Lithofacies and Environmental Analysis of Reservoir Sandstones in the “ABOM” Oilfield of Eastern Niger Delta, Nigeria

Facies of part of the Coastal swamp depobelt was analyzed using well log. Electrofacies was defined based on well log signatures. The defined facies were inter-related to define a facies association. The facies association were related to deltaic depositional cycles. 10 of such facies association or deltaic cycles were seen in the interval studied. The facies association or deltaic cycles have a different composition of facies related to the level of preservation of the components of the association. The component of the facies association seen include marine clay facies, lower shoreface facies, upper shoreface facies, prograding mouth bar facies and fluvial facies. The marine clay facies underlie each facies association and the channel / prograding mouth bar cap the association where it is preserved. The lower shoreface facies, upper shorefacies, prograding mouth bar and fluvial facies form the Reservoir sandstones. The identified facies association was seen to be repeated in the interval studied though with different composition. This reflects different deltaic depositional cycles with different component of facies due to the prevailing depositional processes occurring at the period of deposition and those affecting the deposit of the cycles after deposition. The arrangements of the different components of the facies within the facies association will help in the prediction of reservoir sand bodies in any deltaic depositional cycle.

LATE MIOCENE CALCAREOUS NANNOFOSSIL STRATIGRAPHY AND BIOEVENTS CORRELATION: KALIDONIA CASE SECTION (NW CRETE, GREECE)

Calcareous nannofossils are widely used for biostratigraphic correlations. Quantitative approaches enable better understanding of reliability of bioevents. In order to refine the late Miocene stratigraphy ofNW Crete, the deposits of Kalidonia basin along its type section are here investigated. It was possible to distinguish the Tortonian/Messinian boundary by NNlla & NNllb, CN9a & CN9b, MNNlla & MNNllb biozones. Reticulofenestra pseudoumbilicus PB (Paracme Beginning) and R. rotaria FO (First Occurrence) proved to act as additional significant biohorizons improving the stratigraphie evolution of the studied paleobasin and providing a tight biochronologic framework. The Kalidonia section fully covers an undisturbed marine depositional cycle from the upper Tortonian to upper Messinian, where a predominant deep water fades (DWF) is followed by transitional sediments (TF) and the sequence closes at the top by a reefal-bioclastic fades (RF) relative to the 'Calcare di Base ' in Italy indicating the 'Messinian Salinity Crisis Event.

Dinoflagellate cyst stratigraphy and palaeoecology of the Pliocene in northern Belgium, southern North Sea Basin

Dinoflagellate cysts and other palynomorphs from the Pliocene Kattendijk and Lillo formations, exposed in two temporary outcrops in northern Belgium, provide new information on the biostratigraphic position and sequence stratigraphic interpretation of these units. Dinoflagellate cysts from the Kattendijk Formation indicate an age between about 5.0 Ma and 4.7–4.4 Ma (early Early Pliocene) in our sections, confirming a correlation with standard sequence 3.4 and implying a slightly greater age than the Ramsholt Member of the Coralline Crag Formation of eastern England. The unconformity at the base of the Kattendijk Formation was not seen, but presumably correlates with sequence boundary Me2 at 5.73 Ma. The overlying Lillo Formation is late Early Pliocene or early Late Pliocene (c. 4.2–2.6 Ma) in age, and the unconformity at its base may be correlated with sequence boundary Za2 at 4.04 Ma or Pia1 at 3.21 Ma. The Oorderen Sands and superjacent Kruisschans Sands members (Lillo Formation) are both part of the same depositional cycle. They were probably deposited before 2.74 Ma, and certainly before the onset of Northern Hemisphere cooling at c. 2.6 Ma. Evidence from dinoflagellate cysts indicates that both a shelly unit at the base of the Lillo Formation and the lower part of the overlying Oorderen Sands were deposited during a conspicuously cool climatic phase, with warmer temperatures returning during later deposition of the Oorderen Sands and Kruisschans Sands members. Many dinoflagellate cyst and acritarch species are reported here for the first time from the southern North Sea Basin. Selenopemphix conspicua (de Verteuil & Norris, 1992) stat. nov. is proposed.