Structural Analyses and Evolution and Its Implication for Petroleum System and Exploration Play Concepts of Offshore North Sumatra Basin

The Offshore North Sumatra Basin is part of the profilic North Sumatra Basin, which has experienced a complex tectonic history since the Eocene, including rifting, wrenching and compression phases. Historical exploration efforts in NSO have focused on the post-rift basin-fill stratigraphy: carbonate build-ups of the Early & Middle Miocene Peutu and Baong Formations and faulted structures with Late Miocene turbidite objectives (Keutapang Formation). The stratigraphy of the Offshore North Sumatra Basin composes a series of Oligo-Miocene up to Pliocene sediments overlaying unconformably the pre-Tertiary basement complex. Structure analyses indicated an N-S and NW-SE trending horsts and grabens developed within the study area. The basinal lows were filled by continental clastics (Parapat Formation?) and deep marine shales and sands (Bampo Formation). Most Exploration wells penetrated the post-rif succession, and one (1) exploration well DYG-1, penetrated the syn-rift succession and has been used to analyze the petroleum system. Another potential is from the Pre-Tertiary Limestone fracture, as indicated by SLM-1 well. Potential hydrocarbon traps consist of fault-bounded two-way and three-way closures. Hydrocarbons are generally from highly profilic terrestrial and marine shales (Bampo and Baong) and charged from deep basinal kitchens adjacent to structural highs. Petroleum will likely have been Type III Middle Baong and Bampo shales. Hydrocarbons are interpreted to have filled structural, stratigraphic or combination traps.