Application of spectral inversion to enhance seismic resolution in Nam Con Son basin, offshore Vietnam

Applications of spectral inversion on a seismic dataset in Nam Con Son basin, Vietnam, have successfully resolved the wavelet interferences created by complex reflectivity patterns of the inter-bedded sand bodies with thin claystones and coal layers. Bandpass filtering was performed to examine different frequency bands of the inverted data for useable signal and lateral coherence. The desired bandwidth for spectral inversion result was 10-100 Hz, almost twice the original bandwidth of 20-65 Hz. Vertical resolution in the reservoir level was increased from 25 m to 15 m. The additional reflections that have resulted from the enhanced frequency content are found to be highly correlated with well logs with an average coefficient of 0.7. Furthermore wavelet deconvolution was applied to improve vertical resolution to 13 m and succeeded in bringing the seismic reflections closer to the earth reflectivity. Several apparent discontinuities due to wavelet interferences were revealed as continuous geological features by the inversion process. The tops and bases of particular sandstones with thickness greater than 13 m are now resolved and can be interpreted individually, allowing thickness estimation of the reservoir. The main fault systems that were defined from the original seismic data are consistent with the high-resolution data, while additional small faults, with displacements of about 16 m, have become visible in the central fault block, potentially separating the reservoir sand bodies into smaller units.