Characterization and Efficiency of Intermediate Cap Rock by Using XRD and SEM-EDS from the Well Glc-1, in Asal Geothermal Field, Djibouti
Mohamed Abdillahi ADEN, Koichiro WATANABE, Thomas TINDELL
[Kyushu university/ODDEG, Japan]
This paper reports the results of X-ray diffraction mineralogical studies of the clay-rich from shallow cap-rock. The study area (Asal-field) is one of the most geothermally interesting and tectonically active structures in Djibouti. The X-ray diffraction data were treated using decomposition methods and the peaks identified were performed the investigation cap rocks of the geothermal system developed above of the intermediate reservoir. The additionally Scanning electron microscope (SEM) to this study is to enhances our knowledge and understanding fluid rock interaction in geothermal system, in order to assess the effectiveness and degree of interaction with fluid. The Scanning electron microscope (SEM) is uniquely suited for studying clays because it affords a magnified, three dimensional view to better understand the morphology and detailed information nano to micron scale scale information on crystal-crystal relationships. This clay cap deposit epoch Pleistocene is located between 292m to 421m from the well Glc-1. The upper part is composed of brown to red brown clay; the lower part is composed of grey clay with a plastic tendency. These two levels exits only Gale le Coma area but it is disappear to the northeastern, according from the well Asal-4 and Asal-5. The result of the X-ray diffraction shows quartz, plagioclase, calcite, smectite, Chlorite and interstratified mixed layer chlorite/smectite. The Chemical result of major oxides acquired from XRF analyses show that the changes in Al and Si which are the main actors in the conversion of smectite to chlorite, do not gradually increase or decrease. SEM imagery also reveals crystal-clay relationship which are important as in some setting clays attach to an alter crystal surfaces which influence permeability and rock strength. Maximum paleo-temperatures higher than 100°C are indicating hot fluid migration from the intermediate reservoir to surface.
|        Topic: Geology||Paper Number: 12124|