Inelastic attenuation, quantified by Q, the seismic quality factor, has considerable impact on surface seismic reflection data. A new method for interval Q-factor estimation using near-offset VSP data was based on an objective function minimization measuring the difference between cumulative Q estimates and those calculated through interval Qs. To calculate interval Q, we used all receiver pairs that provided reasonable Q values. To estimate Q between two receiver levels, we used the equation that links amplitudes at different levels and could provide more accurate Q values than the spectral-ratio method. To improve interval Q estimates, which rely on traveltimes, we used a high-accuracy approach in the frequency domain to determine time shifts. Application of this method to real data demonstrated reasonable correspondence between Q estimates and log data.

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