Seismic Attenuation from VSP and Well Log Data: Approaches, Problems and Relative Contribution of Scattering

Abstract

All methods for quantitative interpretation of seismic data are based on the analysis of amplitudes of seismic (reflected) waves. Seismic attenuation along the ray path of a wave significantly affects this amplitude information. As such, understanding of this phenomenon has a huge impact for the industry. For the last sixty years vertical seismic profiling (VSP) was an obvious method of choice for exploring this phenomenon in-situ. A large number of different approaches for attenuation estimation were introduced. We have tested a large number of these methods and developed a reasonably robust workflow for attenuation estimation based on the modified centroid frequency shift method. Seismic attenuation measured from seismic data (so-called apparent attenuation) comprises two different components, namely, transfer of the energy into heat (absorption) and scattering. We employ seismic modelling using finely layered model of the medium obtained from the log data as a part of the workflow to estimate relative contribution of scattering. In order to investigate causes and mechanisms of seismic attenuation we select~70 wells from several areas in Australia (primarily from NW Shelf) with publically-available high-quality well log, VSP data and geological information. In this presentation we show some preliminary results from this study.