THE DEPOSITIONAL SETTINGS AND THE HYDROCARBON POTENTIAL OF THE NEOTETHYS PASSIVE CONTINENTAL MARGIN

Abstract

The study area is associated with the outer passive wing of the foreland trough that was formed due to collisional-orogenic deformations of the Neotethys Arabian Plate. The sedimentological and paleoenvironmental features of the Cenomanian formation indicate that the carbonate sediments were deposited in a homoclinal ramp depositional settings. The depositional area comprises different bathymetric settings from the intertidal littoral and coastal shallow water to the open and relatively deep sublittoral. Microfacies analysis was performed based on the cores and thin sections observations to investigate the sedimentary and diagenesis evolution. Ten microfacies types are identified showing that carbonates deposited in three major sedimentary facies belts: outer ramp, middle ramp and inner ramp. In response to the relative sea level changes during sedimentation the section comprises of several sedimentary sequences. The sequences mainly reflect the prevailing of twocomponent depositional pattern, i.e., middle ramp and outer ramp, which is a result of low fluctuation of the relative sea level. The complete three-component sequences are associated with predominantly shallow areas that favorable for progradation event even under the low fluctuations of the relative sea level.The highest sedimentation rate is confined to the proximal shallow part of the middle ramp and to the distal part of the inner ramp with favorable conditions for the development of benthic organics due to abundant sunlight and nutrition supply. The best reservoir rocks with intergranular voids, composed of algal oolitic and bioclast grainstones of high dynamic shoal zone.This study provides an insight into reservoir quality prediction and prospect area evaluation of the oil bearing formation in the southern part of stable shelf which is controlled by spatial extension of grain supported deposits of inner ramp and transverse faults.