A novel method for separating intrinsic and scattering attenuation for zero-offset vertical seismic profiling data

Summary Intrinsic attenuation has the potential to clarify the physical properties of earth materials, whereas positive utilization of seismic scattering has been recognized as useful in investigating the heterogeneities thereof. However, it has not been easy to separate between intrinsic attenuation and scattering effects. The zero-offset vertical seismic profiling (VSP) survey is recognized to be ideal for attenuation estimation because the VSP survey observes direct waveforms propagating through subsurface formations. The most popular method of separating intrinsic and scattering attenuation generates numerical zero-offset VSP data from known velocity data, such as sonic velocity logs, and isolates the intrinsic attenuation by subtracting the synthetic scattering attenuation from the total attenuation. Numerical experiments have demonstrated the limitation of this conventional method due to its assumption that the intrinsic and scattering attenuation are independent each other. We should take into account the mutual interactions between the intrinsic and scattering attenuation. In order to overcome this limitation, we herein propose a novel method for separating intrinsic and scattering attenuation for zero-offset VSP data by reforming the modified median frequency shift (MMFS) method with seismic interferometry (SI) under the assumption that intrinsic and scattering attenuation are frequency independent and frequency dependent, respectively. The proposed method can simultaneously derive both intrinsic and scattering attenuation estimates from only VSP data without sonic and density well-log data. The numerical experiments of the present study also investigate the importance of parameter optimization in applying pre-processing filters in order to balance the resolving power and noise reduction effect. Finally, we apply the proposed method to zero-offset VSP data acquired in an onshore Abu Dhabi oil field in order to demonstrate the applicability of the proposed method in investigating heterogeneities of subsurface formations and discuss its limitations.