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Abstract: Foraminiferal and Calcareous Nannofossil Biostratigraphy and Well-log Sequence Stratigraphic Analysis of Two Niger Delta Offshore Wells

FADIYA, SUYI LAWRENCE, Obafemi Awolowo University, Ile Ife, Nigeria

Foraminiferal and calcareous nannofossil biostratigrapby and well log sequence stratigraphic analysis were carried out for sequences in two wells from the same oilfield, off-shore the Western. Niger delta.

Two informal planktic foraminiferal zones corresponding to the N17/18 and N19/20 zones of Blow (1969,1979) along with four benthic zones were proposed for both wells. The intervals analyzed for their calcareous nannofossil content fall within the Discoasterquinqueramus NN1ab and Amaurolithustricorniculoitus NN12-NN14 zones of Martini 1971.

A Late Miocene to Early Pliocene age has been assigned to the studied intervals of both wells based on the foraminiferal and calcareous nannofossil assemblages.

A Littoral-Deltaic to Marine (Outer Neritic) environment Of deposition has been inferred for both wells based largely on ft presence of environmentally restricted benthic foraminiferal species.

Three third order Maximum Flooding Surfaces derived from peak foraminiferal abundances and diversities integrated with wireline log signatures enabled the subdivision of the well sections into sequences and Systems Tracts.

Finally all available data showed that the two wells correlate with each other. A correlation of the chronostratigraphic surfaces in the two wells with the global sequence cycle chart of Haq et al, (1987) also shows that the sequences in both wells correspond to geological events ranging in age from about 7.0 Ma to 4.2 Ma.

AAPG Search and Discovery Article #90931©1998 AAPG Foundation Grants-in-Aid