GEOMETRY EVALUATION AND FAULT SYSTEM OF TARAKAN SUBBASIN USING GRAVITY DATA

• Main Author: Eko Kurniawan, Arieffian
• Format: Theses
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/79364
• Institution: Institut Teknologi Bandung

The latest survey of gravity data using aircraft covering the Tarakan Subbasin area is a significant additional data because there is no direct measured gravity data offshore of North Kalimantan. Evaluation using gravity data, combine with existing seismic and wells data will complement the subsurface evaluation of the Tarakan Sub-basin area to be more certain. The gravity data that has been processed to obtain Bouguer corrected gravity data is analysed to obtain geometry and trends of the geological structures in the Tarakan Subbasin. Gravity data analysis was also carried out to obtain differences in the separation of fault systems in the Tarakan Sub-basin based on the lineament trends of the gravity data. The stages in the research are using gravity data, 2D seismic and rock density data from wells which are used as a reference for rock density values. Separation of deep and shallow source gravity anomalies is carried out using frequency spectrum analysis obtained for the estimated depth of 12km for deep while for shallow sources 5km, attributes of First Vertical Derivative (FVD) and Total Horizontal Gradient (THG) gravity data. The seismic data of the study area which has been calibrated with the well data is interpreted to obtain a depth structure map for each geological stage. The source gravity anomaly map in providing an irregular shape geometry of the Tarakan Subbasin is irregular ellips with the south-eastern boundaries cannot be identified because its has connected with Sulawesi Sea.The THG attribute gravity anomaly data can be used to interpret the direction of continuity of geological structures with boundaries and differences in fault systems that can be better separated. The direction of continuity of the structure trending Northwest - Southeast is correlated with strike- slip faults while the direction of continuity of the structure trending Northeast - Southwest is correlated with normal faults and growth faults. The results of rock density modeling using gravity data can be used to estimate the depth of basement with an estimated depth of basement ranging up to 9km with basement is modelled as a transitional of continental crust and oceanic crust