--> Sequence Stratigraphy And Hydrocarbon Prospectivity Of The Frontier Neogene Basins In Se Sulawesi, Indonesia

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Sequence Stratigraphy And Hydrocarbon Prospectivity Of The Frontier Neogene Basins In Se Sulawesi, Indonesia


The Neogene basins in SE Sulawesi preserve thick sedimentary deposits and are potential hydrocarbon-bearing basins. SE Sulawesi has been explored since the 19th Century because of its significant asphalt deposits in Buton Island. However, due to its complex structure and lack of well-constrained data concerning age, most of the formations have been assigned to the Celebes Molasse. New data from this study based on mineralogical, palaeontological, zircon geochronological analyses and seismic interpretation have shown that Celebes Molasse sediments have significant variations in timing of deposition and composition. The Neogene basins of SE Sulawesi, including the Bone and Buton basins can be broadly correlated based on similarities in age, sedimentary provenance and sequence stratigraphy. Several geological events including major depositional changes, unconformities and correlative conformity surfaces are identified in the SE Arm, Bone Bay and Buton Island and can be used to address the problem of structural and stratigraphic evolution. The Neogene stratigraphy of SE Sulawesi can be divided into Lower Miocene, Middle to Upper Miocene, Pliocene, and Pleistocene mega-sequences that are separated by five regional unconformities with ages of (1) Early Miocene (c. 23 Ma), (2) Middle Miocene (c. 15 Ma), (3) Latest Miocene-Earliest Pliocene (c. 6-5.3 Ma), (4) Early Pleistocene (c. 1.8 Ma) and (5) Middle Pleistocene (c. 1 Ma). Sequence stratigraphic interpretation reveals that the Middle to Upper Miocene sediments in Bone and Buton Basins represent the deeper-water distal equivalent of the SE Arm’s basin margin. Better understanding of the Neogene stratigraphy and source to sink history in SE Sulawesi can be used to reconsider the Neogene hydrocarbon prospectivity of Buton and Bone Basins. A proven Neogene source rock is indicated by the oil seeps and shows from wells in the Buton Basin. The neighboring Bone Basin potentially has a comparable mature source rock. The potential reservoirs are Upper Miocene highstand-delta, forced regressive-uppermost Miocene downlapping delta and deep-water submarine fans, Lower Pliocene shelf edge deltas and submarine fans, and Pliocene transgressive backstepping and pinnacle carbonates. The best seal is Plio-Pleistocene transgressive shales. Recognition of stratigraphic sequences helps in better understanding of the basin history and in building the geological models that underpin play assessment.