Near-Surface Attenuation Estimation of P and S Waves from Middle East Data
Seismic waves propagating through the Earth are attenuated by conversion of a fraction of the elastic energy to heat. In seismic studies, attenuation provides more information about rock properties than available from seismic velocities alone. This is particularly important for the characterization and monitoring of hydrocarbon reservoirs because attenuation affects both the amplitude and the phase of the seismic data. In laboratory, as well as field measurements, accurate estimation of attenuation is difficult since seismic amplitudes are not only affected by intrinsic damping, but also by other mechanisms such as geometrical spreading, reflections, refractions, scattering and topography. These effects should be accounted for if we want to measure the true intrinsic attenuation. Current attenuation-estimation methods lack accuracy and rarely use the complete seismogram for recovering attenuation properties. To improve this situation, we developed a method to recover the near-surface attenuation properties for realistic geological settings. The method was based on visco-acoustic wave-propagation modelling and included the influence of the source wavelet and the presence of significant surface topography. The technique provided an acceptable result when applied to a data set recorded in the Middle East. Here, we extend the method to the visco-elastic case. Numerical simulations and measurements on field data demonstrate its effectiveness.
AAPG Search and Discovery Article #90077©2008 GEO 2008 Middle East Conference and Exhibition, Manama, Bahrain