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ABSTRACT: Extensional Block-Faulted Structures of Central Iraq and Oil Finding

Yasin Aljawadi

Several prolific block-faulted structures exist in the near platform of central Iraq, which makes up the western tectonic unit of the Mesopotamian foredeep consisting of East Baghdad, Balad, Samarrah, and Tikrit. These structures form gentle monoclines flanking to the northeast and plunging to the southeast. The structures range from 30 to 100 km in length and consist of growth faults, grabens, and horsts dissected by dip-slip and strike-slip sealing faults. The extension phase was probably initiated by the Kamerian Orogeny that opened the neotethys during the Late Triassic and ended at the close of the Cretaceous by the Laramide orogeny. To the south, growth faulting increased the thickness of the Upper Cretaceous Harth formation, by 200 m, but the lower fans and other T rtiary formations were not increased.

The dipmeter analysis for 26 wells in East Baghdad field indicated the main force that acted on the structure was at N30°E and that the second-order shear forces resulting from it were most effective on the N140°E structure faults.

The oil in East Baghdad Field is contained in multi-layered reservoir blocks. The oils has different gravities and different oil-water contacts. The oil reserves exceed 9 billion bbl for the East Baghdad and Balad structures. Hence this encourages exploration of similar structures in the Baghdad and Balad area.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990