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The basement igneous intrusive rock lithology in the South Sumatra Basin was previously suggested to be a solely granitic rock. It is also a common knowledge that the Miocene Baturaja Formation carbonates are one of the prolific reservoirs. However, after a comprehensive reservoir recharacterization had been conducted in the Suban Field, new insights regarding these two rock types were revealed. The basement lithology consists of a more complex metasediment containing Andesite, Granodiorite, and Gabbro and an Oligocene-age carbonate reservoir was also identified. The reservoir recharacterization was carried out by conducting an integrated analysis to reconstruct the complex reservoir configuration utilizing seismic data, core, cuttings, absolute age dating, and biostratigraphy. Seismic data was utilized as a general framework for reservoir architecture due to the resolution that allowed to describe the reservoir configuration in detail. Core and cuttings were used to identify the reservoir facies, and absolute age dating along with biostratigraphy were used to construct geochronology for each reservoir facies. Finally, well to well correlation was performed to reconstruct complex reservoir configurations. The result of the study indicated that the reservoir age in the field can be divided into two parts, pre-Tertiary (PRT) basement and Tertiary sediments. The PRT of Suban Field comprises several types of crystalline rock that will have different respond to the stresses and the Tertiary section that consists of clastic and several carbonate facies of different ages that vary across the study area. This study offers new insights regarding the basement configuration and the emerging carbonate play. Different igneous rock compositions reflect a complex magmatism process in South Sumatra. Oligocene carbonates that were identified in Suban could open the opportunity to discover a hydrocarbon-bearing Oligocene carbonate play in the South Sumatra Basin. |
