Carbonate Reservoir…


Deddy Hasanusi, Kwartono, Rachmat Wijaya



The Mantawa and Minahaki carbonate sequence is the main hydrocarbon bearing reservoir of “S” Gas Field, Central Sulawesi. Carbonate reservoir of Mantawa Formation commonly recognized as pinnacle reef build up type which were growth in the structural high areas. On the other hand, Minahaki limestone is platform carbonate type which dominantly characterized by mud supported facies. In such reservoir, heterogeneity and reservoir distribution is the prime challenge in characterizing the reservoir. This paper describes the reservoir characterization study that focuses on rock type classification and its use on reservoir modeling. In preliminary process, conventional core and well-logs were integrated to obtain reliable information of depositional model, lithofacies, diagenetic history and reservoir rock type. Since cored interval is limited, the interpretation at cored interval was subsequently propagated to un-cored wells using electrofacies approach. Multivariate analysis was applied in order to determine the log type that corresponds with certain facies. It is indicated that sonic, neutron, VGR and secondary porosity index has a good relationship with facies description. Applying these approaches, reservoir rock type was identified and yields three rock type classes representing good, medium and poor quality. Rock type identification result was then up-scaled and co-simulated with AI attribute as secondary parameter. The final rock type distribution was utilized to guide porosity and permeability distribution.


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