New Insights into the Formation of Mesozoic Depocenters in North Africa and Its Influence on Differential Enrichment in Hydrocarbon

doi:10.19657/j.geoscience.1000-8527.2022.054

Abstract

Abstract:

The North Africa area is extremely rich in hydrocarbon resources. However, the hydrocarbon is also distributed with inhomogeneity within this area. The previous investigations payed less attention to this characteristic of differential enrichment in hydrocarbon. This study mainly focuses on this issue in aspects of the evolution and formation mechanism of Mesozoic basin depocenter. Comprehensive re-analysis on basic geology and hydrocarbon exploration data is implemented. The results indicate that, on the northern margin of Gondwana continent in North Africa, there are three Mesozoic depocenters that exist in isolation from each other, such as Oued Mya-Pelagain, Sirt, Eastern Mediterranean. These three Mesozoic depocenters are located on the three preexisting NE-trending palaeohighs formed during the Hercynian orogeny, Allala, Sirt and Lewant palaeohighs respectively; they have a formation mechanism characterized by “negative inversion and collapse of palaeohigh”. Mesozoic depocenters are also close to the edge of the Neotethys Ocean, indicating that their formations are controlled by preexisting NE-trending Hercynian palaeohighs together with the opening of the Neotethys Ocean. Due to the following favorable factors the areas in or adjacent these Mesozoic depocenters became the most important hydrocarbon enrichment zone: structures related to Hercynian orogeny, sandstone reservoir with good quality produced by erosion on Hercynian palaeohighs, and excellent Mesozoic source rock. Thus the formation process of the Mesozoic basin is one of the most significant factors controlling the differential enrichment in hydrocarbon in the North Africa.

Key words: Tethyan tectonic domain, North Africa, Hercynian orogeny, structural inversion, differential enrichment in hydrocarbon

CLC Number:

HUANG Lei, ZHANG Zhongmin, ZHAO Xiaochen, LÜ Xueyan, WANG Aiguo, LIU Chiyang, SONG Shijun, YIN Ke, LI Xin, LIU Jingjing. New Insights into the Formation of Mesozoic Depocenters in North Africa and Its Influence on Differential Enrichment in Hydrocarbon[J]. Geoscience, 2022, 36(05): 1218-1229.

Figures/Tables 12

Fig.1 Distribution of basins and discovered hydrocarbon in North Africa(data of oil and gas fields after ref. [1])

Fig.2 Chronostratigraphy of the Phanerozoic of the main North African basins (modified from ref.[11])

Fig.3 Paleogeological maps of Northern Gondwana during Silurian and Late Triassic(modified from ref.[12])

Fig.4 Characteristics of geological structure under the Hercynian tectonic interface in the North Africa and Middle East((a), modified from refs.[10,19]) and generalized structural cross-section across the North Africa ((b), seeing Fig.1 for the location)

Fig.5 Depth of Hercynian unconformity and distribution of regional depocenters (modified from ref. [10])

Fig.6 Geological cross-section across the Oued Mya Basin, and sections flattened on the top of the Hercynian unconformity and the top of the Triassic (seeing Fig.4(b) for the location, the present-day section after Tellus database)

Fig.7 Tectonic evolution section across the south portion of the Pelagain Basin

Fig.8 Geological cross-section across the Sirt Basin ((a) present section;(b)section flattened on the top of the Paleozoic;after ref. [26])

Fig.9 Herynian unconformity subcrop in the Eastern Mediterranean (a), well correlation across the south margin of the Palmyride basin (b) and well correlation cross-section across the Palmyride basin, flattened on the Hercynian unconformity (c) (modified from ref.[36])

Fig.10 Conceptual models for formations of Mesozoic rift basin in North Africa and Middle East

Fig.11 Distribution of main Paleozoic and Mesozoic source rock in North Africa (modified from refs. [2,40⇓⇓⇓-44])

Fig.12 Paleozoic reservoir profile across the East Sirt Basin (after ref. [33])

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