; 2000GPK3; 2003GPK4; 2004

Injection volume:GPK2: 23400 m3

GPK3: 34000 m3

GPK4: 9300 m3

0.180.32

0.37

(Productivity in l/s/bar)

Pressure and productivity during stimulation

17-Aug 21-Aug 25-Aug 29-Aug360

380

400

420

440

460

Pre

ssur

e 40

00m

(bar

)

0

10

20

30

40

50

Inje

ctio

n ra

te (l

/s)

PressureData

Rate

Fit

GPK3Aug. 04

Injection tests after stimulation

20-Jan 25-Jan 30-Jan 4-Feb 9-Feb 14-Feb440

460

480

500

520

540P

ress

ure,

470

0m (b

ar)

0

20

40

60

80

100

Rat

e (l/

s)

Rate

Pressure

42 bar

GPK2Jan. 03

Productivity:

GPK2 (4 d): 0.36 l/s/bar

GPK3 (4 d): 0.28 l/s/bar

Productivity (l/s/bar): GPK2 GPK3 GPK4

During Stimulation 0.35(4 d)

0.30(4 d)

0.20(3 d)

After Stimulation 0.35(4 d)

0.30(4 d)

0.20(3 d)

Before Stimulation ≈ 0.02 ≈ 0.2 ≈ 0.01

Comparison of productivities

Productivity during stimulation has been retained after stimulation !

Productivity enhancement can be predicted !

0 1 2 3 4 5Time (d)

0

100

200

Rat

e l/s

0

50

100

150

200

250

Diff

eren

tial p

ress

ure

(bar

)Prediction of productivity enhancement

pressure controlled by rock stress !

Productivity:1. ≈ 0.3 l/s/bar2. ≈ 0.9 l/s/bar

Productivity und hydraulic communication

• Productivity only characterises single wells • Hydraulic communication between the wells is necessary

Microseismic monitoring !

6 seismic observation wells

GPK2GPK2+3

Seismic events (4900-5000m)

GPK2+3+4N

orth

(m)

East (m)

N

SH = 170°; (Röckel, Evans, 2006)

events per 50x50x100m

GPK 4GPK 225° 25°

Microseismic monitoring

Inside into the reservoir development:

• stimulation of planar structures • good hydraulic connection between GPK2 and GPK3• poor connection between GPK3 and GPK4 (boundary ?) • orientation of seismic events along prefered shear directions (N15°E, N145°E)

• control of seismic risk (magnitudes up to 2.9)

Means to reduce seismic risk

• Reservoir development at shallower depth (<= 4000m - Upper Rhine Graben)

• Application of multifracs (lower injection volume - less seismicicty, volumetric stimulation)

22 25 28 03 06 09 12 15 18 21 24 27day in February - March 2005

0

40

80

120

160

wel

l hea

d pr

essu

re (b

ar)

0

20

40

60

80

Inje

ctio

n ra

te (l

/s)

Step rate injection

Step rate injection

Acidizing(0,2 % HCl)

Acidification

GPK4 (2005)

Summary

• Productivity during stimulation = Productivity after stimulation !Productivity enhancement can easily be predicted

• Development of EGS projects under similar conditions as in Soultz (granite..., high shear stress..)

• Multifrac concept/development of shallower reservoir(<4000m)to minimize seismic risk

Outlook Soultz

• Power plant ordered: 1,5 MWel (30 l/s bei 180°C) - Delivery end of 2007

• Additional (hydraulic) stimulation of GPK4 and/or GPK3

Thank you for your attention !