Original paper
Source rock evaluation and thermal maturity the Upper Cretaceous rocks in Abu El Gharadig Basin, Egypt: Insights to the petroleum system
Abd El Gawad, Esam A.; Makled, Walid A.; Mousa, Ahmed S.; El Hariri, Tarek Y.; Mousa, Doaa A.; Hamed, Tamer E.
Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen Band 302 Heft 3 (2021), p. 263 - 297
40 references
published: Dec 23, 2021
manuscript accepted: Nov 8, 2021
manuscript received: Sep 12, 2021
ArtNo. ESP155030203001, Price: 29.00 €
Abstract
The Upper Cretaceous rocks of the Abu Roash and Bahariya formations are among of earliest recorded source rocks in the Abu El Gharadig Basin the Western Desert of Egypt. In the present study, samples from three wells have been studied and analyzed by the organic geochemistry and organic petrography to determine the origin of the organic matter and their thermal maturity to evaluate their hydrocarbon generation potentiality. The determined source rocks are placed in a model based on the seismic data to build up a petroleum system. The Bahariya Formation and the members of the Abu Roash Formation are found to contain fair to good quantities of organic matter in Ag‑4 well, and specifically reach to very good in the F Member in Spyglass‑1X and AG121‑X. The organic matter was subjected to microscopic examination using transmitted and reflected white and blue lights. Five palynofacies types were determined by the statistical cluster analysis of organic matter. These palynofacies types are sorted out based on the proximal–distal trend and they include the distal humid dysoxic palynofacies type A, highly proximal arid oxic palynofacies type B, proximal humid oxic palynofacies type C, distal anoxic palynofacies type D and distal humid suboxic palynofacies type E. These palynofacies types contain different type of kerogen in variable amounts. The oil prone kerogen type II that is composed mainly of AOM with distinguishable fluorescence color and inclusions in addition to cuticles and palynomorphs are found to be dominant in the palynofacies distal anoxic palynofacies type D and distal humid suboxic palynofacies type E. Other gas prone kerogen type III and mixed type II/III are found in the other palynofacies type. The pyrolysis analysis by the Rock Eval and gas chromatography confirmed the microscopic results with type II, type III and Mixed II/III, with highest quality organic matter in the Abu Roash F Member. The studied section includes significant levels with oil prone materials. The organic conversions levels remained low despite thermally mature rocks in the Abu Roash G, F, E, D and C members and the Bahariya Formation as indicated by the vitrinite reflectance, fluorescence and Tmax data. The burial history models revealed onset of oil generation between 18 and 22 Ma in the Miocene. An active petroleum system is based on the determined source rocks in the succession of the Abu Roash and Bahariya formations, where the hydrocarbon migrated and accumulated through the fault zones as illustrated by seismic 3D model.
Keywords
Upper Cretaceous • Abu El Gharadig Basin • Abu Roash Formation • Bahariya Formation • source rock evaluation • oil-source correlation