Recognition of Blow Foraminifera Zones in the Tertiary Sediments in F- Well, Niger Delta

F.A Lucas,O.E Ononeme

doi:10.4314/jasem.v23i12.23

Abstract

Foraminiferal Micropaleontology of Tertiary sediment in F-Well Niger Delta Basin were carried out using foraminiferal biostratigraphy as geologic tools. Sedimentological description was carried out on 679 ditch cutting samples which aided the erection of 103 lithozones. Fifty (50) ditch cutting samples was used with the aim of establishing the Foraminiferal Biozones and age of the well. A total of eighty (80) foraminiferal species were recorded, most of the species recorded are calcareous and arenaceous benthic foraminiferal species. They were about twenty-eight (28) diagnostic foraminifera recognized. The evaluation of these foraminifera species enabled us to recognize the zones. The foraminiferal abundances revealed two bio zones N4-N3 Planktic zone and N3 – N2 Planktic zone which were suggested based on index species among the recovered foraminiferal assemblages. N4-N3 Planktic zone has a reference interval of 8,000ft – 9,400ft. The top of this zonal interval which ought to be marked by the FDO of Ammonia becarril was absent but was estimated to be 8,000ft. The base of this zonal interval is marked by the LDO of Epistominella vitriea at 9,400ft. Planktic zone N3 – N2 has a reference interval of 9,400ft – 10,000ft. The top of this interval is marked by the FDO of Bolivina imperatrix at 9,400 ft. The base of this interval is marked by the LDO of Spirosplectamina wrightii at 10,000 ft. The studied intervals in the wells are dated Early Miocene - Oligoocene. Using the lithologic and foraminiferal studies, it is inferred that the intervals penetrated by the well correspond to Agbada Formation.Keywords: Foraminifera, First Downhole Occurrence, Last Downhole Occurrence, Oligocene.

Highlights

The study area lies within the Niger Delta Basin, which is situated on the continental margin of the Gulf of Guinea in equatorial West Africa Klett et al 1997
Biostratigraphy is defined as “the classification of sediment units according to observable variations in fossil content” Lowe JJ and Walker MJC. 1997, enables sediment sequence to be divided into biostratigraphic units or biozones, each characterised by a distinctive fossil assemblage
Deep-water agglutinated foraminifera have been used during hydrocarbon explorations since the 1970’s when the first Deep Sea Drilling Programme (DSDP) established their value for both biostratigraphical and palaeoenvironmental studies Gradstein FM and Berggren WA 1981

Summary

Introduction

The study area lies within the Niger Delta Basin, which is situated on the continental margin of the Gulf of Guinea in equatorial West Africa Klett et al 1997. 1997, enables sediment sequence to be divided into biostratigraphic units or biozones, each characterised by a distinctive fossil assemblage. Planktonic foraminifera are good stratigraphic indicators of the interval covering the Jurassic to present, while benthic foraminifera are found since the Cambrian (Ordovician to Present for calcareous species). The use of foraminiferal analysis in this study enables us to determine biostratigraphic zonation of the sediments penetrated by the drill.

Results

Conclusion