Carbonate reservoirs demand special attention due to their substantial contribution to global oil and gas reserves. In fact, these reservoirs account for approximately 60% of the world's remaining oil and gas reserves. Moreover, they naturally exhibit numerous favorable attributes for carbon dioxide (CO2) storage. As such, the continued exploration and development of these reservoirs are not just essential for meeting future global energy demands, but they also play a crucial role in achieving net-zero carbon emissions by utilizing depleted reservoirs as sinks for CO2 sequestration. The quality of these reservoirs, particularly their porosity and permeability, is significantly influenced by a variety of factors including their depositional environment and diagenetic evolution. Thus, conducting research in these areas offers a unique opportunity to predict reservoir properties and gain an understanding of their distribution and evolution. The Lower Aptian Carbonates, namely the Lower Shu’aiba and its equivalent, the Upper Qishn, are widely recognized in the Arabian Peninsula for their substantial hydrocarbon reserves presenting an excellent opportunity for studying and evaluating the depositional environment and the impact of diagenetic modifications, which can further the understanding of reservoir quality. Approximately 59 m of the outcropped Lower Shu’aiba in Wadi Bani Kharus and 22 m of the outcropped Upper Qishn in Wadi Baw were studied for facies analysis, diagenesis, and reservoir quality. A total of 26 selected samples were collected from both outcrops, all of which were used to prepare thin sections. These were then studied under a microscope and subjected to point counting (300 points). Of these samples, 12 were further analyzed using Scanning Electron Microscopy (SEM) and geochemical analyses, including X-ray Fluorescence (XRF), X-ray Diffraction (XRD), and Energy-Dispersive X-ray Spectroscopy (EDS). Additionally, 16 samples underwent coring and porosity and permeability measurements. In the investigated sites of Wadi Baw in East Central Oman and Wadi Bani Kharus in North Oman, 17 different microfacies have been identified deposited in a diverse array of depositional environments namely, lagoon, reef, open marine-algal platform, and open marine-slope, underscoring a clear gradational transition from proximal to distal settings. The deeper, distal part of the basin is represented by Wadi Bani Kharus with its distinctive slope microfacies, while Wadi Baw, with its coarser-grained lithofacies, is indicative of the proximal, high-energy environment. Regional variations in diagenetic alterations have been noted, influencing the reservoir quality of the Lower Aptian Carbonates. Specifically, these variations are evident when comparing the Lower Shu’aiba of Northern Oman to the Upper Qishn in Central Oman. The northern region is marked by pronounced fracturing and subsequent calcite cementation that fills these fractures, while Central Oman shows a strong presence of dolomitization and dissolution. Notably, the Upper Qishn in Wadi Baw is home to unique dolomite microfacies. These microfacies present a classification challenge due to their non-mimetic nature and suggest the presence of dolomitization mechanisms in Central Oman that aren't found in the north. Such diagenetic changes play a crucial role in determining the reservoir quality in both areas. The microfacies, which are indicative of the depositional environment, play a role in determining reservoir quality. In particular, the presence of interparticle microporosity and intrafossil porosity, especially within microfacies containing foraminifera, significantly boosts the overall reservoir quality. While the Lower Aptian Carbonates display high porosity, their permeability remains low due to limited pore interconnectivity. In Wadi Baw, these carbonates have higher porosity and permeability values than in Wadi Bani Kharus, where the porosity is poor, and permeability is nil. This disparity can be attributed to the different burial depths experienced by these regions; Wadi Baw underwent shallow burial, whereas Wadi Bani Kharus was subjected to deep burial during the ophiolite obduction. The Upper Qishn emerged from preliminary assessments as a promising site for Carbon dioxide (CO2) storage. Despite slightly below-threshold permeability, the formation's favorable average porosity, thickness, and depth indicated potential for efficient supercritical CO2 storage. Geochemical analyses further revealed the formation's mineralogical suitability for stable, long-term CO2 storage via mineralization.