Integrated Biostratigraphic Analysis for Part of Deep Offshore, Niger Delta Basin, Nigeria.

Abstract

Integrated biostratigraphic analysis were carried out on Bobo-3, Doro-1 and Bolia-1X wells deep offshore Niger Delta Basin, Nigeria. Palynological analysis was carried out on 295 ditch cutting samples (Bobo 3 = 82, Doro 1= 109, and Bolia 1X= 104). Foraminiferal and openhole geophysical log data were also provided for the studied interval. The intervals studied are 10700-15600 ft, 8060-16860 ft and 7900-13000 ft in Bobo-3, Doro-1 and Bolia-1X wells respectively belonging to the Agbada Formation. Lithologically, the section varies from alternation of sand and shale units with carbonaceous debris, mica flakes, ferruginised materials and glauconite at some interval as accessory minerals. Biozonation included twelve palynological biozones ( three taxon range biozones in Bobo-3 well, two interval, three taxon range, one non-diagnostic biozones in Doro-1 well and one interval, one diagnostic, three taxon range biozones in Bolia-1X well) and six planktonic foraminiferal biozones ( one taxon range biozone in Bobo-3, one interval, four taxon range biozones in Doro-1 and Bolia-1X wells). The proposed palynological biozones are Stereisporites sp. - Cyperaceaepollis sp., Nymphaepollis clarus- Gemmamonocolpites sp., Multiareolites formosus - Retibrevitricolporites obodoensis, Belskipollis elegans, Crassoretitriletes vanraadshooveni, Pachydermites diederixi and Magnastriatites howardi biozones which are correlatable with the pantropical zones. While established foraminiferal zones are Globorotalia fohsi peripherronda, Globigerinoides extremus-Globigerinoides humerosa, Globorotalia acostaensis acostaensis, Globorotalia fohsi peripherronda and Catapsydrax stainforthi. Samples from the section are dated early Miocene to early Pliocene age based on the independent paleontological evidences. The deduced paleoenvironments of the strata penetrated by the well range from outer neritic through bathyal to deep marine.