Browsing by Author "Nwadike, Cynthia Benedicta Nkeiruka"

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    Sequence stratigraphic interpretation of sediments in Meren field offshore Niger Delta using wireline log patterns and biostratigraphic data
    (Federal University of Technology, Owerri, 2025-03) Nwadike, Cynthia Benedicta Nkeiruka
    Well logs and biostratigraphic data were employed in the reconstruction of sequence stratigraphic framework for Meren 01 and 02 Wells in the Meren Field offshore Niger Delta. A total of one hundred and sixty four (164) core samples were examined for microfossils using standard procedures for foraminifera and palynomorphs analysis. The Palynological Zones (P-Zones) and age determination was achieved using First Downhole Occurrence (FDO), Downhole Increase or Decrease, Quantitative Base (QB), Last Downhole Occurrence (LDO) or Base Occurrence (BO), Top Regular (TR) or Quantitative Top Occurrences (QTO) of age diagnostic palynomorphs as well as known marker species. Additionally, the samples were subjected to detailed description based on their respective lithology. The GR log pattern and microfossil abundance and diversity were used to delineate the sequences to different kinds of system tracts. Accordingly, four depositional sequences were identified comprising of five Sequence Boundaries (SB) dated at 6.30Ma, 5.5 Ma, 3.8 Ma, 3.0 Ma and 2.6 Ma, six Maximum Flooding Surfaces (MFS) dated at 7.00 Ma, 5.80 Ma, 5.00Ma, 3.40 Ma, 2.70 Ma and 2.45 Ma of Middle – Late Miocene age were recognized when significant foraminiferal signatures obtained were integrated with that of palynology. The key stratigraphic surfaces which were identified using index microfossils and higher GR count can be used for basin wide correlation. From the correlation chart, the Maximum Flooding Surfaces are associated with diversity of microfossils and high concentration of radioactive minerals that gave rise to high GR reading at this surface unlike the Sequence Boundary where fewer or no microfossils were identified with low GR readings. The dated stratigraphic surfaces corroborated with established shifts landward and basin ward according to established schemes. Giving the available data from biostratigraphy and GR log, the environment of deposition was inferred to trend from coastal deltaic to marine. The environments over which sediments of Meren-01 and 02 were deposited have been investigated through the integration of sedimentological, palynological and micropaleontological characteristics of these sediments. Based on bathymetric profiles, the shales within the study area are open marine, shelf and floodplain fines, while the sand sequences are most likely due to lobe switching of the river channel and deposition of interdistributary bay. Three reservoirs R4000, R6000 and R8000 were also identified and correlated across the wells. Given their rich sand development, the quality of these reservoirs is generally good and they all possess excellent net-to-gross. Additionally, their facies distribution shows that non reservoir units (shale and silt facies) are in minor amounts.