Aspects of palyno-organic facies analysis: Comprehensive evaluation of the source rocks and age of some subsurface Lower Cretaceous core materials in the north Western Desert, Egypt

The Qasr oil and gas Field is located in the north western desert of Egypt. It belongs to the southeastern part of the Lower Jurassic-Cretaceous Shushan Basin. The Lower Cretaceous Alam-El Bueib formation composed of clastic rocks with noticeable carbonate proportions, and forms multiple oil-bearing sandstone reservoirs in Qasr field. The study aims to define and analyze the Surface and subsurface structural features which are a key issue in assessing reservoir quality. Through this integrated approach, one may be able to identify lithologies and fluids in this region and provide possibly new hydrocarbon fairways for exploration. For this purpose, seismic and well data were interpreted and mapped in order to visualize the subsurface structure of the Cretaceous section. Results show the effect of NE-SW, NW-SE, and E-W trending normal faulting on the Lower Cretaceous Alam-El Bueib formation and is extended to the Upper Cretaceous Abu Roash Formation. The effect of folding is minimal but can be detected. These normal faults are related to the extensional tectonics which affected the north western desert of Egypt during the Mesozoic. One reverse fault is detected in the eastern part and is related mostly to the inversion tectonics in the Late Mesozoic. The depth structure contour maps of the Alam-El Bueib horizons (AEB-1, AEB-3A, and AEB-3D) show several major normal faults trending NE-SW and minor normal faults trending NW-SE. One larger branching normal fault trending E-W and lies to the south of the study area. These step-normal faults divide the area into a number of tilted structural blocks which are shallower in the south and deepen to the north. The area of study was most probably affected by E-W trending normal faults during the opening of the Atlantic Ocean in the Jurassic. Later right-lateral compression resulted from the movement of Laurasia against North Africa, changed their trend into NE-SW faults with minor NW-SE trending folds. These compressive stresses are also responsible for the reverse faulting resulted by inversion in the Late Mesozoic.

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Palynostratigraphy and paleoecology of a Lower Cretaceous (upper Barremian–lower Aptian) succession in the Shushan Basin, northwestern Egypt: inferences on intra- and inter-basinal correlations

Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen ◽

10.1127/njgpa/2019/0855 ◽

2019 ◽

Vol 294 (2) ◽

pp. 177-195 ◽

Cited By ~ 2

Author(s):

Tarek F. Mostafa ◽

Amr S. Deaf ◽

Maher I. El Soughier ◽

Walid A. Makled

Keyword(s):

Source Rock ◽

Lower Cretaceous ◽

Relative Difference ◽

Hydrocarbon Exploration ◽

Western Desert ◽

The North ◽

Depositional Settings ◽

Assemblage Zone ◽

Local Tectonics ◽

North Western

Recent national and international demand for additional resources of the fossil fuel resulted in extensive hydrocarbon exploration activities in Egypt to further explore possible petroliferous rock units that were conventionally deemed as barren or having non- commercial reserves such as the Alam El Bueib Formation. This increased the stress to enrich the lithological correlation of this formation across the north Western Desert to better understand its regional lithological characteristics and thus its potential regional reservoir/source rock quality. Palynostratigraphic analysis of Lower Cretaceous successions in the Tut-1X and Amoun-1X wells in the Shushan Basin, north Western Desert enabled the recognition of the upper Alam El Bueib Formation in both wells, in contrast to a previous study, which suggested non-deposition of this formation in the Amoun-1X well. This highlights the important role of the palynology as a key stratigraphic tool, which helped effectively in recognising this problematic monotone clastic formation, where other marine microfossils are lacking. This also shows that recognition of this formation based on lithological criteria only was impractical and misleading. Marker terrestrial and marine palynomorph taxa recovered from the upper Alam El Bueib Formation enabled dating it as late Barremian– early Aptian and were used to identify two palynological biozones that can be traced out regionally across the Shushan, Matruh, and other nearby basins. These biozones are the early Aptian Murospora florida – Afropollis operculatus – Pseudoceratium securigerum Assemblage Zone and the late Barremian Stellatopollis barghoornii – Pseudoceratium anaphrissum– Cyclonephelium vannophorum Assemblage Zone. An undifferentiated interval was recorded just below the upper Barremian strata in the Tut-1X well due to very low palynomorph recovery and absence of marker forms. Composition of terrestrial and marine palynomorph assemblages suggests the upper Alam El Bueib Formation was deposited in fluviodeltaic to proximal inner shelf settings. The Alam El Bueib Formation shows notable regional variations in thickness and considerable lateral and verti- cal changes in lithology due to local tectonics and relative difference in its depositional settings in the Shushan and Matruh basins. Regionally, the Alam El Bueib Formation shows dual reservoir/source rock characteristics, where thick and poorly fossiliferous sandstone units act as reservoir rocks, while moderately fossiliferous finer clastics and carbonates already acted as intraformational source rock intervals in some parts of the Shushan and Matruh basins.

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Geodynamics and Oil and Gas Potential of the Yenisei-Khatanga Basin (Polar Siberia)

Minerals ◽

10.3390/min8110510 ◽

2018 ◽

Vol 8 (11) ◽

pp. 510 ◽

Cited By ~ 5

Author(s):

Valery Vernikovsky ◽

Georgy Shemin ◽

Evgeny Deev ◽

Dmitry Metelkin ◽

Nikolay Matushkin ◽

...

Keyword(s):

Lower Cretaceous ◽

Oil And Gas ◽

Foreland Basin ◽

Gas Reservoirs ◽

The North ◽

Western Arctic ◽

Folded Structures ◽

Gas Potential ◽

First Time ◽

North Western

The geodynamic development of the north–western (Arctic) margin of the Siberian craton is comprehensively analyzed for the first time based on our database as well as on the analysis of published material, from Precambrian-Paleozoic and Mesozoic folded structures to the formation of the Mesozoic-Cenozoic Yenisei-Khatanga sedimentary basin. We identify the main stages of the region’s tectonic evolution related to collision and accretion processes, mainly subduction and rifting. It is demonstrated that the prototype of the Yenisei-Khatanga basin was a wide late Paleozoic foreland basin that extended from Southern Taimyr to the Tunguska syneclise and deepened towards Taimyr. The formation of the Yenisei-Khatanga basin, as well as of the West-Siberian basin, was due to continental rifting in the Permian-Triassic. The study describes the main oil and gas generating deposits of the basin, which are mainly Jurassic and Lower Cretaceous mudstones. It is shown that the Lower Cretaceous deposits contain 90% of known hydrocarbon reserves. These are mostly stacked reservoirs with gas, gas condensate and condensate with rims. The study also presents data on oil and gas reservoirs, plays and seals in the Triassic, Jurassic and Cretaceous complexes.

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