Abstract:
Tuning analysis for thin beds using Amplitude Variation with Offset (AVO) and
spectral decomposition have been carried out in a field, offshore Niger DeltaGamma
ray and resistivity logs were used for lithology and fluid identification. Well-to-seismic
tie was generated from sonic and density logs. AVO was carried out using partial stacks
of near, mid and far angles. This was done using Hampson Russell software version
10.2. Spectral decomposition analysis was done using the fast fourier transform
method. The stratigraphy is alteration of sand and shale lithologies. The delineated
reservoirs lie within a depth interval of 1,800 3,640 m subsea. Crossplots of logs and
seismic data reveal gas, oil, water, sand and background of shale. Also, shallow gas
sands were mapped at shallow depths. Analysis from gradient and intercept crossplots
revealed a class III AVO gas sand. Compressional and shear wave impedance maps and
sections derived from the inversion process predicted the lateral extent of reservoirs
and also aided in fluids and lithology discrimination. Spectral decomposition and
inversion resolved thin beds that were not mapped from seismic data. The beds were
beyond the resolution of seismic data and located at a depth interval of 2,180 2,545
m subsea.
