Reservoir Delineation Using Bandwidth Extension and Phase Decomposition

Sandstone reservoir units prevalent in an upper slope Niger Delta oil field are commonly below seismic temporal resolution. Although conventional seismic amplitude and amplitude-variation-with-offset are good indicators of oil-filled reservoir rock in this area, they do not necessarily show the vertical distribution of reservoir and may sometimes be suppressed for thin pay intervals.
In some cases, multiple sub-tuning reservoir sands appear as one event on the original seismic data and derived attributes. Bandwidth extension using sparse-layer inversion better resolves thin layers than does the original seismic data and can detect multiple interfaces that are not otherwise seismically separated. As the hydrocarbon-filled reservoirs are low impedance relative to the surrounding shales, phase decomposition enhances amplitude anomalies and is found to have improved correlation between seismic amplitude and presence or absence of hydrocarbons. Combining bandwidth extension and phase decomposition improves determination of the internal architecture of pay intervals as sub-tuning vertical variations in impedance become more apparent as are lateral changes in thickness. Resulting amplitude maps are sharper and provide better delineation of the areal reservoir distribution of reservoir as evidenced by well ties.