PRESENTED BY Ayan AHMED SUGE Geologist Geothermal Sites In - - PowerPoint PPT Presentation

ASAL Gale-le-Koma Current Surveys

PRESENTED BY Ayan AHMED SUGE Geologist

Geothermal Sites In Republic of DJIBOUTI

Geother Geothermal mal sites sites

• 1. Lake Abhe
• 12. Nord Ghoubbet (Afaî-

Bolli Daar)

• 2. Sakalol
• 13. NE Ghoubet (Assa Foo)
• 3. Arta
• 14. Modayto (N Gaggade)
• 4. Asal Fialé
• 15. Obock
• 5. Asal gale-le-koma
• 16. Okililaeou (SE Gaggade)
• 6. Balho
• 17. PK 20-Ambado
• 7. Daggadé (W hanlé)
• 18. Roueli
• 8. Dimbir-Didir (W

Gaggade)

• 19. Sakalol
• 9. Garabayyis ( E

Hanlé)

• 20. Tadjoura
• 10. Karapti-san
• 21. Agna-Galafi (NW

Hanlé)

• 11. Manda Inakir
• 22. Sud Est Ghoubbet

ASAL Gale-le-Koma Current Surveys

• The most popular site in the World
• The Lake Asal is the only lake that is

situated 157m below the sea level

• A lot of studies from 70’s to 80’s and a

new drilling was done in 2016.

Hydrogeologic : supply of seawater from the Ghoubbet with flow to Lake Asal ( red and blue arrrow shows movement of hot and cold water)

ASAL and Gale-Le-Koma Current Surveys

 The best-studied site in the country for 50 years (BRGM,CNRS,AQUATER,REI/ISOR);volcanology,tect

• nics,hydrogeochemistry,geophysics(MT,gravimetre,seis

micity), 6 reconnaissance holes made on Asal including A5 at the edge of the Fialé caldera. Heat source: magmatic chamber (1200 ° C to 3-5 km); good permeability; which cooled the geothermal reservoir (1978-1987) reheated since filling the magma chamber between 1988 and 2001

Geology : Fault Rift Assal NW-SE, NNW normal

fault from an older Rift

• E-W fracture mainly parallel to the Aden Ridge

Carracteristic of the reservoir

• Reservoir is situated betwen 300-1500 mètre
• Temperature : 130°C to 190°C
• Sea water flowing from the sea to Assal Lake

Geology

A1 A3 GLC-1 A6 A2 A4 A5

Geophysics study

Good conductors identified by geophysics (TDEM and MT). shallow reservoir (300-600 m) at 120-140 °C salinity is around 50g/l. Based on the old and the update studies from ODDEG, the location of Gale Le Goma GLC1 drilling well was determinate close to Assal 3

 H

NE-SW cross section through the Assal rift zone An up-flow is expected to be beneath the Lava Lake and outflow to south and west at 200-500 m depth. The up-flow zone is composed by anhydrite or other hydrothermal alteration minerals. The blue rectangles represent leaky zones where inflow of cold water from east (from the ocean) has cooled the rock at ~600-1000 m depth. Shallow reservoir between 500-700m.

ASAL and Gale-Le-Koma Conceptuel model

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PK-20 AMBADO Current Surveys

Temperature

• f the

Reservoir T˚C min T˚C max Temp. Estimated 103˚C 119˚C Temperature

• f water well

42˚C 73,6˚C Geophysics Geochemestr ist Geologist Technicians 7 3 6 10 Team for this Study Geographycal Location 11°28’09 ; 43°00’18 Acces road: close to the city Local developpement: urbanisation and connect directly to the electrical connexion( PAM, Port, Free zone PK20)

Geological Study

Correlation Correlation of well water drilling: Awrolofoul 6, 2, 5 Aw6= 73,6 ˚C at 114,43 Aw5= 30m3/h Aw2= 56.2 ˚C at 98m The region is affected by NW-SE ,WEN-ENE and N-S faults. The convective hydrothermal system which has warmed the surface water table in the basalts of the Gulf, but no particular surface manifestation ( Blind geothermal system). We found that the water from water wells are getting hot when 2 systems of junction of faults NW-SE and E- W

Geochimical Study

• The team take a sampling from 26 drilling

wells in the prospect zone of PK20Ambado.

• The samples was analyzis in collaboration

with BGR.

• The composition of the water have a

presence of sodium chloride. The analysis of the water revelated that the water is immature and so the geothermometer is not applicated to estimate the reservoir temperature. But from the old studies, the geothermometers indicate a temperature around 103-119°C

Geophysical Study

• The area of the propect project

was found a thermic anomalies because of the hot temperature from the drilling wells was.

• This map indicate the gravimetric
• n the MT station.

Carte de localisation des sondages MT et gravimétrie. En étoiles rouges les points MT et les points noirs les sondages gravimétriques. Les triangles bleus clairs correspondent aux forages d'eau présentant une anomalie thermique.

Conceptuel Model of the prospect project PK20Ambado

• Thermical Anomalie was
• bserve from the water

wells.(orange)

• MT revelated a conductor

anomalie with the gravimetric data (blue)

• This data revelated also a

negative residuelle anomalie

• Finaly this 3 anomalies put

together give us a sector that we selected for the exploration drilling well.

MT and Gravimetric results

Anomaly gravimetric and MT combined are found in the same location around the zone

• f Awrolofoul at PK20 Ambado.

The temperature are high in the junction beteween the Gulf Basalt and Somali Basalt. The recharge of the reservoir is coming from a meteoric water of the river. 3Drilling well are planned in 2018.

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