STATE OF KNOWLEDGE OF THE GEOTHERMAL PROVINCES OF REPUBLIC OF DJIBOUTI

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1 STATE OF KNOWLEDGE OF THE GEOTHERMAL PROVINCES OF REPUBLIC OF DJIBOUTI UNU training KENGEN Naivasha, Kenya, November 2007 JALLUDIN Mohamed Djibouti, CERD

2 GEOTHERMAL EXPLORATIONS IN DJIBOUTI FIRST PHASE Preliminary field studies Asal rift geophysical studies First geothermal drillings in Asal Rift geothermal area Nord-Goubhet geophysical studies SECOND PHASE Hanlé-Gaggadé exploration (field studies and gradient wells) Hanlé geothermal drillings Asal rift new drillings and geophysics Scaling and corrosion study of Asal rift deep reservoir

4 GEOLOGY AND SURFACE MANIFESTATIONS

5 HANLE GEOTHERMAL EXPLORATION AREA Republic of Djibouti Lake Asal Hanle plain Gaggade plain HANLE 1 HANLE 2 Lake Abhe

6 HANLE-GAGGADE GEOCHEMICAL STUDIES (AQUATER-CERD 1983)

7 -50 ELECTRICAL SURVEY OF HANLE PLAIN (AQUATER-CERD 1983) " Yoboki Legend -100 Altitude of the T group (resistant) -150 Disconinuity Kilometers -50 0

8 HANLE GRADIENT WELLS TEWEO1 GARABAYIS2 30 C 100 C 130 C Garabayis1 2 /100m C Teweo1 1.3 /100m 43.7 C Coarse alluvium Fine sand Mud and silt Rhyolite Basalts 452 m Garabayis2 3 /100m 80.8 C 500m

9 Depth m Depth m HANLE DRILLINGS Temperature C Temperature C HANLE 1 HANLE Alluviums Rhyolites Trachytes Basalts

10 HANLE EXPLORATION OUTCOME Hanlé 1 (1623 m), 72 C at 1420 m Hanlé 2 (2038 m), 124 C at 2020 m Permeability Hanlé 1: rhyolites, contact rhyolites-basalts, scoriae, dry below 800 m Hanlé 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

11 Asal Geothermal area Republic of Djibouti

12 SURFACE MANIFESTATIONS AND GRADIENT WELLS

13 GRAVIMETRIC SURVEY. BOUGUER ANOMALY (BRGM 1993)

14 TEM SURVEY OF THE ASAL RIFT (BRGM 1993; ORKUSTOFNUN 1988) Altitude -100m Altitude -200m Altitude -300m

15 Main geochemical results (San Juan et al. 1990) Thermal fluids result from basalt-sea water interaction This interaction is influenzed by evaporation Some hot springs could be mixed with Asal lake waters The boron anomaly in the borehole fluids suggests a vapour dominated system

16 Profondeur m Temperature profiles Asal geothermal area Température C Well Depth (m) Temp. Max ( C) Temp. Gradient ( C/100m) 1000 A A ASAL3 ASAL4 ASAL5 A A A A

17 Depth m Depth m Interpretative cross section of ASAL Asal 0 rift Geothermal area Temperature C ASAL Temperature C ASAL Asal series Stratoid series Dalha basalts m Alluviums Clays Hyaloclastites Rhyolites Basalts Trachytes 500 m 2013 m m

18 Total flow rate (ton/h) Total flow rate (ton/h) Wt (ton/h) Production curves of ASAL /8/87 20/9/87 30/10/87 9/12/ SEPT.89 DEC.89 MAR.90 Production curve of ASAL WHP (bar) WHP (bar)

19 Scale deposits in 6 inch production liner Asal 1 geothermal well (BRGM-CERD 1981) 180 µm Spharelite Sulphide deposits 300 m depth Baryte x3000 Silencer deposits Galena CERD Republic of Djibouti

20 Pressure bar ( Pi - Pwf ) / QN Drawdown bar ( Pi - Pwf ) / QN Asal 3 well testing data Drawdowns. ASAL Multirate drawdown. ASAL ton/h ton/h ton/h Time hour ton/h /QN ( (Qj-Q(j-1) * log (t-t(j-1) ) ) Injectivity test. ASAL Multirate drawdown. ASAL6 10 Time sec /QN ( (Qj - Q(j-1) * log (( t - t(j-1))

21 HYDRODYNAMIC PROPERTIES OF THE DEEP RESERVOIR IN ASAL RIFT ZONE ASAL3 Drawdown tests ASAL4 injectivity test Semilog Bilog Semilog Bilog Wt ton/h Q ton/h kh dm skin kh dm Multiple ASAL3 recovery tests Wt ton/h Q ton/h kh dm Q m3/h kh dm kh dm Injectivity After injection 0.28 ASAL6 Drawdown tests Wt ton/h Q ton/h Semilog kh dm Multiple 4.11 Multiple 6.4 skin Bilog kh dm

22 Pression à 1100 PRESSURE BUILD-UP MEASUREMENTS. ASAL ( ta + tp ) / ta Build-up décembre 1987 Build-up mars 1990

23 DEEP RESERVOIR RESULTS IN ASAL Reservoir recognized in ASAL1, ASAL3 and ASAL 6 (in the same area) Temperature 260 C to 280 C Reservoir: Dalha basalts (9-4 My), 1050 m to 1300 m ASAL 3 production: Initial characteristics: total mass flow 360 t/h for 12.5 WHP Kh: 6.3 dm TDS in the reservoir: ppm Scaling in the well (6 to 10 mm): sulphides (PbS, ZnS) Scaling in surface equipment: amorphous Si with Fe and Mn Severe decrease of production rate Decrease of bottom hole pressure ASAL INTERMEDIATE RESERVOIR Recognized in all Asal geothermal wells but not yet studied Reservoir: Top of Stratoid series and the bottom of Asal series Located between 300 m and 600 m Temperature 130 C to 190 C TDS : 50 g/l

24 ARTA (GEOTHERMICA 1982)

25 NORD-GOUBHET (BRGM 1983)

26 LAKE ABHE GEOTHERMAL PROSPECTS

27 OBOCK GEOTHERMAL PROSPECTS

28 GROUNDWATER THERMAL ANOMALIES DJIBOUTI AQUIFER

29 CONCLUSIONS HANLE-GAGGADE BASINS ZONE Drilling results not conclusive in Hanle basin Exploration by drilling not completed Need for new geophysical surveys as EM, AMT Reevaluate possibility of new drillings ASAL RIFT ZONE Deep reservoir of high enthalpy demonstrated in ASAL1 area Lateral extension of deep reservoir not yet evident Permeability and circulations controlled by fractures Major problem of scaling still to be resolved Geophysical surveys describe complex structures of reservoirs Fairly good understanding of fluid origin based on geochemistry and isotopes Shallow reservoir with medium enthalpy are preliminary and significant results The shallow reservoir is likely to have good extension

30 PERSPECTIVES FOR GEOTHERMAL DEVELOPMENT ASAL RIFT ZONE Realize exploration with drilling in the shallow reservoir Develop both reservoirs for electricity production OBOCK ZONE Realize geophysical surveys with EM and AMT methods Realize geochemical and isotopic studies on the hydrothermal manifestations Exploration drilling Feasibility study LAKE ABHE AND GAGGADE ZONES Realize geophysical surveys with EM and AMT methods Realize geochemical and isotopic studies on the hydrothermal manifestations Exploration drilling Feasibility study NORTH REGIONS OF ASAL LAKE

31 Thank you CERD

CERD STATE OF KNOWLEDGE OF THE GEOTHERMAL PROVINCES OF REPUBLIC OF DJIBOUTI. ARGEO-C1 Conference Addis-Ababa, Ethiopia, November 2006

CERD STATE OF KNOWLEDGE OF THE GEOTHERMAL PROVINCES OF REPUBLIC OF DJIBOUTI. ARGEO-C1 Conference Addis-Ababa, Ethiopia, November 2006 STATE OF KNOWLEDGE OF THE GEOTHERMAL PROVINCES OF REPUBLIC OF DJIBOUTI ARGEO-C1 Conference Addis-Ababa, Ethiopia, 24-29 November 2006 JALLUDIN Mohamed Djibouti, GEOTHERMAL EXPLORATIONS IN DJIBOUTI FIRST