DEPOSITIONAL SEQUENCES IN THE OFFSHORE WABI FIELD IN THE NIGER DELTA NIGERIA
Journal: Earth Sciences Pakistan (ESP)
Author: Amakiri, S., Uko, E. D., Tamunobereton-ari, I., Amakiri, A.R.C., Amonieah, J.
This is an open access article distributed under the Creative Commons Attribution License CC BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited
Well-log, biostratigraphic, chronological chart and seismic data from offshore Wabi Field in the Niger Delta were used to delineate depositional sequences, stratigraphy, systems tracts and flooding surfaces. Geologic faults, horizons systems tracts were detected in seismic section. The faulting patterns ware boundary, synthetic, antithetic, and roll-over faults in N-W to S-E trending. Hydrocarbons are encountered between 9,560 and 12,750ftss in 3-stacked B, O, and R1 reservoirs in crestally collapsed rollover anticlines, which are predominantly shore face. Reservoir R1 was the thickest (320ft) sand unit; Reservoir B was the thinnest (50ft) sand unit. The thinning of the sand sequences at greater depths is indicative of bulk density being increased as the sediment compacted. Sequence Stratigraphic Analysis reveals Onlap is generally associated with marine transgression; Toplap which terminates below the surface, lap out in the landward direction. Three (3) maximum flooding surfaces (MFS) of 20.4Ma, 16.7Ma and 15.9Ma were inferred. The field was deposited during lower to upper Miocene Epoch using the Niger Delta Cenozoic Geologic Data. The reservoirs of interest fall within the following system tracts: B Sand is a Low Stand System Tract (LST), O Sand is a High Stand System Tract (HST) and R1 Sand is a Transgressive System Tract (TST). Two types of facies of channel (blocky signatures) and shoreface (coarsening upward) sand deposits with traces of heterolithic sand, silty sand (serrated motif) and marine shale are inferred. Wabi field is dominantly fluvial (channel deposits) environment as shown by the major blocky log signature. The results could help identify depositional sequences, systems tracts on seismic sections by interpreting the location of their boundaries and flooding surfaces. Moreover, delineation of subsurface structures, reservoir quality and lateral extents are of key importance in the determination of economic viability of Fields and exploration opportunities.