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Sibolga Basin is a fore-arc basin, located in northwest of North-Sumatera Province. The borders of Sibolga Basin are Andaman Sea at north, Nias Island at south, Sumatera Island at east, and Hindia Ocean at west.Directly, structural pattern that was developed in Sibolga Basin is related to Semangko Fault and Mentawai Fault. This fault developed since Mesozoikum and continued to tertiary, then reactivated in Pliocene. The stratigraphy succesion at Sibolga Basin can be divided into five lithology units, i.e. Basal Unit, Clastic Miocene Unit, Carbonate Middle-Miocene Unit, Carbonate Late- Miocene Unit, and Pliocene-Plistocene Unit.Based on seismic and well log data: Source rocks of Sibolga Basin are Basal Miocene Clastic unit, Carbonate Middle Miocene, and pre-Neogene sedimentary rocks. Reservoirs of Sibolga Basin are Carbonate Middle Miocene, transgressive unit I, Carbonate Unit II, and transgrassive unit II. Stratigraphic and structural traps are seen in seismic and well log data. Reef carbonate in Carbonate Unit II, Middle Miocene to Pliocene, is a stratigraphic and structural traps shown by anticline shape which is formed in Pliocene. The result from well log and seismic data shows that location of seal rock in clastic unit upward is pro-delta to inner neritic facieses. Migration at Sibolga Basin occurred in Pliocene to Plistocene period.