Third EAGE Eastern Africa Petroleum Geoscience Forum

Understanding petroleum systems within a complex region such as East Africa requires an approach that focuses on identifying controls on distribution of hydrocarbon systems, reservoir and seal, and trap history. We have defined several genetic tectono-stratigraphic domains across the East Africa offshore margin that share key hydrocarbon system characteristics whilst at the same time reflecting important spatial and temporal margin trends.

East Africa’s margin history records rifting, continental break-up and long-lived structural reactivation and rejuvenation due to far-field tectonic stresses. Continental rifted margins in the north (Somalia to Northern Mozambique) are characterized by hyper-extension and/or mantle exhumation. In contrast, magma-rich margins developed in the south between Southern Mozambique and Zululand, were influenced by the long-lived Karoo hot spot track.

The varied tectonic history observed along the margin will be discussed utilizing a series of geo-seismic transects from northern South Africa to Somalia. These will illustrate the influence that genetic margin character has on the potential for source rock deposition, reservoir and seal development, trapping styles and hydrocarbon retention.

East Africa conjugate margin evaluation has led to a greater understanding of source rock deposition and distribution as well as a detailed analysis of the similarities and differences in stratigraphic evolution offshore Somalia, Madagascar, Seychelles and West India. The transform nature of Jurassic rifting explains the differences in crustal architecture across the basins and the presence of isolated salt basins. This study also provides a good framework for play type identification in the four margins with large structural and stratigraphic traps identified and strong evidence for oil.

This study aims to improve our understanding of the predominance of accumulated gas and to identify why there is an absence of oil and where it may be preserved. To do so, all available data were integrated into a consistent geological model that was transferred into a dynamic three-dimensional petroleum systems model. Interest is focused on the Mozambique Channel basin where newly acquired, processed, and interpreted 3D seismic data have become available.

Kenya’s Shell-BG operated L10 A & B blocks contain the only offshore oil discovery on the East African margin. This discovery is encouraging for oil exploration in the region; however, uncertainty remains over the source of the oil and the extent of the source across the basin. To address this major uncertainty for the region, Shell-BG Kenya and Fugro have undertaken a geochemical survey with 5000 km2 of multibeam echosounder bathymetry and backscatter datasets, and piston cores to identify and sample macro and micro hydrocarbon seepage in the area.

Shell-BG Kenya and Fugro present here our targeted approach to Seephunting in offshore Kenya. We include the initial results from the operational phase and the lessons learned from the characterisation of a seafloor with strong bottom water currents, major fault escarpments, a volcano and deep-water sediment waves. We demonstrate the value of high-resolution multibeam in sea floor characterisation together with full integration of the available 3D seismic data. This fully integrated approach allowed for 1) efficient reduction of the number of targeted sample sites, 2) increasing the concentration of drop cores per identified seep feature and 3) increasing the chance of sampling macro or micro seepage at the site. Geochemical analysis of the piston core samples is in progress.

The survey revealed challenging seafloor conditions for Seephunting. Detailed work characterising the area and its uncertainties prior to the survey and the systematic use of exploratory piston cores to address those uncertainties during operations gave the survey the greatest chance of sampling seepage present. Shell-BG Kenya and Fugro therefore have confidence that the results will be representative of seep activity in the area and will influence the prospectivity of the region. The technical and operational learnings from Seephunting in Blocks L10A & B from the seafloor, water column and subsurface will also aid in other Seephunting endeavours in the region and elsewhere.

Need for capacity building is an immediate priority for many universities in emerging economies in which resource extraction is presumed to accelerate economic growth. A novel approach is developed between University of Dar-es-Salaam (UDSM) and University Aberdeen (UA) to give immediate growth to the pre-existing local content in petroleum geoscience and, to accesses a large number of indigenous students and academics. Appointment of dedicated lectureships at UA are tasked with developing geological programmes at UDSM. The geological programmes are research driven and, include teaching key undergraduate and post-graduate courses relevant to the hydrocarbon industry. A critical component of our approach is that, the lecturers spend approximately half the academic year in the host country. As such, they are not visitors but fully integrated academic staff in the host university, while enjoying similar status at UA. Appointments were funded by sponsorship from BG Tanzania, now part of the Shell Group. Thus far student feedback is very positive and is accompanied by strong support from the UDSM academic staff. The UA lecturers are “part of the UDSM team” and were completely integrated into the UDSM environment from day 1 thus, barriers to progress with teaching and research collaboration were effectively eliminated.

Presentation discussing Late Cretaceous to Paleogene depositional systems mapped in Block 2, Tanzania. These include slope channels, lobes and contourite drift deposits. Several reservoir levels penetrated during the exploration drilling phase will be discussed. These include slope channels, lobes and contourite drift deposits.

The South-Central Mozambique Basin is a magmatic margin that originated during the break-up of Gondwana. Until the Early Paleocene, the main sedimentary processes controlling deep-water deposition were gravitational and density currents.

The subsequent Early Tertiary Sequence (ETS) constitutes the interval of interest for this study. During the Eocene, marine passages were opened and closed around the globe ( Rebesco et al, 2014 ). This likely resulted in a change in the oceanic circulation pattern and distribution and strength of currents. In the Mozambique basin, this event coincided with a time when the deep water environments were starved of sediment supply. The combination of these two factors could have resulted in a deep water environment dominated by water-bottom current activity.

The topography of Austral and Eastern Africa (including Madagascar) is characterized by very long wavelength (several thousands of kilometers) plateaus and domes related to mantle dynamics: the Southern (Kalahari) Plateau, the Eastern (Kenyan) African and Ethiopian Domes and Madagascar Plateau.

Our objective here is to discuss the relationships between the plateaus and domes growth since Early Cretaceous times, the climate (and mainly the precipitation) changes and the sediment supply along the passive margins.

The reconstruction of the depositional history of the Paleogene succession from wells drilled in Area 4, offshore Mozambique, was carried out by interpreting paleoecological signals from integrated paleontological and non-paleontological datasets.

A high-resolution integrated biostratigraphic framework was realized. Empirical indices based on palynomorphs, foraminifera and calcareous nannofossils were derived from this study and integrated with the lithological log curves and the mineralogical dataset. Inferences were made in terms of paleo-temperature, bathymetry, distance from the coastline, intensity of surface runoff and fluvial discharge into the sea. Connections among global climatic trends, tectonic uplift of the hinterland, eustatic cycles, sediment accumulation and turbidite deposition in deep marine settings have been extensively investigated.