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The Banggai Basin, located in Central Sulawesi, is a significant hydrocarbon province with substantial potential. The Toili area, part of the Senoro-Toili Block operated by JOB Pertamina-Medco E&P Tomori Sulawesi, includes the Tiaka oil field. This area is extensively covered by 3D seismic data (acquired in 2018) over an area of 110 km², along with vintage 2D seismic lines from 1981 to 1986.

The primary reservoir targets are Lower Miocene carbonates of the Tomori Formation, while the Minahaki Formation serves as a secondary reservoir. Additionally, the Mantawa Member, characterized by carbonate build-ups, is found within a clastic platform limestone, trending NE-SW across the Banggai Basin. Offshore Toili, the Mantawa layers have been drilled by exploration wells such as Grupa-1, which encountered approximately 1,300 feet of continuous oil shows, Boba-1 (1,300 feet, no shows), and Mantawa-1 (1,800 feet).

Seismic data reveals that the Bubara and Gemintang-Jardini structures, extending in a NE-SW direction, are associated with shallow marine inner shelf environments, which facilitated reef growth. The reservoir was formed during the Late Miocene, following the collision of Sulawesi's eastern arm with the Australian microcontinent. This event led to rapid burial and sedimentation, generating hydrocarbons that migrated into the prospects through the Tomori shale, acting as a carrier bed from the Batui Thrust. This has been proven in the Minahaki Formation, where the Tiaka-1 well recovered 14 BOPD of 19° API oil, and the Tiaka-7ST-2A well tested gas at 7.32 MMSCFD. Lithofacies analysis identified packstone-grainstone facies with 20% porosity and 28% water saturation.

Overall, subsurface and regional analyses of the Bubara and Gemintang-Jardini structures provide strong scientific evidence that carbonate reservoirs in the southern Toili area hold significant hydrocarbon potential, both in terms of oil and gas accumulation.