Shipwreck of MV Boelongan Nederland situated in offshore of Mandeh Bay of West Sumatera is announced as potential area for tourism destination. Many studies were produced in term of its archeological and historical side but there is no significant work in sedimentological aspect. It is critical to understand depositional process of study area regarding the design of construction to minimize the impact of dynamic activity of waves within the area. Moreover, some areas along Mandeh Bay are covered by Cubadak Island as a protection for wave action derived from Indian Ocean that can produce more complexity in depositional process and will reflect to its characteristic of grain-size profiles. Utilizing thirteen sediment samples in two areas that correspond to inside (Mandeh Bar) and outside (Nyalo Bar) coverage of Cubadak Island, this study attempted to compare and contrast both grain-size profiles as well as interpretation of depositional process based on well-known analysis such as bivariate scatter plots, Linear Discriminant Function plot (LDF), Log probability curves and C-M diagram. Result of this study can be integrated by other researches to gain better policy in maintaining the shipwreck conservation. High energy of Indian Ocean wave supported by strong current clearly dominated depositional process in Nyalo Bar with coarser grain-size; good sortation, lower Y2 of LDF plot; extremely high population of traction materials and lower range of C-M. By contrast, presence of Cubadak Island disrupted the wave effectively and created lower and fluctuated energy in Mandeh Bar. This phenomenon was clearly depicted in its characteristic of finer grain-size with higher Y2 value; high abundance of saltation materials and greater ratio of C-M value.

Located in the north-western part of Bonaparte Basin, offshore western Timor presents the opportunity for a distinct exploration concept due to the discovery of the Abadi gas field. A classic Jurassic petroleum play did not develop as a proven reservoir and source rock in the study area due to severe erosion during the Valanginian event. Therefore, the Triassic interval requires assessment to reveal an alternative petroleum system in the study area. A petroleum system analysis utilising 2D seismic lines and three exploration wells was performed to construct a new exploration concept. The study showed that the Scythian Mount Goodwin interval could be considered a primary gas-prone source rock, with type II/III kerogen, a total organic content up to 2.09% and a hydrogen index that could reach 569 mg/g. Based on a study of a pseudo-well conducted here, the Mount Goodwin interval is found to have reached gas generation in the Early Cretaceous and expulsion in the Early Eocene. The potential reservoir rocks are the Carnian-Ladinian Challis and Anisian Pollard intervals. The Challis interval, the primary reservoir, has typical shoreline sandstones and is interbedded with claystones and limestone intercalations. Petrophysical and petrographic studies in this interval indicate good reservoir properties. However, the Pollard interval mainly consists of carbonates with minor claystones and has a low quality of reservoir properties. The intraformational shale of the Challis is considered as the potential regional seal, especially within areas that are not truncated by the Valanginian event. From the perspective of exploration, the Jurassic north-east-south-west-tilted fault blocks are still favourable for new discoveries in the offshore western Timor area.

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South Makassar Basin Depocenter (SMBD) is located in Southern Makassar Strait which has petroleum potential by the presence of oil and gas indications within the area based on Airborne Laser Fluorescence survey. However, detail studies within this area are not developed well. One of the studies which can be utilized for further discoveries of oil and gas field in SMBD is a study of depositional model using seismic facies method to maximize limited seismic and well data. Interpretation of depositional model in Eocene (syn-rift phase) was varied from alluvial plain and alluvial fan complex, continued gradually to platform. In Oligocene time (post-rift phase), massive transgression caused a major deepening in entire SMBD where the depositional environment changed to basinal plain. In early Miocene – recent interval (syn-orogenic phase), SMBD was relatively in stable condition at basinal plain environment. Lower Tanjung Sequence will be the most prolific petroleum play in SMBD due to its adequate source rock, reservoir rock and seal rock as well. Keywords: South Makassar basin, depositional model, seismic facies