Perspectives for the sustainable use of geothermal resources

1. Perspectives for the sustainable use of
geothermal resources
Maren Brehme

2. 2
1
2
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4
5
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8
9
10
10 20 30
20
15
10
5
0
Well number
MWe
Drilling history of a geothermal field
2

3. 3
1
2
3
4
5
6
7
8
9
10
23
28
11
1213
14
15
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171819
1920
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24
25
29
30
Well number
Drilling history of a geothermal field
3
20
15
10
5
10 20 30
0
MWe

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4
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23
28
11
1213
14
15
16
171819
1920
21
22
24
25
29
30
Well number
Drilling history of a geothermal field
4
World
Well capacity MWe
Numberofwells
(ICF-report, 2015)
20
15
10
5
10 20 30
0
MWe

5. 5
Where to drill the next well?

6. Structural-geological conceptual model
6
 Complex structural-geological setting
 Two phases of faulting
(Brehme et al., 2014)
Where to drill the next well?

7. Hydrochemical conceptual model
7
 Separation of different water types by faults
(Brehme et al., 2014)
Where to drill the next well?

8. Discharge measurements in rivers
12 L/s
5 L/s 44 L/s
39 L/s
76 L/s
64 L/s
8
 Infiltration of river water into faults
 Measured permeability: 2*e-15 – 2*e-14 m2
(Brehme et al., 2014)
Where to drill the next well?

9. 9
A new exploration tool
 A blank area on the map
Where to drill the next well?

10. A new exploration tool
10
-30m -15m 0m
Depth color scale
G01
C11
10 m10 m
12 m
14 m
12 m
8 m
6m
12
m
4m
2m
14 m
493
996.5
2.97
C11
0
5
10
15
20
25
30
35
27.4
G01
484 486
996.4 996.7
2.77 2.81
27.5 27.9
0
5
10
15
20
25
30
35
Temperature [°C]Water inflow
 Tectonic structures in
lake
 Inflow of hot, saline,
acidic water
pH
Density
Conductivity
Temperature
Where to drill the next well?
(Brehme et al.,
Nature Scientific Reports, 2019)
0
-30
-15
140700
140200
703000
703400
0
-30
-15
703400
140200
A B
10m 20m

11. Impact of results on the current exploitation strategy
11
afterbefore
20
15
10
5
10 20 30
0
Well number
MWe
20
15
10
5
10 20 30 40
0
Well number
MWe
Drilling efficiency
~40%
Drilling efficiency
~55%
Where to drill the next well?

12. 12
How to operate sustainably?

13. Declining injection and stimulation treatments
13
(Brehme et al., 2018)
How to operate sustainably?
• Acidization HCl+HF
• Mechanical cleaning
• New side track
• Radial jet drilling

14. Mineral precipitation: A reason for injectivity decline
14
After 1 year in
the lab
After 2 years of operation
in the pipes
• Ca-Mg: Dolomite
• HCO3-Ca: Calcite
• HCO3-Ba: Witherite
(Brehmeetal.,2018)
Precipitation
InhibitorBiofilm
Acidation
Fines migrationCorrosion
high reverse correlation high correlation
How to operate sustainably?

15. Improper well completion: A reason for injectivity decline
15
Filter residual
after 6 weeks
of operation
circulation behind liner
clay mobilisation
clay input to the reservoir
Quantity%
0
8
4µ
60µ
0.25µ
after filter
1µ
Filter
(GTN, 2017)
Precipitation
InhibitorBiofilm
Acidation
Fines migrationCorrosion
Quantity%
0
8
0.25µ
1µ
4µbefore filter
Filter
How to operate sustainably?

16. Precipitation
InhibitorBiofilm
Acidation
Fines migrationCorrosion
Biofilm and Corrosion: Reasons for injectivity decline
16
Magnetic filter residualOrganic filter
residual
Check of casing and pipe integrity
Name DOC mg C/l
Production <1.6
Injection
before filter
<1.9
Injection
after filter
<2.0
Injection
before filter
<2.2
Injection
after filter
<2.4
How to operate sustainably?

17. 75 cm 75 cm
relativepermeability
relativepermeability
2003 2016 2003 2016
year year
30
20
10
0
30
20
10
0
m3/h/bar
m3/h/bar
17
Near wellbore flow occlusion
(Brehme et al., 2018)
 Shallow penetration of
occlusion
 Stimulation has to
concentrate on near
wellbore area
How to operate sustainably?

18. 75 cm 75 cm
relativepermeability
relativepermeability
2003 2016 2003 2016
year year
30
20
10
0
30
20
10
0
m3/h/bar
m3/h/bar
18
Near wellbore flow occlusion
(Brehme et al., 2018)
 Shallow penetration of
occlusion
 Stimulation has to
concentrate on near
wellbore area
How to operate sustainably?

19. 19
Hazard preventive studies
Sample 1
mg/L Fe pH
10 6.32
10-25 5.71 + HCl
Sample 2
mg/L Fe pH
10 6.37
3-10 7.05 + O2
precipitation basin
Trias Westland Injection
Should we use a precipitation basin?
 Research on possible risks before operation
 Suggestions for propper fluid handling
Experiment 1
Experiment 2
How to operate sustainably?
Sample + HCl
Sample + Time + O2
1
2

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