Fracture Types Detected in Eastern Mediterranean Reservoirs (Turkey and Egypt)

R. Nurmi, M. Taha

The dominant fracture systems within eastern Mediterranean oil reservoirs are tectonic in origin, ultimately formed as a result of plate movements. The dominant reservoir fractures in southeast Turkey and northeast Syria are directly related to the anticlinal folding along the Bitlis-Zagros margin, while the main reservoir fractures in Egypt are a function of the plate shearing and wrench faulting which dominated that region.

Most of Turkey's reservoirs are in the fractured Cretaceous Mardin Formation; however, new possibilities in fractured Paleozoic sandstones are being sought. The dominant fractures are fold related and are found on the northern flanks of the asymmetrical anticlines. The strike of these fractures is perpendicular to bedding planes and parallel to dip. There are fewer tear-fault-related and crestal-position fractures, but these may have a greater vertical extent.

Fractures are present in all the producing areas of Egypt except the Nile delta. Basement fractures associated with shear zones in the southern Gulf of Suez have become an important exploration target. Fracture orientations are related to the major shear orientations except where later folding and faulting have caused structural rotation. The development of Zeit Bay field has shown that fractured basement rock can constitute a significant reservoir. The fractured reservoirs in northern Sinai and the Western Desert are in Cretaceous and Jurassic limestones and/or dolomitic limestones. The major shear fractures are parallel to the northwest-north-northwest compressive stresses that formed the reservoir structures; however, local fold- and fault-related fractures are also present.

AAPG Search and Discovery Article #91032©1988 Mediterranean Basins Conference and Exhibition, Nice, France, 25-28 September 1988.