Earth acts as a low pass filter. The attenuation of the seismic energy caused by the Earth filter happens because higher frequencies are absorbed more rapidly than lower frequencies resulting in narrowing the frequency spectrum with depth. The narrow frequency bands with a low dominant frequency seismic data always have a coarse vertical resolution, such that the overlapping reflections interfere in one seismic event, which makes it difficult to identify the exact reflection boundary. Enhancing the vertical resolution is important to understand and characterize pay zones in complex structural and stratigraphic settings. However, the enhancement of higher frequencies, usually, leads to an increase in noise levels.
In this paper, we attempted to increase the vertical resolution and maintain the noise at an acceptable level. We aimed to improve the vertical resolution particularly in areas of great economic potential where dominant frequencies in seismic data do not even reach 15 Hz. The dataset used here is from the 3D deep marine survey, in offshore Nile Delta. The interval of interest includes lower-Pliocene turbidite channels and sand sheets, and Messinian clastic-carbonates setup. The Messinian gas sand below the Anhydrite was proved in the area, but have never been followed up as the carbonates/evaporates absorb the seismic high frequency and hide the Messinian thin channels.
Different enhancing-frequency techniques were implemented, keeping in mind maintaining the polarity, and character of the original post stacked volume. Each method has its pros and cons. After application on the 3D seismic data, the frequency bandwidth has been increased by about 10 Hz which allowed the identification of reflections of thin sand layers clearly. Standard validation of frequency enhancement technique is made through correlation with synthetic seismograms obtained from well log data. Synthetic traces proved the validity of the used methods. The minimum resolvable thickness decreased and the ability to delineate the thin-reservoirs improved significantly.
