Tectonic Framework and Petroleum Systems of the East Africa and Conjugate Madagascar Continental Margins Revealed by New PSDM Seismic
Al Danforth1, Barbara Radovich2, Don Riorah3, Halfani R. Halfani4, Elise Razaka5, Sujata Venkatraman6, and Peter Wakeling7
1Independent Consultant, Houston, TX
2Silver Grass Enterprises, Sugar Land, TX
3Chief Geologist, Ministry of Energy, Nairobi, Kenya
4Director of Exploration and Production & Technical Services, TPDC, Dar es Salaam, Tanzania
5OMNIS, Antananarivo, Madagascar
6GX Technology, Houston, TX
7GX Technology, UK, London, United Kingdom
Presented here are the results of a regional seismic program of East Africa offshore. This phase, in Kenya, Tanzania and Madagascar, is part of a campaign to cover East Africa and its conjugate margins around the western Indian Ocean. The goal of the survey is to establish a regional framework of high quality regional seismic to improve understanding of petroleum systems; the program is a collaborative effort between sponsoring companies and host governments, operated by GX Technology.
The new regional seismic lines extend up to 300 kms beyond and deeper (16 secs twt) than previous seismic coverage. The pre-stack depth images (PSDM) remove effects of the water bottom plunge at the continental rise enabling carrying major sequences from dsdp control in deep water to key wells on the shelf and also imaging beneath salt (in Majunga Basin) and volcanoes in the ultradeep area.
Sediment thickness is greater (12 kms) along the East African coast than previously reported. Large scale fans with reservoir potential in Cretaceous and Tertiary sequences extend far offshore, beyond previous seismic and existing concessions. Postulated Jurassic source rocks are deeply buried near the coast but are at appropriate depth for generating hydrocarbons over large areas of the East Africa margin. Even over oceanic crust, structural traps are indicated as are vertical migration avenues along faults associated with fracture zones. Surprisingly, the volcanoes of the ultra-deep water are observed to rest upon undisturbed sediments.
The PSDM data images crustal structure, the position of the continent/ocean transition and clarifies the dynamics of this obliquely rifted margin. The regional context which can be understood from the data provides better constraints on the distribution of source rocks and reservoir sequences and will lead to new play concepts in the region.
AAPG International Conference and Exhibition, Cape Town, South Africa 2008 © AAPG Search and Discovery