Attenuation estimation from sonic logging waveforms combining seismic interferometry and common-midpoint approach

Abstract

Although attenuation estimation methods using sonic logging waveforms provide the highest resolution among seismic methods and enable us to characterize in great detail the attenuation properties of subsurface rocks, such attenuation estimation methods are not used routinely, indicating that there is still room for improvement. To further improve the performance of an existing modified median frequency shift (MMFS) method, we have developed a new algorithm by combining seismic interferometry (SI) and the common-midpoint (CMP) approach. Redatuming a transmitter position by applying SI can shorten the transmitter-receiver distance, leading not only to higher depth resolution but also to a lower signal-to-noise ratio (S/N) of the attenuation profiles. To compensate for the decrease in the S/N, we used the redundancy of overlapping receivers at each receiver level in a sonic logging measurement using the multireceiver tool; we improved the S/N by stacking the redatumed sonic logging waveforms. Then, based on the CMP approach, we constructed the workflow to estimate attenuation using redatumed sonic logging waveforms. We applied our method to numerical and real sonic logging waveforms to investigate its applicability in comparison with that of the existing MMFS method in terms of depth resolution and S/N. The results of numerical experiments on noisy data and velocity heterogeneity models demonstrate a trade-off relationship between the depth resolution and stability, which can be controlled by selecting transmitter-receiver pairs. Finally, the application of our method to real sonic logging data demonstrates the advantages in terms of resolution and the disadvantages in stability in comparison with the existing MMFS method. Similar to the numerical results, we found a trade-off relationship between such advantages and disadvantages, which can be controlled by selecting transmitter-receiver pairs.