|
| | Abstract | | Although seismic attenuation has been widely used to estimate physical conditions and rock properties in various fields, attenuation estimates are currently not routinely derived because of many factors including difficulties of data processing. There are various factors affecting the uncertainties of attenuation estimates such as borehole irregularity, windowing effect, source-formation coupling, seismic scattering caused by heterogeneity of the formation. We investigated and compared the stability of different existing and partly modified attenuation estimation methods by application to both synthetic and actual field sonic logging waveform data. We have found that the quality of inverted attenuation results derived from the spectral method is very low compared to other methods based on median frequency shift method, the number of receiver pairs used for attenuation estimation can be optimized, which is subject to the quality of observed sonic waveform data, optimum receiver-receiver separation distances is required for a stable and accurate measurement. Furthermore, we characterized 1-D heterogeneity of the formation using the velocity logging data to investigate the extent of the seismic scattering effect. Although the calculated spatial autocorrelation functions using the velocity logging data shows that the scattering effect can be neglected, we emphasize that the spatial sampling of the velocity logging data at every 0.15 m is not small enough to characterize heterogeneity and that a study to obtain more highly dense sampling is needed. |
|
|
|
| |
|