Publications

The tectonostratigraphy of the Central Sumatra Basin is notably unique but remains under-documented due to frequent changes in operatorship, a predominant focus on reservoir-scale studies, restricted data access, and limited knowledge sharing. Although regional studies have resumed over the past five years, they have primarily concentrated on the basin's central region, leaving the eastern area—including the Malacca Block—largely underexplored. This study addresses that gap by providing a comprehensive evaluation of the eastern CSB’s stratigraphy, utilizing an extensive dataset comprising 10,400 km of multi-vintage 2D seismic lines, two 3D volumes covering 551.9 km², 77 wells, 750 feet of core and sidewall cores (SWC), and 21 biostratigraphic reports, culminating in the development of six gross depositional environment (GDE) maps. Three key findings are identified from this research. First, during the Late Eocene to Late Oligocene rifting interval, small normal faults created isolated lacustrine depocenters that later expanded due to tectonic uplift and increased subsidence during the Brown Shale deposition, forming larger lacustrine bodies. Coarse-grained sediments accumulated as fault-scarp aprons, while finer-grained dipslope deltas evolved into subaqueous systems, although the northern areas remained dominated by overfilled sediment plains with limited lacustrine development. By the Late Oligocene, sediment influx from both local and Malayan sources introduced a mix of metamorphic and granitic fragments. Second, during the Early Miocene sagging phase, the Menggala Formation's braided rivers formed a confined, southward-flowing system in the western trough, while the eastern region displayed more sinuous rivers transporting coarse sediments interbedded with coal, indicating the presence of organic banks and floodplains shaped by unrestricted river flow. Third, a major transgressive shift occurred with the deposition of the Sihapas Group and Telisa Formation. Between 22 and 20.5 Ma (Early Miocene), estuarine depositional environments developed, followed by rising sea levels from 20.5 to 16.5 Ma that led to the formation of shallow marine clastic deposits. During this time, the calmer southeastern region supported both coal and carbonate development.