Investigating the role of basement structures in controlling facies characteristics, depositional models, and diagenetic alterations of the Sarvak Formation in the eastern and western regions of the Persian Gulf

The Sarvak Formation, as one of Iran's most important hydrocarbon reservoirs, has been deposited and evolved under active tectonic conditions in various regions of the Zagros, including the Persian Gulf. The present study aims to investigate the effects of tectonic activities on the facies characteristics and diagenetic history of the Sarvak Formation in the eastern and western regions of the Persian Gulf. Facies analysis results indicate the deposition of the Sarvak Formation on a carbonate platform of ramp type. In the eastern part of the Persian Gulf, sedimentary facies of the Mishrif Member (Upper Sarvak) are predominantly deposited in inner platform areas (lagoon, shoal, reef deposits), while facies of the Khatiyah Member (Lower Sarvak) are mainly found in deep and outer platform areas (outer ramp). In the western part of the Persian Gulf, the Sarvak Formation encompasses a spectrum of shallow to deep-water facies, with open marine facies (middle and outer ramp) being notably more abundant. Two lower-order sequences (fourth-order) and one higher-order sequence (third-order) have been identified in this formation, indicating a high correlation with other areas of the Zagros and the Arabian Plate. Diagenetic effects related to a palaeoexposure surface have been observed in the uppermost part of the Sarvak Formation in both the eastern and western regions of the Persian Gulf. Dissolution porosity, brecciation, and iron oxide staining are among the most important diagenetic processes associated with these exposure surfaces. The thickness of the Sarvak Formation shows considerable variations in different parts of the Persian Gulf. Additionally, sedimentary facies of this formation exhibit significant lateral variations. The changes in thickness and facies variability of the Sarvak Formation were directly related to basement structures, indicating their activity during the deposition of this formation in the Persian Gulf. These tectonic events have had a significant impact on the burial history of the Sarvak Formation. Ultimately, the culmination of these facies and diagenetic characteristics has influenced the reservoir quality of the Sarvak Formation in the study areas.