Petroleum System and Hydrocarbon Prospectivity of the Simenggaris Block and Its Surrounding Areas, Tarakan Basin, East Kalimantan, Indonesia: A New Approach Using Sequence Stratigraphy

Noeradi, Dardji¹, Bambang P. Muritno², . Sukowitono², Eddy A. Subroto¹,. Djuhaeni¹ (1) Institute of Technology, Bandung (ITB), Bandung, Indonesia (2) Joint Operation Body (JOB) Pertamina-Medco Simenggaris Pty. Ltd, Bandung, Indonesia

Hydrocarbon exploration in the Tarakan Basin has been started since more than fifty years ago. The discovery of Bunyu and Tarakan fields proves that the petroleum system is working in this basin, especially in the eastern part. Tectonically, Tarakan Basin is a complex multi-stories basin, starting from rifting in the early Tertiary time, followed by passive mar­gin and foreland basin development toward the end of Tertiary. The complexity of the basin is more pronounce due to deltaic tectonism especially in the eastern part of the basin. Closures of inversion thrust faults of Plio-Pleistocene tectonic compression products have been developed in the several parts and acted as one of the proven hydrocarbon bearing traps in this basin.

However, hydrocarbon exploration in the western part of the basin only encountered marginal accumulation of oil and gas. To obtain new hydrocarbon potential area(s), a new different approach based on an integration study between stratigraphic framework and geo­chemistry has been conducted to analyze the petroleum system of the basin. Sequence stratigraphic framework has been established in the Simenggaris block using biostratigra­phy, well log, as well as 2D & 3D seismic data. Eight sequences of Oligocene to Pliocene age have been identified and they are bounded respectively from older (SB1) to younger (SB8). Geochemically, source rock analyses comprising richness assessment, kerogen types, and maturity have been conducted for each sequence to model the kitchen and hydrocarbon migration pathways. Furthermore, burial history based on eleven wells, has been used to analyze maturity, tectonic subsidence, and structural trap formation. By understanding the

petroleum system of the area using the new approach, it is hoped that it will be able to be used as a guidance to plan the prospect rank more accurately and, broader, the exploration development strategic plan within the area.