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The Sangatta area is located on the north of the Mahakam Delta in East Kalimantan, and belongs to the Kutei Basin. Sediments of Lower Miocene to Pliocene in the Sangatta area comprise the Pamaluan Formation, Pulubalang Formation, Balikpapan Formation and Kampungbaru Formation.Geochemical study of these sediments shows that shales of the Balikpapan Formation have a high content of organic carbon, and the kerogens are classified as Type I1 or I11 by pyrolysis (Rock Eva1 analysis), and herbaceous or coalyl woody type by visual kerogen analysis. In the Sangatta field, the maturity level of source rocks reaches the oil generation zone (Vitrinite Reflectance: Ro >0.5) at a depth of 800 meters. Biomarker analysis indicates that the crude oils produced from the reservoir are correlated to the source rocks approximately 500 meters deeper than the reservoir.Based on the well data and geochemical data, the MINI BSS, a computerized simulation model, was applied to evaluate hydrocarbon generation and migration during the basin development. The simulation shows that the oils produced from the Sangatta field migrated to the trap from the source rocks of the middle-upper Middle Miocene (Mid. Mio I1 & I11 in Fig. 2) on the flank of the Sangatta anticline through interbedded carrier rocks during Late Miocene to Pliocene.