Geochemical Interpretation of Boreholes Waters from Ambado-PK 20 Area, Djibouti
DAHER Ali Hassan, IDIL Souleiman Bouraleh
The Ambado-Pk20 field is located in the centre of the Republic of Djibouti, this area is affected by faults and dominates by several types of formation such as the basaltic and rhyolite series. In this area, there are not surface manifestations but the water wells have high temperatures. Geochemical study is focused on sampling and analysis (physico-chemical, trace elements and isotopes) of twenty-six boreholes in the PK 12, PK 20, Nagad, Douda, Damerjog and Ali Ouné sectors. The chemical characteristics of water wells in the Ambado-PK-20 study area are generally Cl-HCO3-Na type and are low mineralized at PK 20 but high mineralized at Nagad, Douda and Damerjog. The nature of the water wells may be from the groundwater (superficial water). The silica geothermometer and cation geothermometer give relatively wide temperature values. This can be explained by the fact that these water wells are immature and therefore classic geothermometers cannot be applied in this study. Thus the reservoir temperature cannot be estimated. The stable isotopic (δD and δ18O) composition and Cl/B ratio were used to determine the origin of the water. The water wells are meteoric waters from the superficial water and they are not mixed with the sea water. In order to improve this study, it is recommended to make a temperature gradient or logging of the boreholes and also to do additional analyses to estimate the reservoir temperature.
|        Topic: Geochemistry||Paper Number: 14136|