Calcareous Nannoplankton Analysis of Well BL-2, Deepwater Offshore, Niger Delta Basin

Abstract

Sequence Stratigraphy and biostratigraphy are recent tools that are being developed and incorporated together for the understanding of stratigraphic distribution and prediction of source, reservoir and seal rocks. These tools were used to analyze well BL-2, within the depth intervals of 6000ft - 8880ft offshore, Niger Delta. Calcareous Nannoplankton assemblages encountered in the study were used in determining the biozone and age of the samples of the penetrated well. Intercalation of sand and shale lithologies obtained from the well logs suggests the well BL-2 penetrated the Agbada Formation. Three nannozones were determined - NN10, NN11 and NN12, two sequence boundaries and three maximum flooding surfaces with ages and 5.0Ma, 5.8Ma, 7.0Ma respectively were delineated and used to divide the stratigraphic succession into depositional sequences and their corresponding system tracts. Highstand and Transgressive system tracts were identified in each of the three depositional sequences. However the absence of lowstand system tract can be inferred to have resulted from erosion by succeeding transgressive system tracts. The alternation of highstand and transgressive system tracts is inferred to provide the desired combination of reservoir and source rock required for hydrocarbon generation. The unit's age is Late Miocene to Early Pliocene.