The geothermal reservoir Groß Schönebeck- on the way to power production

in the North German Basin -

G. Zimmermann, U. Trautwein, H.-G. Holl, S. Köhler, B. Legarth, A. Saadat, H. Winter & E. Huenges

outline

- introduction- proppant frac treatment 2002- massive water frac treatment 2003 I + II- flow-back test 2003 I + II- conclusion and outlook

geothermal reservoir Groß Schönebeck

technology development forgeothermal power production

1. milestone january 2001:• temperature > 150 °C• depth > 4 km

2. milestone march 2002: • flow rates > 25 m³/h

3. milestone december 2003:• flow rates > 50 m³/h• prod.-index > 10 m³/(h MPa)

4. next step:• 2. well (doublet system)

geology of the Central European Basement

Paris

Bruxelles

London

Munich

Praha

Warszawa

Berlin

Hamburg

Kobenhavn

NEGB PTNWGBNEB

DB

North Sea

Baltic

Sea

Rotliegend

Tornquist zone

VariszicanbeltVariszican Deformation front

Caledonian Deformation front

Caledonides &older massifs

Precambriancrystallinebasement

Alps

Rhenohercynian

Saxothuringian

Moldanubian

Alpi

ne

front

0 100 200 km

after Ziegler 1990, Bertelsen 1992, Plein 1993, Beneck et al. 1996

drill site Gr Sk 3/90

lithology, porosity and permeabilityD

epth

(m)

0

500

1000

1500

2500

3000

2000

3500

4000

CenocoicCretaceousJurassic

Triassic

Zechstein

Rotliegend

Depth 4294 m

Sandstone ConglomerateSiltstone Volcanics

3900

4000

4100

4200

Depth 4240 m (1990)4294 m (2000)

Zechstein

Mellin

Peckensen

Eldena

Rambow

Havel

0 10 20

POROSITY (%)

0,001 1 1000PERMEABILITY (mD)LITHOLOGY

n = 200

Sandstone ConglomerateSiltstone Volcanics

3900

4000

4100

4200

Depth 4240 m (1990)4294 m (2000)

Zechstein

Mellin

Peckensen

Eldena

Rambow

Havel

0 10 20

POROSITY (%)

0,001 1 1000PERMEABILITY (mD)LITHOLOGY

n = 200

hydraulic stimulation of sandstones February 2002

qi

pwhpat

Open Hole Packer

7“ Liner

3 ½“ Fracstring

9 5/8“ Casing

5“ Fracstring

p,TMemory Fracinterval5 7/8“

OH-Interval

3874 m

4294 m

2309 m

Sand Plug

Expansion Joints

dzdpRRf

dzdpslurry

concept:

• open-hole stimulation

• high-viscous fluid(HTU-Gel + citric acid)

• proppant

result:

• increase of productivity

• not sufficient for economics

Legarth et al., Geothermics, 2003

SH:18,5°±3,7

Holl et al. EAGE, 2004

dept

h[ m

]

cumulative flow [ m3/h ]

logging after stimulation sandstones

flow back test march 2003

0

5

10

15

20

25

30

0 5000 10000 15000 20000 25000

time [sec]

flow

[l/s

]

0

20

40

60

80

100

120

140

160

180

head

pre

ssur

e [b

ar]

head pressure

flow

productivity indexPI = 3-4 m³/(h MPa)

FMI measurements after 1. waterfrac treatment

Holl et al. EAGE, 2004

dept

h[ m

]

4127

4128

perforated liner installed beneath 4135 m

massive waterfrac treatment fall 2003

production test Groß Schönebeck 1.12.03

production test (flow back) december 2003

0

0,2

0,4

0,6

0,8

1

1,2

0 500 1000 1500 2000time, min

flow

, m³/m

in

0

20

40

60

80

100

120

head

pre

ssur

e, b

ar

flow

pressure

production test (flow back) Groß Schönebeck 1.12.03

fracture closureat 96,5 bar

80

85

90

95

100

105

110

115

120

26500 28500 30500 32500 34500 36500 38500 40500 42500

time, s

head

pre

ssur

e, b

ar

0

0,2

0,4

0,6

0,8

1

1,2

flow

rate

, m³/m

in

PI > 14 m³/h MPa PI < 14 m³/h MPa

flow back test december 2003

0,8

1

1,2

1,4

1,6

2,7 2,9 3,1 3,3 3,5 3,7 3,9 4,1 4,3

log time (sec)

log

(diff

eren

tial p

ress

ure

(bar

))

bilinear flow ( ~ t0,25)

formation linear flow (~ t 0,5)

fractureclosure

according to Cinco-Ley & SamaniegoSPE 1981

Conclusionlearning curve „enhancing productivity“

Primary testJan. 2001passive

sandstonefracFeb. 2002gel and proppant100m3

40 l/s

waterfracFeb. 2003water4000 m3

25 l/s

waterfracNov./Dez. 2003water10000 m3

40 l/s (80 l/s)

fracfluidvolumemax. rate

prod

uctiv

ity in

dex

[ m/h

MP

a ]

3

15

10

5

conclusion and outlook

- increase of productivity- no sustainable PI -> tie-back with proppant

- use this well as injection well- design of 2nd well for doublet system