ABSTRACT
One hundred and seventy six (176) Ditch Cutting samples of 15 ft to 10,632 ft from #1 Well Greater Ughelli Depo Belt, Niger Delta Basin were subjected to Sedimentological Analysis. The Sedimentological analysis allowed the erection of twenty nine (29) lithozones of Clayey Sandstone, Sandstone, Sandy Shale, Shale and Shaly Sandstone lithofacies and the identification of minerals which include: Quartz, Iron oxide, Pyrite, Glauconite, Carbonate and Mica. Fifty (50) Shale and Sandy Shale lithofacies were sampled for Standard Palynology and Foraminifera analysis. The Foraminifera analysis resulted in the recovery of Benthonic (Arenaceous and Calcareous) Foraminifera with the absence of Planktonic Foraminifera while the Palynological analysis resulted in the recovery of Miospore (Pollen and Spore), Dinocyst and Ancillary microfossils (Pediastrum, Foraminifera Test Lining and Fungal Spore/Fruit).
The absence of Dinocyst and Foraminifera, abundant diversity and population of Miospore, presence of Iron oxide, Quartz, lithofacies of Sandstone and Clayey Sandstone indicate a Continental - Transitional Environment (15ft – 8,790ft) and this is typical of the Benin Formation. The few to regular occurrences of Dinocyst and Foraminifera, presence of Mica, Glauconite, Pyrite, as well as the alternation of the lithofacies of Shaly Sandstone, Sandy Shale and Shale indicate a Paralic (inner neritic) environment (8,850ft – 10,632ft) and this is typical of the Agbada Formation.
A N2 – N3 Foraminifera zone delineated at 10,530ft – 9,870ft was erected in the well section with the Last Downhole Occurrence (LDO) of Spirosplectamina wrightii and the First Downhole Occurrence of Bolivina imperatrix (FDO). These Foraminifera events suggest an Oligocene age of about 33.0 – 25.0Ma numerical age for the sediments within this interval.
Four (4) palynological zones have been identified in the well section. These are P 540 identified at 10,530ft - 10,290ft using the Base Continuous of Arecipites exilimuratus and the increase in Retibrevitricolporites oboendensis, P 560 defined at 10,290ft – 9,750ft with the increase in Retibrevitricolporites oboendensis and the Quantitative Base of Peregrinipollis nigericus, P 580-P620 defined at 9,750ft – 7515ft with the Quantitative Base of Peregrinipollis nigericus and the Top of Praedapollis africanus and P630 identified at 7,515ft – 6,300ft with the Top of Praedapolis africanus and increase in Praedapollis flexibillis respectively. These palynological events suggest Oligocene – Early Miocene age for the sedimentary succession penetrated by #1 well, which has a numerical age of 33.0 – 21.8 Ma.
The Sequence Stratigraphy interpretation deduced from the integration of the Dinocyst and Foraminifera abundance and diversity peaks as well as the Litholog resulted in the identification of six (6) Maximum Flooding Surfaces at 10,470ft, 10,230ft, 9,510ft 9,150ft, 8910ft, 7275ft of 33Ma, 31.3Ma, 28.1Ma, 26.2Ma, 24.3Ma, 22Ma and five (5) Sequence Boundaries at 10,410ft, 9,570ft, 9,270ft, 8,790ft, 7,215ft dated 32.4Ma, 29.3 Ma, 27.3Ma, 23.7Ma and 21.8Ma.
