High Frequency Losses – Stripping Various Causes

The quantitative use of the seismic amplitude information during the interpretation is a key point for many prospect evaluations and almost all reservoir characterization studies. The local amplitude information of interest is always affected by a series of signal attenuators along the propagation of the incident and reflected wavefield which are highly dependent upon the geological context, structural shape, lithologies and fluids. Also, incident amplitude effects might or might not have frequency dependence as well as phase or dispersion characteristics. These many causes of attenuation are often pragmatically treated by a combination of a few well-known tools: spherical divergence compensation, surface-consistent or volumic time and frequency-dependent compensations. Cases where severe amplitude attenuation effects cannot be treated using usual approaches are a serious issue, in particular for seismic characterization of reservoirs. In this paper, we present some ways to study the impact and the relevance of specific attenuation processes. Alternative mechanisms and tools for a quantitative assessment of these processes are proposed. Some results are shown from field case studies including VSP data and 3D surface acquisition, standard and broadband. We also attempt to point out the impact of the bandwidth in the identification and quantification of possible attenuation causes.