A thorough qualitative and quantitative interpretation has been made on carbonate sediments from Central Luconia, using microfacies study paired with published geological reports. In this study, the relationship between depositional environments and diagenetic alteration of EX Field, located in the southwest of Central Luconia Province, offshore Sarawak were investigated using core description and microfacies study. Seven facies (F1-F7) were identified from EX-2 and EX-3 wells based on the lithology, texture, fossil assemblages and depositional environment. Each of the facies has been diagenetically altered extensively by micritization, cementation, neomorphism, dolomitization, compaction, and fracturing. Carbonate typically has calcite, dolomite and occasionally other mineral such as pyrite and clay especially those that formed in high sea level/ transgressive unit. The presence of clay mineral during deposition has influenced the diagenetic alteration of the EX Field. A geochemical and stable isotope analysis would provide more information on the pore fluid. © 2020. All Rights Reserved.