Middle East Cretaceous Structure and Isopachs

CHRISTIAN, LOUIS

The world's second largest oil field-Burgan-Kuwait and the world's largest offshore oil field-Safaniya-Saudi Arabia produce from Cretaceous deltaic sandstones. These reservoirs are thickest in the western shelf, inter-fingering eastward with basinward shales and carbonates.

At Top Cretaceous 2,000 ft. contours show giant oil field structures on the Saudi side of the Gulf, such as the Ghawar and Qatar Anticlines, and major fault trends extending northward into Iraq, Jordan and Syria.

Stratigraphic mapping reveals several significant trends: 1. Lower Cretaceous carbonate-shale-evaporite facies in the offshore Gulf-Emirates include Thamama Formation carbonate pays, sealed by interbedded anhydrites. Equivalent Zubair Formation deltaic sandstones in the western Saudi-Iraq shelf contain thick, permeable oil producing reservoirs. 2. Following Middle Cretaceous sealevel regression, deltaic sandstones were deposited eastward into the basin at least as far as Qatar, Kuwait, coastal Iran, and Central Iraq. Giant producing reservoirs include Nahr-Umr, Safaniya, Khafji, and Burgan. Between East Baghdad and Zubair (near the Kuwait border) this deltaic shelf edge remains insufficiently explored for a distance of 400 kilometers. 3. Deep turbidites and olistostromes along the Oman Mtn. and Zagros Fault basin margins resulted from Coniacian and younger subduction beneath Iran, and marine trangression extended west across the Arabian Shelf. 

AAPG Search and Discovery Article #91021©1997 AAPG Annual Convention, Dallas, Texas.