Sequence Stratigraphic Analysis of Well BB-3, Deep Offshore, Niger Delta Basin, Nigeria: Insight from Palynological Studies

Abstract

Abstract Sequence stratigraphic analysis was carried out on well BB-3, deep offshore, Niger Delta Basin, Nigeria. This is done in order to delineate sequence stratigraphic surfaces using vertical sequence of depositional environment. Palynological analysis was carried out on 82 ditch cutting samples from well BB-3 using the standard acid technique in order to zone the well. Open hole geophysical log data was also provided for the studied interval 10700–15600 ft 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 three taxon range biozones in BB-3 well, the proposed palynological biozones are Belskipollis elegans, Crassoretitriletes vanraadshooveni, Pachydermites diederixi biozones which are correlatable with the pantropical zones. Samples from the section are dated early Miocene to middle Miocene age based on the independent palynological evidences. The deduced paleoenvironments of the strata penetrated by the well range from outer neritic through bathyal to abyssal. The successions were broken into Highstand Systems Tracts (HST), Lowstand Systems Tracts (LST) and Transgressive Systems Tracts (TST) and chronostratigraphic surfaces such as Maximum Flooding Surface (MFS), Sequence Boundary (SB) and Transgressive Surface (TS). Three HST, three LST, three TST, two MFS and three SB were recognised. The MFS and SB were dated 15.9 Ma, 15.0 Ma and 16.7 Ma, 15.5 Ma, 13.1 Ma respectively by correlation of the established pollen zones with the Niger delta Cenozoic chronostratigraphic chart. The sandstone and shale units of the Systems Tracts are potential hydrocarbon reservoirs and seal rocks respectively.