a1 future production from the seltjarnarnes geothermal field hrefna kristmannsdóttir
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Future production from the Seltjarnarnes geothermal field
Hrefna Kristmannsdóttir, Axel Björnsson, Eric Myer, Sveinn Óli Pálmarsson, GísliHermannsson
#GGW2016
The Seltjarnarnes geothermal field is a boiling low-temperature
geothermal field located within the town, Seltjarnarnes
Reservoir temperature exceeds 150 °C
Supposed main upflow
The geothermal field has been
developed for a local heating system
during the last 45 years. In the town
Seltjarnarnes, a suburb of the capital
city, there are about 4300 inhabitants.
Rannsóknasvið
The geothermal field is located in
the same Quaternary rock
formation within the Kjalarnes
caldera as the five other
geothermal fields within the
Reykjavík, capital city region.
Gradient in all shallow wells Temperature °C The maximum thermal gradient in shallow research wells within the field is 380 °C/km.
Four production wells are currently in use and
one reinjection wellDrilled Depth
in mDepth of production casing m
Width of production casing m
Depth to pump m
Maximumproduction
L/s
Temp. of produced water °C #
Depth of main aqifers m
SN-03* 1970 1715 99 9 5/8 reinjection 15 100-105 230, 400,930, 1700
SN-04 1972 2025 172 9 5/8 136,6 35 85-114 200, 390, 1190, 1980
SN-05 1981 2207 168 135/8 121,4 25 98-109 450, 560, 700, 2100
SN-06 1985 2701 414 135/8 121,4 25 118-121 535, 900, 2070, 2400
SN-12 1994 2714 791 103/4 121,4 35 106-113 1080, 2040
SN-01 SN-02 SN-03 SN-04 SN-05 SN-06 SN-12
aq. d in m.
aq. d in m.
aq. d in m.
aq. d in m.
aq. d in m.
aq. d in m.
aq. d in m.
185 230 200
380 400 390 450
620 560 560 535
710 700
950 930 950 900
1180 1190 1080
1700
1980 2100 2070 2040
2400
About 50 L/s of 85-120 °C hot
water is produced from three
main feed zones.
A fourth feed zone with
temperatures exceeding 150
°C is probably encountered
below 2500 m depth.
About 30 % of the return water is collected and mixed
with the produced water to maintain an appropriate
distribution temperature. Any excess return water is
reinjected into an abandoned production well
Year
Pumped
Water
L/s
Temp.
pumped
water
°C
Return
water
L/s
Temp. return
water °C
Delivered
water L/s
Temp. delivered water °C
2013 49.1 106 23 35 72.6 83.22014 46.7 111 20 33 66.6 87.7
2015 50.9 103 26 35 76.0 80.9
Production data 2013-2015:
Well
SN-4
Well
SN-5
Well
SN-6
Well
SN-12
Temp. °C 108 100 118 108
pH/°C 8.34/
19
8.44/
19
8.39/
20
8.38/
22
Conduct.
S/cm
5945 5000 5210 6530
TDS mg/L 3430 2730 3200 3720
Tot. carb. as
CO2
4.9 6.2 4.5 4.4
H2S mg/L 0.21 0.22 0.26 0.13
B mg/L 0.25 0.22 0.25 0.25
SiO2 mg/L 125 116 147 103
Na mg/L 683 578 577 704
K mg/L 16.0 12.9 14.2 14.8
Mg mg/L 0.505 0.311 0.485 0.38
Ca mg/L 480 363 486 552
F mg/L 0.6 0.7 1.1 0.6
Cl mg/L 1800 1410 1650 2010
SO4 mg/L 316 244 320 332
Al mg/L 0.015 0.022 0.036 0.015
Fe mg/L 0.003 0.013 0.006 0.006
Mn mg/L 0.011 0.008 0.010 0.013
Salinity ‰ 3.2 2.5 3.0 3.6
2H ‰ -73.59 -71.55 -72.48 -70.18
18O‰ -10.47 -10.56 -10.39 -10.56
Chemical properties of the geothermal water
2H and 18O are similar to
precipitation in the
mountains some tens of km
to the north and northeast
The production characteristics of the wells have
changed with time. Pressure has declined in some
of them, changing the mixing rates of different feed
zones and the temperature of the produced fluid.
The salinity of water increased significantly with
time and increased production rate.
No indication is found of reservoir cooling due to
seawater inflow. No increase in regional drawdown
has been observed during the last 20 years, even
though the production rate has increased slightly.
Elev
atio
n a
bo
ve s
eale
vel i
n m
Observation well SN-02
The production has been sustainable during the last 20 years and not put much strain on the system. The effects of increased production have still been considered as there are:
• Plans for building new flats • Possible electricity generation in a moderate scale has been
considered• Building of spa utilizing the unique balneologic
characteristics of the water is also a possibility
Future possibilities for sustainable
increase in production have therefore
been considered lately:
The results indicate that up to 10
L/s of return water can be
reinjected on a long-term basis
with insubstantial cooling of the
production fluid.
• All existing data have been reevaluated• Two shallow exploration wells drilled • A new thermal gradient map and conceptual
model have been designed• A tracer test performed to estimate the
optimal rate of reinjection of return water into the field.
Results
Calculated groundwater elevation, concentration of chloride, tracer concentration a.o.
Input data
Well data and geological data , logging and geothermal gradient ......
Model (non calibrated)
Measurements
Measured groundwater elevation, concentration of chloride, tracer concentration
Comparison
Recalibration
Final results
Model (calibrated)Run of the model
to forcast changes due to given conditions
Use of the model
• An updated reservoir model of the field has been made taking into account the last 14 years of production.
Nine future production scenarios were calculated:
a: Same production as 2014b: 10% increase from 2014c: 20% increase from 2014
Each was calculated for three different combination of production ratio from the wells:
1: All wells used in the same ratio as in 2014 (SN-04:SN-05:SN-06:SN-12= 20:29:21:30)
2: Only use of wells SN-04 and SN-06 in the ratio of estimated maximum output (60:40)
3: Only wells SN-05 and SN-12 used in the ratio of estimated maximum output (40:60)
Case 1 production from SN-04, SN-05, SN-06 and SN-12 (20:29:21:30)
20:29:21:30
Future production scenarios: 1a (green), 1b (yellow) , 1c (red)
-160
-150
-140
-130
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
10
20
30
40
1966 1970 1974 1978 1982 1986 1990 1994 1998 2002 2006 2010 2014 2018 2022 2026 2030 2034
Vat
nsb
orð
[m
y.s
.]
Mælt Kvörðun Tilfelli 1a Tilfelli 1b Tilfelli 1c dýpt dælu
-160
-150
-140
-130
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
10
20
30
40
1966 1970 1974 1978 1982 1986 1990 1994 1998 2002 2006 2010 2014 2018 2022 2026 2030 2034
Vat
nsb
orð
[m
y.s
.]
Mælt Kvörðun Tilfelli 1a Tilfelli 1b Tilfelli 1c dýpt dælu
-160
-150
-140
-130
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
10
20
30
40
1966 1970 1974 1978 1982 1986 1990 1994 1998 2002 2006 2010 2014 2018 2022 2026 2030 2034
Vat
nsb
orð
[m
y.s
.]
Mælt Kvörðun Tilfelli 1a Tilfelli 1b Tilfelli 1c dýpt dælu
-160
-150
-140
-130
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
10
20
30
40
1966 1970 1974 1978 1982 1986 1990 1994 1998 2002 2006 2010 2014 2018 2022 2026 2030 2034
Vat
nsb
orð
[m
y.s
.]
Mælt Kvörðun Tilfelli 1a Tilfelli 1b Tilfelli 1c dýpt dælu
SN-04 SN-05
SN-06 SN-12
Drawdown in production wells
Case 2 Production from SN-04 and SN-06 (60:40)
Future production scenarios: 2a (green), 2b (yellow) , 2c (red)
-160
-150
-140
-130
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
10
20
30
40
1966 1970 1974 1978 1982 1986 1990 1994 1998 2002 2006 2010 2014 2018 2022 2026 2030 2034
Vat
nsb
orð
[m
y.s
.]
Mælt Kvörðun Tilfelli 2a Tilfelli 2b Tilfelli 2c dýpt dælu
-160
-150
-140
-130
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
10
20
30
40
1966 1970 1974 1978 1982 1986 1990 1994 1998 2002 2006 2010 2014 2018 2022 2026 2030 2034
Vat
nsb
orð
[m
y.s
.]
Mælt Kvörðun Tilfelli 2a Tilfelli 2b Tilfelli 2c dýpt dælu
-160
-150
-140
-130
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
10
20
30
40
1966 1970 1974 1978 1982 1986 1990 1994 1998 2002 2006 2010 2014 2018 2022 2026 2030 2034
Vat
nsb
orð
[m
y.s
.]
Mælt Kvörðun Tilfelli 2a Tilfelli 2b Tilfelli 2c dýpt dælu
-160
-150
-140
-130
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
10
20
30
40
1966 1970 1974 1978 1982 1986 1990 1994 1998 2002 2006 2010 2014 2018 2022 2026 2030 2034
Vat
nsb
orð
[m
y.s
.]
Mælt Kvörðun Tilfelli 2a Tilfelli 2b Tilfelli 2c dýpt dælu
SN-04SN-05
SN-06 SN-12
Drawdown in production wells
Case 3 Production from SN-05 and SN-12 (40:60)
Future production scenarios: 3a (green), 3b (yellow) , 3c (red)
-160
-150
-140
-130
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
10
20
30
40
1966 1970 1974 1978 1982 1986 1990 1994 1998 2002 2006 2010 2014 2018 2022 2026 2030 2034
Vat
nsb
orð
[m
y.s
.]
Mælt Kvörðun Tilfelli 3a Tilfelli 3b Tilfelli 3c dýpt dælu
-160
-150
-140
-130
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
10
20
30
40
1966 1970 1974 1978 1982 1986 1990 1994 1998 2002 2006 2010 2014 2018 2022 2026 2030 2034
Vat
nsb
orð
[m
y.s
.]
Mælt Kvörðun Tilfelli 3a Tilfelli 3b Tilfelli 3c dýpt dælu
-160
-150
-140
-130
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
10
20
30
40
1966 1970 1974 1978 1982 1986 1990 1994 1998 2002 2006 2010 2014 2018 2022 2026 2030 2034
Vat
nsb
orð
[m
y.s
.]
Mælt Kvörðun Tilfelli 3a Tilfelli 3b Tilfelli 3c dýpt dælu
-160
-150
-140
-130
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
10
20
30
40
1966 1970 1974 1978 1982 1986 1990 1994 1998 2002 2006 2010 2014 2018 2022 2026 2030 2034
Vat
nsb
orð
[m
y.s
.]
Mælt Kvörðun Tilfelli 3a Tilfelli 3b Tilfelli 3c dýpt dælu
SN-04 SN-05
SN-06 SN-12
Drawdown in production wells
Main results:• A 20 % increase in production over the next 20 years would
require a deepening of pumps in two of the existing production wells, but the casing depths are not a limiting factor in any of the wells.
• An even higher production increase may call for a new
production well as the casing in the two oldest wells is only at
170 m depth.
• Wells SN-05 and SN-06 have the lowest yield and may be limiting
in possible production increase.
• The future possibilities for production of the field are manifold and much care will be taken in the decision of the future exploitation of the resource
• The aim is to maintain a sustainable and environmentally sound production of the field for future generations
Thank you!
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