ABSTRACT

The present-day Gulf of Suez Basin was initiated during the Oligocene as a result of relative motion between the Arabian, Nubian, and Sinai plates. At that time, pre-Miocene sediments were broken into fault blocks that were rotated and then inundated by the organically rich "globigerina" marls and shales of the Lower Miocene. These Lower Miocene sediments served as the primary source of the oil and gas found in the Gulf of Suez Basin, while the rotated pre-Miocene blocks formed structural focal points for the accumulation of the hydrocarbons generated. Subsequent deposition of-the thick and widespread Middle Miocene evaporites ensured that all the generated hydrocarbons were sealed in the basin in reservoirs ranging in age from Miocene to Devonian.

INTRODUCTION

The most prolific and prospective oil province in Egypt is the Gulf of Suez Basin. Its productive history can be traced back to ancient times with oil being recovered from seepages at Gebel el Zeit and Gemsa by the Pharaohs. To date, 3.5 to 4.0 billion bbl of recoverable oil have been discovered in 24 oil fields within the basin. In spite of its long history of production and exploration, it is only in recent years with improved seismic and renewed exploratory drilling that the petroleum geology of: the basin has been fully understood.

The Gulf of Suez Basin encompasses and, in General, parallels the coastline of the Gulf of Suez (Fig. 1). The basin extends, in an east-west direction, from the Sinai Shield on the east to the Esh EI Mellaha Shield, in the Eastern Desert on the west. The average distance between these shield masses is 54 miles. In a north-south direction, the basin's northern limit lies just north of Suez City and extends to the south to Hurghada, a distance-of approximately 210 miles.

EVOLUTION OF THE GULF OF SUEZ BASIN

The Gulf of Suez has formed primarily as a result of tensional movements, and ensuing subsidence, which to a minor degree occurred as early as Paleozoic times. Since these times, the formation of the Gulf of Suez has taken place in a number of distinct evolutionary stages (Fig. 2). The presence of Devonian or older sandstones and Carboniferous black shales in numerous wells is evidence that a depression approximately coinciding with the Gulf of Suez existed at least as early as Carboniferous times. However, the thicknesses of these Paleozoic rocks are relatively minor compared with those of the main Paleozoic basin in the western and southwestern regions of Egypt. This comparison leads to the hypothesis that the Paleozoic rocks in the Gulf of Suez region were formed in an embayment that extended from the Mediterranean area southward to Hurghada at the mouth of the Red Sea.8,12,16

A hiatus caused by the Hercynian epeirogeny precluded sedimentation in the Gulf for a considerable time following the Paleozoic deposition. This is noticeable particularly further south, where commonly Upper Cretaceous deposits (Cenomanian) rest uncomfortably upon Lower Carboniferous black shales.

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