Evaluation of Structural Permeability of the Northern Lake Abaya Geothermal Field, Southern Main Ethiopian Rift, Using CO2 Flux Measurement
[Geological Survey of Ethiopia, Ethiopia]
The northern Lake Abaya area is located in the southern part of the Main Ethiopian Rift (MER) about 275 km SSW of Addis Ababa on the all-weather Addis Ababa – Arba Minch road. The main objective of the present work is to conduct detailed geoscientific studies for geothermal resource characterization and evaluation of structural permeability in the Northern Lake Abaya Geothermal field using geological and structural mapping, fluid chemical analysis, and soil temperature and CO2 flux measurement. After an initial phase of basin subsidence related to slip along large boundary faults, the Quaternary-recent volcano-tectonic activity of the MER is typically associated with dense fault swarms affecting the rift floor. These fault systems, referred to as Wonji Fault Belt (WFB), characterize the MER and are located at the rift axis. The dense fault network characterizing the WFB allows deep fluid circulation at major volcanic centers, and development of promising geothermal resources, such as the Northern Lake Abaya Geothermal Field. Permeable structures will be identified with the aid of a soil gas flux and soil heat flux survey. Soil gas flux and soil temperature will be measured at predefined profiles at fixed intervals, perpendicular to the fault structure to identify if a flux anomaly can be detected. The soil gas and heat flow survey of the Northern Lake Abaya geothermal field will consist of ~ 250 direct measurements of CO2 flux and soil temperature. Portable flux equipment designed for surveying CO2 flux has been commercially available since the late1990’s. This paper discusses the use of soil CO2 flux measurement in evaluation of structural permeability in the Northern Lake Abaya geothermal field, MER.
|        Topic: Geology||Paper Number: 12002|