RESERVOIR CHARACTERIZATION FOR THIN LAYERS USING STOCHASTIC INVERSION AND SEISMIC ATTRIBUTES, STUDY CASE: LOWER TERUMBU FORMATION, EAST NATUNA BASIN

• Main Author: Wahyuzi, A.Meickloni
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/83098
• Institution: Institut Teknologi Bandung

Oil and natural gas production in Indonesia is decreasing (BPS, 2023), meanwhile according to data on projected energy needs in Indonesia released by BPS, it shows an increasing graph until 2050 reaching 2.91 barrels of oil equivalent, to meet these needs the volume of Indonesia's oil imports is increasing. Therefore, exploration activities to obtain new reserves continue to be carried out. The East Natuna Basin is one of the hydrocarbon-producing basins, especially gas, in Indonesia. This study focuses on the Lower Terumbu Formation located in the East Natuna Basin. The lithology of this formation is a mixture of shale rock and thin sandstone, so a method that can separate the two lithologies well is needed. Analysis of well log data shows that AI and VpVs Ratio are sensitive elastic parameters. Stochastic inversion seismic method was used to model the thin reservoir with thickness below the tunning thickness. The method was approached through the AVO Two Term and Extended Elastic Impedance (EEI) equations. The results of the inversion data of elastic parameters AI-VpVs Ratio value show a linear data relationship obtained from regression, while the petrophysical parameters have a nonlinear trend. From these problems, reservoir characterization is carried out using CPEI and PEIL attributes. The reservoir characterization approach is carried out on the petrophysical parameters to be analyzed, namely porosity through PEIL Attributes to see the compaction trend as well as Pseudo-Porosity and Pseudo-water saturation through CPEI Attributes to see the fluid trend. The 25 realizations formed are equiprobable, therefore an uncertainty analysis approach was taken to determine P10, P50, and P90 through Hydrocarbon Pore Volume (HCPV). It was found that the 18th realization represents P50 as the volume to be used for horizontal interpretation. The study showed low values of AI, VpVs Ratio, CPEI, PEIL, and water saturation, and high porosity indicating that the Lower Reef Formation is a porous shally sandstone and indicated to contain hydrocarbon fluids.