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Seismic stratigraphic analysis for hydrocarbon exploration in the Beta Field, Coastal Swamp Depobelt, Niger Delta

Adeleye Mutiu A., Yekeen Kazeem O., Amidu Sikiru A.

Geology, Geophysics and Environment

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2020

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Vol. 46, no. 4

259--271

EN

Hydrocarbon exploration analysis from a seismic stratigraphic approach was carried out within the Beta Field, Coastal Swamp Depobelt, Niger Delta, to identify system tracts and sequence boundaries that could be associated with potential hydrocarbon accumulation. 3D seismic volume and data from four wells were analyzed. Depositional sequences, system tracts, sequence boundaries, and candidate maximum flooding surfaces were picked from logs, while reflection patterns and terminations were interpreted from seismic sections. Log shapes from gamma rays in combination with seismic facies analysis were interpreted in order to delineate lithology, depositional environments and depositional sequences. Seismic attributes were extracted and were draped on gridded surfaces from the interpreted seismic horizons. These were integrated with structure maps to obtain structural and stratigraphic trends, and possible presence of reservoir sand. Five depositional sequences and nine seismic facies were identified within the field. The depositional sequences were designated Sequences S1 to S5 based on the depth of the occurrences and stacking patterns. This study reveals a progression from fluvial depositional settings to the shelf. The main reservoirs identified are the sand units of the highstand and lowstand within three depositional sequences (S1, S4 and S5) although interbedded sands within the TST of S4 and S5 are also suspected of being potential reservoirs. The channel sand deposits within the study area are suspected to be hydrocarbon bearing as they occurred within the complex fault trapping system popular in the Niger Delta. The application of seismic stratigraphy, as shown in this study, serves to encourage exploration in the Niger Delta where it could be effectively employed for reducing risk in hydrocarbon exploration.

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Well-log based rock physics template of the Vienna Basin and the underlying Calcereous Alps

Tucovic N., Gegenhuber N.

Acta Geophysica

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2017

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Vol. 65, no. 3

441--451

EN

In this study, the ratio of compressional and shear wave velocity versus acoustic impedance as rock physics template for northern part of the Vienna Basin has been derived for siliciclastic rocks based on formation evaluation of well-log data. The results have been verified through wells in different areas drilled in various depths. Additionally, depositional sequences like prograding deltas and braided rivers have been plotted onto the rock physics template to illustrate the effect of changing shale volume. Carbonates below the basin have been included into the study and results from previous projects, based on laboratory data and petrophysical models on certain lithologies in the Vienna Basin, have been used to compare the outcome. The result is a rock physics template which includes important properties such as porosity, true vertical depth and fluid type from log data and which is considered useable throughout different areas and various lithologies of the Vienna Basin.

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The Anisian carbonate ramp system of Central Europe (Peri-Tethys Basin): sequences and reservoir characteristics

Gotz A., Lenhardt N.

Acta Geologica Polonica

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2011

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Vol. 61, no. 1

59-70

EN

During Middle Triassic times, the Peri-Tethys Basin bordered the north-western Tethys shelf and was connected to the open Tethys Ocean via three seaways. Today, Lower Muschelkalk carbonates of this epeiric sea cover large parts of Central Europe, documenting the evolution of a low-relief, homoclinal, mud-dominated ramp system during the Anisian. In view of their geotectonic/climatic setting, depositional processes, facies architecture, and distribution, the rocks are considered as an outcrop analogue for layer-cake reservoirs of world-wide importance, e.g. the Permo-Triassic Khuff or Jurassic Arab carbonates in the Middle East. In general, two different reservoir types and their interplay might be considered: The proximal stacks of muddy dolostones (NW part of the basin) and the more distally developed grainy limestones (central and SE part of the basin). The rather uncommon depositional setting with minor relief and minimal accommodation contributed to both, the stratal and lateral facies development, and to unusual and possibly even "inverted" facies patterns with thick, grainy facies found in the more distal environments. Based on litho- and microfacies analyses, six main facies types are distinguished, building characteristic cyclic facies successions of different hierarchies. The stratal architecture of small-scale depositional sequ ences systematically changes in relation to their relative proximal-distal position on the Muschelkalk ramp system. Here, we present porosity and permeability data of the different facies types and within the basin-wide sequence stratigraphic framework. Dolo-wacke-/packstones and peloid grainstones attain the highest porosities of up to 24%, whereas bioclastic grainstones show porosities of up to 8%. The platy and nodular mud-/wackestone and most of the bioclastic wacke-/packstones typically show porosities below 2%. Even in the most porous strata, permeabilities do not exceed 10 mD, and only a few carbonates show higher permeabilities up to 90 mD. Within large-scale, third-order depositional sequences late highstand deposits represent the most permeable sediments.

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Sedymentacja utworów miocenu we wschodniej części zapadliska przedkarpackiego

Dziadzio P., Maksym A., Olszewska B.

Przegląd Geologiczny

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2006

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Vol. 54, nr 5

413-420

EN

Results of new biostratigraphical investigations correlated with nannoplankton zones permit to suggest that deposits which are filling the eastern, Polish part of the Carpathian Foredeep Basin include also the late Sarmatian and Panonian deposits. The filling of eastern parts of the Carpathian Foredeep, as in most foredeep basins, took place in two main stages; (1) underfilled flysch stage - lasting from the early Badenian to the lower part of late Badenian (Moravian– Wieliczian) and (2) overfilled molasse stage — lasting from upper part of the late Badenian to Panonian (Kosovian–Meotian). Classically, this flysch to molasse transition is interpreted as a record of the migration of the thrust wedge and foreland basin over the hinge line of the inherited passive margin. Also, the Badenian and Sarmatian successions are characterised by very diverse facies, which were deposited in various depositional environments. A detailed sedimentological analysis of cores, together with well log analysis, and seismic sections permitted to fit the stratigraphic column into a sequence stratigraphic framework. Within this framework, the Badenian and Sarmatian successions are interpreted to have been deposited within 3 third-order depositional sequences: the first two in the Badenian (not recognised in seismic scale), and the third during the Sarmatian, which consists of 4 fourth-order sequences (Dziadzio, 1999, 2000), with total thickness of 800 to over 3000 m. The M3 boundary is interpreted as a flooding surface within the fourth order, oldest Sarmatian depositional sequence. The M2 boundary corresponds to the boundary between two foraminiferal zones Anomalinoides dividens and Varidentella reussi, within the Sarmatian succession, which lies in the upper part of the second Sarmatian sequences, near the maximum flooding surface, in late phase of highstand sea level. The M1 boundary is interpreted as a transgressive surface within the third Sarmatian sequence. The boundary M0 marks transgressive surface within the fourth Sarmatian sequence and also is a stratigraphical boundary between two youngest foraminiferal zones Velapertina reussi and Porosononion granosum, and marks a border between the Wolhynian and Bessarabian stages.