Calcareous Nannofossil, foraminifera Biostratigraphy and Paleoenviroonmental analysis of D1 Well, Offshore Eastern Niger Delta, Nigeria

Abstract

Calcareous nannofossils and foraminifera biostratigraphic analyses was carried out on 100 ditch cutting samples from the D1 well, offshore Niger Delta basin. The studied interval ranges from 3440 – 9950 feet. The samples were studied for their litholgy, calcareous nannofossils and foraminferal content with the aim of subdividing the sequaence into foraminifera and calcareous nannofossils bizobes, determining the age and the Paleoenvironment of the strata penetrated by the well. The standard foraminifera and calcareous nannofossils revovery techniques were employed. The lithology of the penetrated sequence is characterised by the alternating sand and shale sequence of the Agbada formation at the lower section, while the predominantly sandy upper section of the well corresponds to the benin formation. Richly diverse calcareous nannofossils and foraminifera assemblages wre recovered. Four foraminifera biozones established in this study are: the Globorotalia tumida/ Valvulina, f/exilis zone , Neogloboquadrlna dutertrel/Cyclammina minima zone, Sphaeroidinel/a de hiscens~Ha~lophragmoides narivaensis zone, Globorotalia merotumida/p/es1otum1da!Ammobaculites agg/utinans zone. Two calcareous nannofossils zones established in this study are the Discoasterspp. and Discoasterquinqueramus/Discoaster berggrenil zones. The age assigned to the studied interval of D1 well ranged from Late Miocene to Early Pliocene based on the recovered assemblages. Outer neritic to Upper bathyal depositional environment is inferred for the entire studied interval of D 1 well because of the frequent occurrence of the diagnostic species of the following genera: Uvigerina, Globocassidulina, Eponides, Bulimina, Pu/lenia, Oridosalis, Sphaeroidina, Cibicidoides, Gyroidinoides and deep water arenaceous forms such as Cyclammina, Kareriella and Recurvoides.