Ground Roll and Random Noise Attenuation Using Common Offset Common Reflection Surface Stacking

Seismic noise can be divided to random and coherent in reflection survey. The ground roll is a coherent noise in land seismic data that has high energy, high amplitude, low frequency and low velocity. It usually masks the reflections. Therefore, it must be attenuated in the seismic data processing. In this paper, we proposed a modification on the common offset common reflection surface method to attenuate ground roll and random noise. The CO CRS stacking operator is a hyperbola; therefore, it fits the hyperbolic reflections in the prestack data. Ground roll and random noise has linear and uncorrelated traveltime respectively. When the CO CRS operator is applied to the data, the reflection events can be detected by the coherency analyses. High coherency values belong to the reflection events, and low values indicate that no events with hyperbolic traveltime are detected. As a result, when the events are distinguished, any event with non-hyperbolic traveltime can be muted. We applied the proposed method on two real land data sets. The new method was compared with the f-k filtering and conventional CO CRS stacking after the f-k filtering. Results showed that the proposed method attenuated aliased ground roll better than the f-k filtering and conventional CRS. Further investigation was the effect of reflection amplitudes on ground roll attenuation by the CO CRS stacking. For a better attenuation, the minimum coherency of reflections had to be higher than the maximum coherency of the ground roll. Therefore, the intersection of the minimum reflections coherency and the maximum ground roll coherency is an SNR threshold (dB) for ground roll attenuation with FO CRS stacking.