Combination of seismic inversion and spectral decomposition to identify reservoir and gas content: A case study of CH field, East Java Basin

Seismic inversion and spectral decomposition has been carried out to identify reservoir and gas content in CH field East Java Basin. The combination of this geophysical methods is intended to identify gas reservoir. This study aims to delineate identify the reservoir based on seismic inversion result and determine the gas content based on the spectral decomposition. Seismic inversion is carried out by using model-based inversion, which is giving more plausible result by using forward modelling concept to calculate the synthetic seismic as the part of inversion algorithm. The spectral decomposition is performed by using continues wavelet transform (CWT) because this method provide the high resolution in time and frequency domain. This method applied into 7 Hz and 20 Hz frequency to determine the low frequency anomaly. Model based seismic inversion result show that the reservoir zone is clearly identified, with acoustic impedance below 11,000 ft.g/s.cc. The reservoir shows circular geometry based on the sub surface geological condition of carbonate buildup. The time frequency analysis is carried out in the frequency of 7 Hz and 20 Hz. The result shows low frequency high amplitude anomaly at the frequency of 7 Hz. The low frequency anomaly is located in the area, which is indicated by low acoustic impedance from the seismic inversion result. Combination of these two methods resulting the satisfactory identification methods, which is applicable in the gas reservoir identification.