Palynology and Geochemistry of GPTSW-7 Well, North Western Desert, Egypt
Haytham S. El Atfy1, Salah Y. El Beialy2, Martin J. Head1, Essam M. El Khoriby1, and Ramadan H. Abu Zeid1
1Geology Department, Faculty of Science, Mansoura University, Mansoura, Egypt
2Department of Earth Sciences, Brock University, St. Catharines, ON L2S 3A1, ON, Canada
The present study of the Bahariya and Abu Roash formations in well GPTSW-7 refines our understanding of the subsurface Cretaceous of the north Western Desert of Egypt. Our investigations are based on the palynological analyses of 71 ditch cutting samples, of which 24 have also been analysed for geochemistry.
Five palynological zones ranging in age from early Cenomanian to late Turonian or Coniacian are proposed, based on quantitative and qualitative changes in the palynomorph assemblages. Palynofacies analyses indicate that the Bahariya and Abu Roash formations are primarily of kerogen III type and hence gas prone. However, the Abu Roash "F" Member contains a high proportion of amorphous organic matter (AOM) and a well-known organic carbon-rich black shale horizon considered to represent the terminal-Cenomanian global oceanic anoxic event (OAE2) known as the Bonarelli Event.
Total organic carbon (TOC) and Rock-Eval pyrolysis show that the Bahariya Formation and the Abu Roash “G” Member are gas prone (type III kerogen).The Abu Roash “E”, “D”, “C” and “A” members may also be gas prone (type III kerogen) and appear to contain highly oxidized terrestrial organic matter. In contrast, the Abu Roash “F” Member has very high TOC and HI values indicating a highly oil prone facies. While this finding is not unexpected for an anoxic black shale, it contrasts with earlier studies (Schlumberger, 1995) that suggest a gas prone nature.
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