STRUCTURAL MODELS OF TARAKAN, BERAU, AND MUARA SUB-BASIN, NORTHEAST BORNEO

• Main Author: Krisnabudhi, Alfathony
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/55874
• Institution: Institut Teknologi Bandung

The Tarakan Basin is one of the basins with a very high hydrocarbons potential. This basin is divided into 5 sub-basins, namely Berau, Muara, north and south Tarakan, Malinau, and Tidung. The northern Tarakan and Tidung Sub-basins belong to a group of basins that produce hydrocarbons, whereas the Berau, Muara, and southern Tarakan Sub-basins do not have producing wells. That differences are interesting because many hydrocarbon seepages are found in the three sub-basins. Tectonically, the three sub-basins, which are the area of this study, are also bounded by the active structure of Palukoro in the eastern part of the Muara and Tarakan Subbasins. Thus, the study to re-assess geological structures using seismic interpretation and palinspastic reconstruction method can reveal the evolution and structural models in the study area. This research was conducted based on field and subsurface data from 296 2D seismic lines, and 8 exploration wells. The results show 9 sediment sequences from Mesozoic basement to Pleistocene and 6 structural geological models. The Muara Sub-Basin is dominated by planar normal fault with N-S and NW-SE patterns. The southern part of the Tarakan Sub-basin has two structural models, the onshore part is dominated by planar normal fault with N-S direction, while Tarakan deep zone is dominated by thin-skinned structures from listric and toe-thrust system. The Berau Sub-basin has a fairly complex structure, the western part is controlled by a contractional horsetail structure caused by the movement of Benggara Fault Zone (BFZ), the eastern and northern parts are dominated by the en-echelon structure caused by the movement of Latih Fault Zone (LFZ), while the central part is controlled by a restraining overstep structure between two sinistral strike slip fault of Latih Fault Zone (LFZ) and North Mangkalihat Fault Zone (NMFZ). The total contractional strain obtained from palinspastic reconstruction is -7.57% while the extensional is 11.80%. This reconstruction also shows that there is a structural inversion in the western zone of the Berau Sub-basin. The existence of the BFZ fault with NW-SE direction form series of thrust fault system with NE-SW direction. The existence of this thrust fault system causes the pre-exiting Paleogene structure to experience an inversion in the late Neogene-Plistocene period. The existence of the sinistral strike slip system with a NW-SE direction correlates with the presence of a collision process in northwest Kalimantan and a counterclockwise rotation from the island of Borneo in the Neogene period so that the structural model in the Berau Sub-Basin is controlled by sinistral strike slip fault system. The collision process also affects the structural model in the Tarakan deep zone, the regression phase in that period causes very rapid sedimentation so that this zone is dominated by thin-skinned structure types with detachment at the SB-5 level. The existence of the sinistral strike slip system is the main controlling factor for the division of the basin boundaries and the presence of hydrocarbons in the study area.