Hydrocarbon Potential of the Lamu Basin of South-East Kenya
K. Nyagah, J. J. Cloeter, A. Maende, D. G. Mburu, J. T.
Schulenberg, F. Otts, S. W. Karanja, and C. Sewe
The Lamu basin occupies the coastal onshore and offshore areas of south-east
Kenya. This fault bounded basin formed as a result of the Paleozoic-early
Mesozoic phase of rifting that developed at the onset of Gondwana dismemberment.
The resultant graben was filled by Karroo (Permian-Early Jurassic) continental
siliciclastic sediments. Carbonate deposits associated with the Tethyan sea
invasion, dominate the Middle to Late Jurassic basin fill. Cessation of the
relative motion between Madagascar and Africa in the Early Cretaceous, heralded
passive margin development and deltaic
sediment progradation until the Paleogene.
Shallow seas transgressed the basin in the Miocene when another carbonate regime
prevailed.
The basin depositional history is characterized by pulses of transgressive and regressive cycles, bounded by tectonically enhanced unconformities dividing the total sedimentary succession into discrete megasequences. Source rock strata occur within Megasequence III (Paleogene) depositional cycle and were lowered into the oil window in Miocene time, when the coastal parts of the basin experienced the greatest amount of subsidence.
The tectono-eustatic pulses of the Tertiary brought about source and
reservoir strata into a spatial relationship in which hydrocarbons could be
entrapped. A basement high on the continental shelf has potential for Karroo
sandstone and Jurassic limestone reservoirs
. Halokinesis of Middle Jurassic salt
in Miocene time provides additional prospects in the offshore area. Paleogene
deltaic
sands occur in rotated listric fault blocks. A Miocene reef play
coincides with an Eocene source rock kitchen.
AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California