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The Mesozoic Source Rock Identification in Tomori Basin, East Arm of Sulawesi its Implication for Petroleum Play

Proceedings Title : Proc. Indon. Petrol. Assoc., Technical Symposium, Indonesia Exploration: Where From - Where To, 2016

Tomori Basin occupies the area of Morowali, North Morowali, and the offshore of Tolo Bay, East Arm of Sulawesi. This basin is unique as it becomes the location of collision between Sundaland, Banggai-Sula microcontinent, and East Sulawesi Ophiolite. The stratigraphy of Tomori Basin reflected the poly tectonic of this basin. The Mesozoic sediments originated from microcontinent, consist of Triassic to Jurassic of Tokala Formation, Upper Jurassic of Nanaka and syn-drifting carbonate sediment of Tetambahu Formation. Those Formations are coeval to Bobong and Buya Formations in Banggai Basin. Above the Paleocene hiatus deposited the Eocene-Oligocene Salodik limestone, covered by post collision sediments of Pliocene to Pleistocene Tomata and Larona Formations. Source rock potential analysis had been done for Mesozoic Tokala, Nanaka and Tetambahu shale and organic claystone. Total organic content from those sediments ranges from 0.32% to 3.46%. Hydrogen Index value shows the domination of type III kerogen (gas and oil prone) with slightly mixture of type IV kerogen. Tmax measurement shows immature to marginally mature hydrocarbon (428oC to 432oC), but this result are not fully agree with the result from vitrinite reflectance and TAI data. Mean vitrinite reflectance values range from 0.56% Ro to 0.76 Ro, suggest the sediments are marginally mature to peak mature, which is in a good agreement with TAI data (2 to 2.5, early mature). The result from source rock analysis suggests that reservoir charging in Tomori Basin is not only from the proven Cenozoic sediment but possibly from the Mesozoic sediments as the implication of its polytectonic history.

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