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|a Zaman Field is located approximately 150 km from Palembang City, in the South Sumatera Basin. The gas field comprises a carbonate reservoir that managed by the Pertamina EP located in Baturaja Formation. Baturaja Formation has a problem with heterogeneity and became necessary to perform the task of reservoir characterization in order to solve this problem. Thus, the objective of this study was to characterize the carbonate reservoir of Baturaja Formation by distributing petrophysical rock types, porosity, and permeability. Petrophysical rock type is one of the considered methods to understand reservoir heterogeneity. Winland R35 and flow zone indicator were performed to determine which method was more reliable for Zaman Field. Transform permeability was applied as a validation control in petrophysical rock type classification and Winland R35 method showed a better result than flow zone indicator method thus Winland R35 was utilised as an indicator of reservoir heterogeneity which divided the petrophysical rock type based on its pore throat size. This has produced four petrophysical rock types, which depend on specific porosity and permeability trends. Petrophysical rock type 1 was identified as having the biggest pore throat size, with petrophysical rock type has 4 the smallest pore throat size. Using a geostatic model it was possible to perform the distribution of petrophysical rock type, porosity, and permeability in the form of 3D model. As a result, it showed that petrophysical rock type 1 and 2 were well developed in the Upper Baturaja with estimated porosity values from 6.1 to 20% while permeability values from 2.2 to 13 md. Lower Baturaja was dominated by petrophysical rock type 3 and 4 with porosity values from 3.2 to 10.9% while permeability values from 0.1 to 0.2 md. The results of this study can be used as an additional data to improve reservoir description and the main input for a dynamic simulation and further development planning in Zaman Field.
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