Delineating subbasins of sedimentary rock structure beneath eastern Central Sumatra Basin based on gravity model, seismic profiles, and well-log data: A case study

The Central Sumatra Basin is a vast sedimentary basin that has been proven to produce hydrocarbon. The basin comprises several subbasins that are not sufficiently imaged by conventional seismic reflection profiles and limited well-log data, particularly in the nearshore area to the east. This research aims to delineate sedimentary subbasins, interpret the subsurface geologic model, and identify geologic structures beneath the eastern part of the Central Sumatra Basin using integrated geophysical gravity, seismic profiles, and well-log data. Three-dimensional gravity inversion modeling results indicate that the pre-Tertiary granitic basement is a continental crust with a mass density value of 2.67 gr/cc. The modeling results indicate that the sedimentary rock is composed of Early Oligocene–Middle Miocene sedimentary rock, with a mass density of 2.35 gr/cc, arranged from bottom to top. The residual gravity anomaly model identifies 13 sedimentary subbasins with structural features such as basement height, graben, and fault mapped in a relatively northwest–southeast direction. Moreover, based on the graben pattern and the basement high beneath the eastern Central Sumatra Basin, many structural patterns support the development of petroleum systems similar to that of the western part of the basin, which has already produced hydrocarbon. Our research also revealed the thickness of the Sihapas Formation in the eastern part of the basin, which shows great potential as a hydrocarbon reservoir. The results show that integrated analysis of many geophysical data sets can substantially decrease the uncertainty associated with individual data sets and produce more reliable imaging of subsurface geology.