SEPARATING INTRINSIC FROM SCATTERING SEISMIC WAVE ATTENUATION FROM FULL WAVEFORM SONIC LOGS IN A GEOTHERMAL FIELD

Abstract

Elastic waves attenuate in the earth due to scattering and absorption. The latter can be linked to fluid movement and is of the utmost importance to the production of a geothermal field. However, it is hard to separate scattering from intrinsic attenuation. Our approach is to use the full elastic waveform from borehole sonic logging, which consists of a coherent part, and incoherent signal produced by the scattered waves (coda). Based on the radiative transfer theory, the coherent energy is affected by the elastic wave attenuation due to both scattering and intrinsic attenuation, while scattering can provide a gain term in the incoherent energy. Here, we quantitatively analyze these intensities to independently estimate the quality factor due to scattering and absorption from full waveform sonic logs in a geothermal field.