The East African Rift System, Targeting Hydrocarbon Exploration Using Earth Observation Data

East Africa, overlooked in terms of its hydrocarbon potential for many years, is currently experiencing a surge in interest with recent discoveries in the Albertine Rift and offshore Tanzania. This paper summarises the results of a geological interpretation study of the East African Rift System (EARS) based on Earth Observation (EO) data, incorporating both a structural and stratigraphic interpretation together with the identification of lake and offshore oil seeps. The study represents a unique, integrated and consistent interpretation over the entire EARS at a regional scale to aid exploration for energy resources. Findings from this study are presented in relation to the hydrocarbon prospectivity of the area.

The EARS is an elongate system of extensional faults, extending 5000km in a general N-S direction, and is characterised by two rifting trends defined as the Eastern and Western Branches from the triple plate junction of the Afar Triangle in Ethiopia to the Inhambane region in Mozambique. Dominated by extensional faulting, the area is characterised by two main rifting trends, defined as the Eastern and Western Branches, with several phases of superimposed rifting having occurred. Carried out at between 1:100,000 to 1:500,000 scale the study covers an area of approximately four and a half million square kilometres.

Two main remote sensing datasets are used in this study; orthorectified Landsat 7 ETM + mosaics in a 742 (RGB) pseudo-colour composite band combination with a resolution of 15m and the Shuttle Radar Topographic Mission (SRTM) 90m Digital Elevation Model (DEM).

Additional datasets have also been incorporated including an extract from Astrium’s global oil seeps database, which includes oil slicks derived from natural lake bed oil seeps of the EARS and from the sea bed of surrounding offshore areas, identified using Radar Imagery. The offshore areas include the Gulf of Aden, Seychelles, Madagascar, Somalia, Tanzania, Mozambique and Kenya, with over 800 radar scenes assessed and over 500 separate slick points recognised.

The oil seeps identified by this study, in the rift lakes of Lake Tanganyika, Edward and Nyasa (Malawi), may indicate the presence of a similar petroleum play involving the Tertiary sections as discovered recently at Lake Albert. Additionally, for the lakes in the south, there is the potential for the seeps to be derived from older Karoo sediments common in the southern part of the EARS.

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California