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Offshore Lamu Basin, Kenya: Comparison with Northwest Shelf Australia

Matthew Arthur Battrick, Exploration Manager, Pancontinental Oil & Gas NL, Ground Floor, 288 Stirling Street, Perth 6000 Australia, phone: +61 8 9227 3294, fax: +61 8 9227 3211, [email protected]

The Lamu Basin covers a large area of coastal Kenya, extending offshore from a relatively narrow onshore graben to cover most of the continental shelf and slope off Kenya. The hydrocarbon resource potential of the offshore segment of the Lamu Basin can be assessed by comparing with other Gondwana basins on the margins of the Indian Ocean. The Gondwana break-up history of East Africa is reviewed to identify major reservoir-seal pairs and potential source intervals within the basin. The stratigraphy of the offshore Lamu Basin is compared with that of the Carnarvon Basin along Australia's North West Shelf to identify analogue plays and potential resource volumes. Historical well results and recent 2D seismic data have been interpreted to identify various structural styles and play fairway segments.

Four ‘mega-sequences' from the Karroo to the Late Tertiary are identified and all have potential reservoir-seal pairs. Major similarities and some differences in structural styles can be seen between the offshore Lamu and Carnarvon Basins. Yet the Carnarvon Basin has discovered reserves in excess of three billion barrels of oil equivalent and 50 wells per 25,000 square kilometres of productive basin area. Scant, offshore, well control of only one well per 25,000 square kilometres in the Offshore Lamu Basin shows evidence exists of at least two active petroleum systems. The results of the comparison indicate a significant potential resource in a number of trap types, within a core area of the offshore play fairway in the Lamu Basin.

Offshore Lamu Basin, Kenya: Deepwater Fold Belt

Jonathan J. Hull, Woodside Energy Ltd, Perth, WA, 6000, Bahrain, [email protected] and Geoff Freer, Oilsearch, Perth, WA, 6000, Australia.

The Northern Lamu Basin, offshore Kenya, contains a large, untested, passive margin deepwater fold belt with a thick Cretaceous and Tertiary sedimentary section. Large, structural closures related to compressional toe-thrusts are identified over an area of over 7000sqkm.

The Early Cretaceous Anza Graben provided corse clastic sediments into the offshore Lamu Basin through to present day. Rapid sediment loading resulted in extension on the shelf with linked, thin-skinned compression in the basin. The fold belt initiated in the Late Cretaceous and continued through to the Early-Mid Tertiary. With pre- and syn-kinematic, deep-marine reservoir intervals identified in wells and on seismic data and limited trap reactivation since the modelled onset of hydrocarbon generation and migration, the key uncertainty is the presence of an oil-prone source rock .

Previous wells in Kenya have focussed primarily on onshore and shelfal targets with some indications of an active petroleum system, however, none have definitively tested the deepwater petroleum system. To date the only deepwater well (920m water depth) was drilled south of the Davy-Walu high, in a separate basin to the northern Lamu Basin.

The Woodside-led joint venture aims to drill the first ultra-deepwater well offshore East Africa, and the first offshore well in Kenya for 20 years.

Exploration Potential of Africa and Its Margins
2006 AAPG International Conference and Exhibition, (November 5-8, 2006) Technical Program