Publications

The determination of porosity and permeability relationship is the major challenge in carbonate reservoir characterization. This relationship is commonly derived from routine core plug analysis combined with thin section description and wireline log data. This paper presents the results of petrophysical rock typing in muddy carbonate reservoirs of Baturaja Formation in Sunda Basin. These reservoirs are analogous to the other Indonesian Tertiary carbonate reservoirs which commonly contain lime mud. The goal of this paper is not to develop a new classification scheme, but to draw attention of the importance of rock type identification as the basis to reservoir characterization and building a reservoir model. More than 500 core plugs were used in this study and each of them was measured for its porosity and permeability and sampled for petrographic analysis. The petrophysical rock type (PRT) identification was carried out by classifying the reservoirs based on their predominant pore types and pore sizes and grouping the associated pores into several rock types. This PRT identification was performed in all depositional facies separately to see the role of depositional facies differences to the PRT development. Six PRTs have been identified from this study, PRT 1 - vuggy porosity and moldic macropore association, PRT 2 - mudstone micropore and moldic macropore association, PRT 3 - intergrain meso-macropore association, PRT 4 - mudstone micropore and moldic mesopore association, PRT 5 - mudstone micropore and intergrain micro-mesopore association, and PRT 6 - mudstone micropore.The data show that different PRT will give differentpermeability value given the same porosity cutoff.Capillary pressure profiles for each PRT also showunique profiles for each PRT, thus giving differentwater saturation at a given height above free water level. These will affect the reservoir pore volume, which in turn will determine the volume ofhydrocarbon in the reservoirs.