The gamma ray logs from five exploration wells have been used and extrapolated by a 3D seismic data set to obtain the map of sand reservoir distribution in the X field. In order to extrapolate the gamma ray log outside the available wells, an extended elastic impedance (EEI) sections have been used. The EEI sections from a 3D seismic data set were generated because the seismic amplitudes as well as the acoustic impedance sections do not give a good correlation with the gamma ray log in the zone of interest. The EEI sections have proven to be a powerful tool for matching the gamma ray properties and its lithology in the zone of interest. The spectral decomposition method has been exploited to deal with moderate thickness of the sandstone reservoir. The experiment proved that at a peak frequency between 14-16 Hz, the distribution of the reservoir thickness can be followed clearly throughout the field. The reservoir thickness distribution can be enhanced and emphasized by using a specific technique which is referred to as waveform classification which yields a better geometrical image of the sandstone reservoir. This result can be further improved by using binary masking technique.
Author : T. A. Jusri, S. Munadi, S. Winardhi, S. Hidayat, W. Permono