Syn- and post-depositional influences on reservoir quality of the Aptian Dariyan Formation, eastern Persian Gulf

The Aptian Dariyan (Shuaiba) Formation, a major Cretaceous reservoir in the Middle East, remains poorly understood regarding the influence of depositional facies and diagenetic processes on reservoir quality. This research addresses the gap through an integrated analysis of facies, petrophysics and geochemistry on a continuous, 104.5 m-long core from the Salman oil/gas field in the eastern Persian Gulf. Employing fully automated techniques, we identified hydraulic flow units (HFUs). We classified nine carbonate facies into three distinct facies associations, arranged from shallowest to deepest: inner ramp (lagoon and shoals), shallow open-marine mid-ramp and deep open-marine (outer ramp and intrashelf basin). These facies associations exhibit a stacking pattern delineating five third-order transgressive–regressive sequences. The identified HFUs include the barrier unit (HFU1), the baffle unit (HFU2) and the normal unit (HFU3), assessed based on lithological and petrophysical attributes. The normal unit, characterized by good storage capacity but poor to moderate flow capacity, highlights the complexity of reservoir quality. The Dariyan Formation is predominantly composed of mud-supported textures formed in warm, tropical waters. Additionally, late diagenetic cementation severely obstructed pore spaces, altered primary rock characteristics and reduced effective flow capacity.