Integrated analysis of inversion acoustic impedance method and spectral decomposition method for sandstone identification, case study Kutai Basin, Eastern Kalimantan

Seismic reflection is a method commonly used to map hydrocarbons. The reservoir can be characterized using the inversion method by converting the seismic data into acoustic impedance values of rock and spectral decomposition methods are used to delineate low-frequency shadow beneath reservoir caused by the presence of hydrocarbon. The combination of these two methods is used to distribute the hydrocarbon reservoir in the target zone. The inversion used in this research is a model-based inversion, while the spectral decomposition method used is continuous wavelet transform. The result of this study shows that reservoir distribution with low acoustic impedance located at inline 1583, inline 1290, inline 1360, inline 1399. Three of four inline show by spectral decomposition result delineating low-frequency shadow at inline 1290, inline 1360 dan inline 1399, while inline 1583 produces high-frequency anomaly. This phenomenon could occur due to the effect of reservoir thickness that is less than 1/4λ. The reservoir has an acoustic impedance value of 18000-19000 ft.g/s.cc and low-frequency shadow beneath reservoir has 20 Hz frequency indicating the presence of hydrocarbon, while inline 1583 shows high-frequency anomaly 60 Hz this phenomenon shows that the reservoir thickness is thin or less than 1/4λ and indicates of containing gas fluid.