Lithofacies models of cretaceous reservoirs of the Mesopotamian trough: structural features and distribution patterns

Abstract

The article presents the results of complex multi-scale studies of carbonate natural reservoirs of large and supergiant oil and gas fields of the Mesopotamian trough. Various depositional environments have been identified in the Upper Cretaceous sediments of the Mishrif formation. Facies of tidal channels have been identified and substantiated for the first time at one of the deposits. It is shown that high productivity values are associated with their distribution zones. A fundamentally different type of reservoir is noted in the same-age deposits at another deposit. Here, the main productivity is associated with facies of coral-rudist buildups and shoals. As a result of detailed sedimentological studies and reconstruction of paleobiocenoses of reef-building organisms, the main patterns of the reservoir architecture were revealed. In the Lower Cretaceous deposits of the Yamama formation, coral-stromatoporoid-algae facies and peloid-oolitic shoals have been identified and contoured. Their distribution explains the presence of separate isolated deposits, as well as different positions of water-oil contacts.