RESERVOIR CHARACTERIZATION LIMESTONE MINAHAKI FORMATION IN PIA FIELD BANGGAI BASIN CENTRAL SULAWESI

• Main Author: Guspudin, Bagus
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/43286
• Institution: Institut Teknologi Bandung

Minahaki Formation has been proven to produce gas and condensate in Pia field Matindok Area. Minahaki Formation has been identified as a Middle-Late Miocene limestone which consist of reef build-up Mantawa Member and carbonate platform part of Minahaki Formation. Carbonate reservoir characterization is generally more complex than clastic reservoir, it happens because heterogeneity of porosity and permeability correlate with facies distribution and complex diagenetic process. The heterogenity makes it difficult to determine the facies distribution, diagenesis, property and depositional environment. Core analysis result from Pia-2 with 14 thin sections was used to determine lithofacies analysis, diagenesis analysis and depositional environment analysis of Minahaki Formation. Furthermore, Petrophysics analysis in Pia-1 and Pia-2 was conducted to calculate property from limestone Minahaki Formation. Seismic facies analysis was used to determine geometry of Minahaki Formation based on seismic character data. Seismic analysis facies from 3D seismic Pia Field shown type of geometry that reflecting build up and platform characteristic. Meanwhile, seismic inversion analysis using log and seismic data was used to determine the distribution of property that could help interpretation of diagenesis contact occurred in limestone Minahaki formation. Minahaki formation consist of several facies such as: coralline rudstone, coralline floatstone, foraminifera bioclastic wackstone, mollusks bioclastic wackstone and algae packstone. Facies association based on facies analysis was platform margin reef. Limestone Minahaki Formation through diagenesis phase such as marine phreatic, mixing zone, freshwater phreatic and burial that also figured in seismic inversion result. These process was indicated by the presence of micritization, cementation, neomorphism, disolution, stylolite and dolomitization. Based on petrophysical analysis, reef interval Minahaki Formation has porosity around 20-21% and permeability around 489-533 mD better than platform interval with value around 16-17% and permeability value around 297-368 mD. Acustic Impedance indicated value of reservoir property, small value acustic impedance indicated good reservoir property. Seismic inversion analysis reflected that Minahaki Formation associated with vadose and fresh water phreatic diagenetic proccess has value acustic impedance around 5.000-7.500 m/s.gr/cc better than Minahaki Formation that associated to platform carbonate mixing zone diagenetic with acustic impedance value around 7.500-10.000 m/s.gr/cc. Seismic facies analysis section in Minahaki Formation indicated that build-up carbonate character has very clear contact with platform carbonate in the lower part of limestone Minahaki Formation.