Biostratigraphy, Depositional Environment and Sequence Stratigraphy of Akata Field (Akata 2, 4, 6 and 7 Wells), Eastern Niger Delta, Nigeria.

Abstract

Foraminiferal biostratigraphy and sequence stratigraphic analysis were carried out in the Akata Field from Akata-2, Akata-4, Akata-6 and Akata-7 wells in the eastern Niger Delta. Three planktic foraminiferal zones Globorotalia continuosa, Globorotalia obesa/Globorotalia mayeri, and Globorotalia peripheroacuta together with three benthic zones of Spirosigmoilina oligocaenica, Uvigerina sparsicostata, and Eponides eshira/Brizalina mandorovensis were established in both Akata-2 and Akata-4 wells. One planktic foraminiferal zone of Praeorbulina glomerosa was proposed for Akata-6 and Akata-7 wells. One benthic zone of Brizalina mandorovensis/Eponides eshira and Poritextularia panamensis are proposed for Akata-6 and Akata-7 wells respectively. Calcareous nannofossil analysis was also carried out in Akata-6 and Akata-7 wells, Sphenolithus heteromorphus Zone was established in both wells. Miocene age has been assigned to the studied intervals of the four wells based on the foraminiferal assemblages. The studied wells were correlated using the established biostratigraphic zones. A littoral (deltaic) to marine (outer neritic) environments of deposition has been inferred for the four wells based largely on the presence of environmentally restricted benthic foraminifera species. Three third order maximum flooding surfaces were recognized in Akata-2 and 4 while two were recognized in Akata-6 and 7 wells. The wells have been divided into sequences and systems tracts.