a1 future production from the seltjarnarnes geothermal field hrefna kristmannsdóttir

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

.]


-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

.]


-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

.]


SN-04 SN-05

SN-06 SN-12

Drawdown in production wells

Case 2 Production from SN-04 and SN-06 (60:40)


-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

.]


-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

.]


-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

.]


-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

.]


SN-04SN-05

SN-06 SN-12


Case 3 Production from SN-05 and SN-12 (40:60)


-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

.]


-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

.]


-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

.]


-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

.]


SN-04 SN-05

SN-06 SN-12


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!

a1 future production from the seltjarnarnes geothermal field hrefna kristmannsdóttir

Science