Structural characteristics and main controlling factors on petroleum accumulation in Zagros Basin, Middle East

摘要

Zagros Basin is one of the essential basins in the Middle East with the giant oil and gas reserves. It is indicated by regional tectonic and sedimentary evolution, basin structural division, petroleum distribution characteristics and main controlling factors of petroleum accumulation. It has experienced four significant phases which are early Paleozoic intra-Cratonic pull apart basin and platform margin basin, late Paleozoic platform margin basin, Mesozoic passive continental margin basin, and Cenozoic foreland basin. The Zagros Mountain Front Fault and High Zagros Fault divided the basin into foredeep zone, simply folded zone, and Zagros thrust fault zone from southwest to northeast. The oil fields are mainly located in the foredeep zone, while the gas fields are mostly in the simply folded zone and few fields are in the Zagros thrust fault zone. The Lower Cretaceous Kazhdumi Formation mudstone is the main source rock for the Mesozoic, and Cenozoic reservoirs and the Silurian Gahkum Formation mudstone is the main source rock for the Paleozoic reservoirs. The Cenozoic carbonate is main reservoir followed by the Cretaceous Sarvak and upper Permian Dalan carbonate. The evaporite and mudstone are the main seal in the foredeep zone, while the mudstone in the simple anticline zone. The anticline structure and the seal type is the main controlling factor for the petroleum accumulation.