drilling, stimulation and reservoir assessment for egs and ugr projects thomas kohl, geowatt ag...
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Drilling, stimulation and reservoir assessment for EGS and UGR projects
Thomas Kohl, GEOWATT AG
Sverrir Thorhallsson, ISOR
European EGS/UGR Projects
• Several European research projects in past 30 years • Widely different geological conditions • New projects in construction
Two ENGINE workshops "Best Practices" are planned• Economic development of resources
improving output of wells by stimulation / drilling lowering the cost of drilling.
• Reservoir assessment and available geoscientific information.
• Recent technological advances in these areas will be examined
Countries with conv. production (large/small)Failed / abandoned EGS/UGR projectsRunning EGS/UGR projectsPlanned EGS/UGR projects
Development from HDR to EGS Concept
Typical System Requirements:
Example: Production of 35 MWth (3.5 MWel) over 30 yr duration: Heat exchange area ~1.7 km2
Maximum temperature decrease after 30 yr: 20% Flowrate 45 l/s Flow impedance 0.2 GPa per m3/s
Rosemanowes Fenton Hill Soultz
Soultz EGS System
Northern Upper Rhine Graben Temperature distribution in 500m
EPS1
GPK1
GPK2
Temperature distribution in Rhine Graben
GGA, Hannover
Improve output of wells
How to improve the yield of wells?• Larger diameter wells• Underbalanced drilling• Well stimulation• Use of water only for drilling• Deep pumps
DrillingNew Equipment
Effectiveness in Drilling
Jarðboranir hf.
Top Drive and Automatic Pipe handling
Jarðboranir hf.
Modern Geothermal Rig
Stimulation Techniques
Chemical stimulation• Corrosion• Effect of concentration
Mechanical (hydraulic) Stimulation• Proppant vs water frac• Predicability• Optimizing test duriation
Stimulation by Explosives
Thermal Stimulation
Workshop "Stimulation of Reservoir and Induced Microseismicity"
29. June – 30. June 2006
Kartause Ittingen, Warth, Switzerland
1. July 2006: Excursion "Grimsel Test Site"
Registration deadline: 25. March 2006flyers (draft) available
Chemical stimulation
Acidization is used for • removal of skin damage from drilling operations• increase of formation permeability in undamaged wells.
The injection of acids is performed • at modest flow rate (below pressures for mechanical stimul
ation)1) preflush, usually with hydrochloric acid2) mainflush usually with a hydrochloric – hydrofluoric acid mix
ture. 3) postflush/overflush usually with soft HCl acid solutions or wi
th KCl, NH4Cl solutions and freshwater.
Improvement of the well conditions can be generally observed (largely varying success).
André & Vuataz
Mechanical (hydraulic) Stimulation
Faulting (shear fracturing)• Increase of pore pressure• Slip of pre-existing mechanical discontinuities• Generation of larger apertures / or new faults
Mohr-Coulomb Criterion
Microseismicity• Prediction of Magnitudes (Gutenberg-Richter)• Identification of large structures (e.g. multiplet analysis)• Identification of hydraulic diffusivity
Stimulation of multiple fracture sets, mostly in crystalline rock
nc tan
h
H
Evans
Mechanical (hydraulic) Stimulation
Jointing (tensile fracture)• Develops perpendicular to least principal stress
Criterion
Applied mostly in sedimentary rocks
Creation of single, far extending fractures
pf
f
PSP
SP
min
min
Stimulation of GPK4 (Sep04): Microseismic Development
E.E.I.G.
Top South West
Located seismic events
Calculated Shearing Events
Critère de rupture [MPa] :
Modeling TechniquesFRACAS
C. Baujard/ D. Bruel
Modeling TechniquesHEX-S: Prognosis of stimulation
Forecast Measurement
C. Baujard
-5500
-5000
-4500
De
pth
0
500
-2000-1500-1000
Northing
XY
Z
-6000
-5000
-4000
-3000
-2000
x3
-100001000
x1-2000-100001000
x2
XY
Z
stim0047.datstim0048.datstim0049.datstim0050.datstim0051.datstim0052.datstim0053.datstim0054.datstim0055.datstim0056.datstim0057.datstim0058.datstim0059.datstim0060.datstim0061.datstim0062.datstim0063.dat
time [s]
Pd
h[M
Pa
]
Qin
Om
eg
a
100000 200000 3000000
5
10
15
20
0
10
20
30
40
50
60
70
80
90
100
Ref.pressure45.0 MPa
time [s]
Pdh
[Pa]
Flo
wra
te[l/
s]
0 100000 200000 3000000
5E+06
1E+07
1.5E+07
2E+07
2.5E+07
0
10
20
30
40
50
60
70
80
90
100
Pdh B1
Qinj [l/s]
Pdh C2
Pdh C3
GPK4 Stimulation Sep.2004; Modell b1/cx
IImodl : 6.9-7.4 IImodl : 9.7-10.7
Conclusion
Drilling, stimulation and reservoir assessment are most important for EGS and UGR concepts
Underbalanced drilling may help to maintain natural permeability
Experience exists on• EGS in Europe• on stimulation techniques
Hydraulic post-stimulation behaviour has not always improved
The complex interplay between microseismicity and fluid pathways can be forecasted