The Lower Miocene Asmari Formation in Lali oil field, 40 kilometers NW of Masjed-e-Soleyman, is a thick sequence of limestone, argillaceous limestone and dolomitic-anhydritic limestones. At the mentioned area, it lacks the Lower Asmari but contains the Kalhur member and basal anhydrite. The study of the Asmari thin sections from available cores and cuttings at wells no. 20 and 22 of Lali oilfield led to the recognition of 10 MICROFACIES, related to six facies zones, including: supratidal, intertidal, shelf lagoon, barrier or shoal, shallow open marine and basin margin. The Asmari Formation represents sedimentation on a homoclinal carbonate ramp. Diagenetic processes in the Asmari Formation are: physical and chemical compaction, cementation, dissolution and production of mainly vuggy and channel porosities, neomorphism, dolomitization, anhydritization, fractures, micritization and biogenic processes. Fractures have had major effect on the quality of the Asmari reservoir, but vuggy and channel porosities, having less development, have played a less important role in reservoir quality. Results from this study have led to the recognition of marine, meteoric and burial diagenetic environments.