CERD GEOTHERMAL EXPLORATIONS AND RESULTS IN THE REPUBLIC OF DJIBOUTI. Short Course Naivasha, Kenya, November 2006

Transcription

1 GEOTHERMAL EXPLORATIONS AND RESULTS IN THE REPUBLIC OF DJIBOUTI Short Course Naivasha, Kenya, November 2006 JALLUDIN Mohamed Djibouti, CERD

2 PRESENTATION PLAN General geological and hydrothermal activity data General methodological approach Hanle graben exploration Asal rift zone exploration

3 WHAT ELEMENTS GUIDED GEOTHERMAL EXPLORATIONS Very early earth sciences observations Geological features: formations, fractures Geodynamical situation: exceptionnal plate tectonic activity Surface manifestations: current and past hydrothermal activities

4 GEOLOGICAL MAP OF THE REPUBLIC OF DJIBOUTI DREYFUS 1931

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6 GEOLOGY AND SURFACE MANIFESTATIONS CERD

7 WAYS TO GO FORWARD WITH EXPLORATION Surface and semi-surface exploration Geology, geological mapping, fracture network studies surface manifestations geochemistry Geology, geological mapping, fracture network studies surface manifestations geochemistry + geophysics Geology, geological mapping, fracture network sutdies surface manifestations geochemistry + geophysics + gradient wells Drillings, testing, reservoir engineering, analysis

8 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 ARGEO PROJECT PHASE

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10 HANLE-GAGGADE GEOCHEMICAL STUDIES (AQUATER-CERD 1983) SO4 + Cl Na + K Ca + Mg HCO3 1. Bicarbonated-earth-alcaline 4. Chlorinated-bicarbonated-sulfated-alcaline 2. Chlorinated-alcaline Mixing of groupe 1 and 4 3. Chlorinated-alcaline-earth-alcaline

11 ELECTRICAL SURVEY OF HANLE PLAIN (AQUATER-CERD 1983) CERD

12 HANLE GRADIENT WELLS CERD 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

13 HANLE DRILLINGS CERD Temperature C Temperature C HANLE 1 HANLE Depth m Alluviums Rhyolites Trachytes Basalts Depth m

14 HANLE EXPLORATION OUTCOMES 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

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16 GRAVIMETRIC SURVEY. BOUGUER ANOMALY (BRGM 1993) CERD

17 AMT SURVEY OF THE ASAL RIFT (BRGM 1993) CERD

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

19 LOOP-LOOP METHOD (ORKUSTOFNUN 1988) 300m NE A4 A1 A3 SW -500m 1 km High resistivity below low resistivity layer > 100 ohm.m ohm.m 4 10 ohm.m < 4 ohm.m

20 SURFACE MANIFESTATIONS AND GRADIENT WELLS. ASAL RIFT (BRGM-CERD 1973) CERD

21 Br VERSUS Cl IN ASAL RIFT ZONE 4 4 Br (mm) 8 3 Lake Asal Sea water Deep reservoir 2 Shallow reservoir Korili spring 1 Other springs Cl (M) 1 2

22 MAJOR ELEMENTS VERSUS Li (San Juan et al. 1990) CERD Mg/Cl.10 Ca/Cl Li/Cl.10 4 Li/Cl Na/Cl Lake Asal Sea water Deep reservoir Shallow reservoir Korili spring Other springs Li/Cl

23 δ 18 O VERSUS δd IN ASAL RIFT AREA +15 δ 18 O δd=8δ 18 O+10 Sakalol Korili Hot springs Cold springs Lake Asal 1974 Lake Asal 1979 Sea water -25 δd -5 +4

24 Temperature C Temperature C ASAL 1 ASAL Depth m Alluviums Clays Hyaloclastites Rhyolites Basalts Depth m

25 Temperature profiles Asal geothermal area Température C Well Depth (m) Temp. Max ( C) Temp. Gradient ( C/100m) Profondeur m A1 A2 A3 A ASAL3 ASAL4 ASAL5 A5 A

26 Interpretative section accross the Asal rift Geothermal area CERD ASAL 3 ASAL4 ASAL 5 Asal series Stratoid series Dalha basalts 1316 m Alluviums Clays Hyaloclastites Rhyolites Basalts Trachytes 500 m 2013 m 2105 m

27 Production curves of ASAL 3 CERD Wt (ton/h) /8/87 20/9/87 30/10/87 9/12/87 Total flow rate (ton/h) SEPT DEC MAR WHP (bar) Total flow rate (ton/h) Production curve of ASAL WHP (bar)

28 Scale deposits in 6 inches production line Asal 1 geothermal well (BRGM-CERD 1981) CERD CERD Republic of Djibouti

29 Asal 3 well testing data Drawdowns Multirate drawdown Drawdown bar ton/h ton/h ton/h ton/h ( Pi - Pwf ) / QN Time hour /QN ( (Qj-Q(j-1) * log (t-t(j-1) ) )

30 Asal 4 AND ASAL6 WELL TEST DATA Injectivity test. ASAL4 52 Multirate drawdown. ASAL Pressure bar Time sec ( Pi - Pwf ) / QN /QN ( (Qj - Q(j-1) * log (( t - t(j-1))

31 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 Q m3/h kh dm kh dm Injectivity Multiple 15.9 After injection ASAL6 Drawdown tests ASAL3 recovery tests Wt ton/h Q ton/h kh dm Wt ton/h Multiple Q ton/h Semilog kh dm 4.11 skin Bilog kh dm Multiple

32 PRESSURE BUILD-UP AT THE END OF THE FIRST PHASE AND THE SECOND PHASE PRODUCTION. ASAL3 CERD ( ta + tp ) / ta Pression à 1100 Build-up décembre 1987 Build-up mars 1990

33 PRESSURE AT 1100 m DEPTH. WELL ASAL3 CERD 84 Pressure at 1100 m depth Bar Total flow ton/h 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

34 DEEP RESERVOIR RESULTS IN ASAL Reservoir recognized by 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 the production rate Decrease of the bottom hole pressure: 3.5 bars

35 ASAL INTERMEDIATE RESERVOIR Recognized on 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

36 NORD-GOUBHET AND ARTA GEOPHYSICAL SURVEYS (BRGM 1983; GEOTHERMICA 1982) CERD

37 LAKE ABHE AND OBOCK GEOTHERMAL SITES CERD

38 GROUNDWATER THERMAL ANOMALIES DJIBOUTI AQUIFER DJIBOUTI ARTA Legend Wells Kilometers

39 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 controled by fractures Major problem of scaling still to resolve Geophysical surveys describe complex structures of reservoirs Fairly good understanding of fluids origins based on geochemistry and isotopes Shallow reservoir medium enthalpy preliminary significant results Shallow reservoir likely to have good extension

40 PERSPECTIVES FOR GEOTHERMAL DEVELOPMENT ASAL RIFT ZONE Complete exploration for the deep reservoir extension Solutions for the scaling problem of the deep reservoir Complete EM survey of Asal rift zone Study faisability of the mineral extraction from the deep reservoir high TDS fluid Realize exploration with drillings 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 drillings Faisability study LAKE ABHE AND GAGGADE ZONES Realize geophysical surveys with EM and AMT methods Realize geochemical and isotopic studies on the hydrothermal manifestations Exploration drillings Faisability study

41 Thank you CERD