Depositional Nature of the Triassic Jilh Lower Carbonates: A Proven Hydrocarbon Play in West Kuwait Area

Jilh carbonate succession represents Middle to Late Triassic stratigraphy in Kuwait. It is deposited in shallow marine inner ramp and restricted settings. Three major lithofacies units are recognized based on well data: Jilh Lower Carbonates which is overlying the Early Triassic Sudair Formation, Jilh Dolomite in the middle and Jilh Upper Carbonates. A thin salt layer, near absent at places, separates the bottom unit from the upper ones. The entire sequence from top to bottom is characterized by numerous thin anhydrite layers, exhibiting prevalence of arid climate. Whereas Jilh Dolomite and Upper Carbonate sequences are regionally consistent with near uniform thickness, the bottom unit occurs with highly varying thickness ranging from 300’ to 800’. Increase in thickness is seen mainly in the western parts of Kuwait where it is also referred to as ‘Kra AlMaru’ Unit. It comprises mainly dolowackestone and dolomudstones. Good amount oil and gas flowed from these reservoirs during initial testing in a couple of wells. Therefore, the depositional pattern may be interesting from the oil exploration point of view.