STATE OF KNOWLEDGE OF THEGEOTHERMAL PROVINCES OFREPUBLIC OF DJIBOUTI

ARGEO-C1 ConferenceAddis-Ababa, Ethiopia, 24-29 November 2006

JALLUDIN MohamedDjibouti, CERD

CERD

FIRST PHASEPreliminary field studiesAsal rift geophysical studiesFirst geothermal drillings in Asal Rift geothermal areaNord-Goubhet geophysical studies

SECOND PHASEHanlé-Gaggadé exploration (field studies and gradient wells)Hanlé geothermal drillingsAsal rift new drillings and geophysicsScaling and corrosion study of Asal rift deep reservoir

ARGEO PROJECT PHASE

GEOTHERMAL EXPLORATIONS IN DJIBOUTI

CERD

CERD

GEOLOGY AND SURFACE MANIFESTATIONSCERD

HANLE 1HANLE 2

HANLE GEOTHERMALEXPLORATION AREARepublic of Djibouti

Hanle plain

Lake Abhe

Lake Asal

CERD

Gaggade plain

CERDHANLE-GAGGADE GEOCHEMICAL STUDIES (AQUATER-CERD 1983)

CERDELECTRICAL SURVEY OF HANLE PLAIN (AQUATER-CERD 1983)

"

0

-50

-200

50

-150-1

00-250

-50

-50

-50

-50

-100

-150

0

-150-100

0

-50

0

Yoboki

Legend

Altitude of the T group (resistant)

Disconinuity

3 0 31.5 Kilometers

CERDHANLE GRADIENT WELLS

452 m

Coarse alluvium

Fine sand

Mud and silt

Rhyolite

Basalts

TEWEO1 GARABAYIS2

Teweo11.3°/100m43.7°C

Garabayis23°/100m80.8°C

Garabayis12°/100m121.7°C

500m

130°C30°C 100°C

0

100

200

300

400

500

600

700

800

900

1000

1100

1200

1300

1400

1500

1600

1700

40 50 60 70 80 90

Temperature °C

Dept

h m

0

100

200

300

400

500

600

700

800

900

1000

1100

1200

1300

1400

1500

1600

1700

1800

1900

2000

2100

70 80 90 100 110 120 130

Temperature °C

Dept

h m

Alluviums

Rhyolites

Trachytes

Basalts

HANLE 1 HANLE 2

CERDHANLE DRILLINGS

Hanlé 1 (1623 m), 72 °C at 1420 m

Hanlé 2 (2038 m), 124 °C at 2020 m

PermeabilityHanlé 1: rhyolites, contact rhyolites-basalts, scoriae, dry below 800 mHanlé 2: basalts, scoriae, dry below 450 m

Bottom hole core of Hanlé 2: 18.8 My

Thick crust with 24 °C/km to 36 °C/km

HANLE EXPLORATION OUTCOMES

CERD

Asal Geothermal areaRepublic of Djibouti

CERD

CERDSURFACE MANIFESTATIONS ANDGRADIENT WELLS. ASAL RIFT (BRGM-CERD 1973)

CERDGRAVIMETRIC SURVEY. BOUGUER ANOMALY (BRGM 1993)

CERDAMT SURVEY OF THE ASAL RIFT (BRGM 1993)

Altitude -100m

Altitude -300m

Altitude -200m

CERD

Altitude -100m

Altitude -300m

Altitude -200m

EM SURVEY OF THE ASAL RIFT (BRGM 1993; ORKUSTOFNUN 1988)

CERD

Cl (M)

Br (mM)

1

4

3

2

1

4

8

2

Lake Asal

Sea water

Deep reservoir

Shallow reservoir

Korili spring

Other springs

Br VERSUS Cl IN ASAL RIFT ZONE

CERD

Lake Asal

Sea water

Deep reservoir

Shallow reservoir

Korili spring

Other springs

Ca/Cl.10

Li/Cl.104

1.5

0.5

1

1.5 7.5

Na/Cl.10

Li/Cl.104

7.552.5

5

6

7

8

Mg/Cl.10

Li/Cl.104

7.552.5

0.5

1

MAJOR ELEMENTS VERSUS Li (San Juan et al. 1990)

δD=8δ1

8 O+10

Hot springsCold springsLake Asal 1974Lake Asal 1979Sea water

Sakalol

Korili

-5

+15

-25

+4

δ18O

δD

δ18O VERSUS δD IN ASAL RIFT AREA

CERD

0

500

1000

1500

2000

2500

0 100 200 300 400Température °C

Pro

fond

eur m

ASAL3ASAL4ASAL5

Temperature profiles – Asal geothermal area

CERD

Well Depth(m)

Temp. Max (°C)

Temp. Gradient(°C/100m)

A1 1145 261 18

A2 1554 235 14.3

A3 1316 280 15.51

A4 2013 345 15.2

A5 2105 360 15.2

A6 1761 280 12.75

1316 m

2013 m

2105 m

ASAL 5ASAL4ASAL 3

Asal series

Stratoid series

Dalha basalts

Alluviums

Clays

Hyaloclastites

Rhyolites

Basalts

Trachytes500 m

Interpretative cross section ofAsal rift Geothermal area

CERD

0

50

100

150

200

250

300

350

400

11/8/87 20/9/87 30/10/87 9/12/87

Wt (

ton/

h)

Production curves of ASAL 3

0

50

100

150

200

250

300

350

10 12 14 16 18 20 22

WHP (bar)

Tota

l flo

w ra

te (t

on/h

)

SEPT.89

DEC.89

MAR.90

0

20

40

60

80

100

5 10 15 20

WHP (bar)To

tal f

low

rate

(ton

/h)

Production curve of ASAL 1

CERD

Scale deposits in 6 inches production lineAsal 1 geothermal well (BRGM-CERD 1981)

CERD – Republic of Djibouti

CERD

180 µm

Spharelite

Galena

Baryte x3000Silencerdeposits

Sulphidedeposits300 m depth

Asal 3 well testing dataCERD

0

0.5

1

1.5

2

2.50.01 0.1 1 10 100

Time hour

Dra

wdo

wn

bar

155-225 ton/h300-357 ton/h

79-130 ton/h225-300 ton/h

50

60

70

80

90

100

110

120

130

3 4 5 6 7 8

1/QN ( (Qj-Q(j-1) * log (t-t(j-1) ) )

( Pi -

Pw

f ) /

QN

Drawdowns. ASAL3 Multirate drawdown. ASAL3

0

10

20

30

40

50

100 1000 10000

Time sec

Pre

ssur

e ba

r

500

550

600

650

700

750

800

5.8 5.9 6 6.1 6.2 6.3 6.4

1/QN ( (Qj - Q(j-1) * log (( t - t(j-1))

( Pi -

Pw

f ) /

QN

Injectivity test. ASAL4 Multirate drawdown. ASAL6

CERDHYDRODYNAMIC PROPERTIES OF THE DEEP RESERVOIR IN ASAL RIFT ZONE

Semilog Bilog

Wtton/h

ΔQton/h

khdm

skin khdm

79 - 130 51 15.6 - 5 15.6Multiple 15.9

155 - 225 70 15.75.7

- 5- 5

166

225 - 300 75 6300 - 357 57 13.4 - 5 13.4

5.88787 - 0

7.3357357 - 0

khdm

ΔQton/h

Wtton/h

BilogSemilog

After injection

Injectivity

0.28

0.70.670

khdm

khdm

Qm3/h

BilogSemilog

3.7106.913.165.2 - 78.3

6.4Multiple

4.11Multiple

khdm

skinkhdm

ΔQton/h

Wtton/h

ASAL3 recovery tests

ASAL3 Drawdown tests ASAL4 injectivity test

ASAL6 Drawdown tests

CERD

74

75

76

77

78

79

80

81

82

1 10 100 1000 10000 100000

Build-up décembre 1987 Build-up mars 1990

Pres

sion

à 1

100

( ta + tp ) / ta

PRESSURE BUILD-UP MEASUREMENTS. ASAL3

70

72

74

76

78

80

82

84

0 50 100 150 200 250 300

Total flow ton/h

Pre

ssur

e at

110

0 m

dep

th B

ar

Production 1rst period of 1rst phase

Production 2nd period of 1rst phase

Production 2nd phase

Before production 1rst phase

77 days after stop production phase 1

Before production phase 2

Pressure build up after stop fo phase 2 production

Estimated by build-up after phase 2

Reservoir recognized by ASAL1, ASAL3 and ASAL 6 in the same areaTemperature 260 °C to 280 °CReservoir: Dalha basalts (9 - 4 My), 1050 m to 1300 mASAL 3 production:

Initial characteristics: total mass flow 360 t/h for 12.5 WHPKh: 6.3 dmTDS in the reservoir: 116 000 ppmScaling in the well (6 to 10 mm): sulphides (PbS, ZnS)Scaling in surface equipment: amorphous Si with Fe and MnSevere decrease of the production rateDecrease of the bottom hole pressure: 3.5 bars

DEEP RESERVOIR RESULTS IN ASAL

CERD

Recognized on all Asal geothermal wells but not yet studiedReservoir: Top of Stratoid series and the bottom of Asal seriesLocated between 300 m and 600 mTemperature 130 °C to 190 °CTDS : 50 g/l

ASAL INTERMEDIATE RESERVOIR

NORD-GOUBHET AND ARTAGEOPHYSICAL SURVEYS (BRGM 1983; GEOTHERMICA 1982)

CERD

CERD

LAKE ABHE AND OBOCK GEOTHERMAL PROSPECTS

CERDGROUNDWATER THERMAL ANOMALIESDJIBOUTI AQUIFER

CERD

HANLE-GAGGADE BASINS ZONEDrilling results not conclusive in Hanle basinExploration by drilling not completedNeed for new geophysical surveys as EM, AMTReevaluate possibility of new drillings

ASAL RIFT ZONEDeep reservoir of high enthalpy demonstrated in ASAL1 areaLateral extension of deep reservoir not yet evidentPermeability and circulations controled by fracturesMajor problem of scaling still to resolveGeophysical surveys describe complex structures of reservoirs Fairly good understanding of fluids origins based on geochemistry and isotopes

Shallow reservoir medium enthalpy preliminary significant resultsShallow reservoir likely to have good extension

CONCLUSIONS

ASAL RIFT ZONEComplete exploration for the deep reservoir extensionSolutions for the scaling problem of the deep reservoirComplete EM survey of Asal rift zoneStudy faisability of the mineral extraction from the deep reservoir high TDS fluidRealize exploration with drillings in the shallow reservoirDevelop both reservoirs for electricity production

OBOCK ZONERealize geophysical surveys with EM and AMT methodsRealize geochemical and isotopic studies on the hydrothermal manifestationsExploration drillingsFaisability study

LAKE ABHE AND GAGGADE ZONESRealize geophysical surveys with EM and AMT methodsRealize geochemical and isotopic studies on the hydrothermal manifestationsExploration drillingsFaisability study

PERSPECTIVES FOR GEOTHERMAL DEVELOPMENT

CERD

CERD

Thank you