Sedimentology, Structure and Depositional Environments of the Subsurface Cretaceous, North Sinai, Egypt Using Well Logs

Fouad Shaaban,Adam El-Shahat,Mostafa El-Belqasi,Amani Bourselli

doi:10.4236/ijg.2020.113004

Abstract

A complete set of well logs was used to study the sedimentology, structural and depositional environments of the subsurface Cretaceous rocks of northern Sinai, as a promising hydrocarbon province in Egypt. The sedimentological interpretations of well logs show sedimentary sequence of the Early Cretaceous, represented by the Neocomian, Aptian and Albian, which is composed mainly of shales and marls with minor carbonate and sandstone intercalations. Based on the Th/K ratios, the argillaceous sediments are composed of illite, montmorillonite and micas with little amounts of glauconite and chlorite. The environmental interpretations revealed sedimentological environments vary from estuarine to lagoonal and backreef of the Barremian-Aptian rocks, and from continental to estuarine in the Aptian-Albian. By contrast, the Late Cretaceous rocks, represented by the Cenomanian, Turonian, Santonian and Maastrichtian, are mainly composed of carbonates with few shale and marl intercalations. This sequence was accumulated under lagoonal to neritic and bathyal environments. The structural interpretations of well logs show that the Cretaceous section attains a wide range of dip magnitudes and dispersed azimuths all over the study area, which is probably attributed to tectonic and sedimentological processes. The inherited structural complexities indicate possible rejuvenations along old fault planes and rotation of the faulted blocks.

Highlights

The purpose of this paper is to evaluate the geological context of the subsurface Cretaceous sequence of North Sinai, as a promising hydrocarbon province, with particular emphasis to the depositional environments, sedimentological and structural characteristics
1) Environmental and Facies Interpretations The natural gamma ray spectrometry (NGS), HDT and the SHDT logs were used for defining the depositional environments and facies characteristics of the subsurface Cretaceous section in the study area
The interpretation of the dipmeter patterns and the NGS logs can be used for defining the depositional environments, while the Th/K logs of the NGS tool are used successfully for identifying the clay and detritus minerals of the studied interval

Summary

Introduction

The geological framework and structural evolution of the North Sinai have been. Five regional unconformities were observed and mapped on seismic sections in the study area. These tectonosequence boundaries reflect major changes in regional tectonic settings [1]. Most of the mapped structures in offshore North Sinai are located within five NE-oriented inverted structures, whereas the intervening areas are undeformed or only slightly deformed. Three phases of structural deformation affected the Mesozoic-Cenozoic succession in offshore North Sinai. Despite a relatively complex history, the Phanerozoic geological framework of Egypt is highly prospective for oil and gas and eight major tectono-stratigraphic events have created multiple reservoir and seal combinations [4]

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