Patent ID: 8976625
Filing Date: 2015-03-10
Classification: G01V

Abstract:
1. A method of evaluating an earth formation, the method comprising: acquiring seismic data using a plurality of seismic detectors, each at one of a plurality of spaced apart locations in a wellbore, responsive to activation of a seismic source near a top of the wellbore; estimating a spectrum of a down going wave field of the acquired seismic data at each of the plurality of seismic detectors by separating the down going wave field from an up going wave field of the acquired seismic data; estimating an absorption coefficient of the earth formation for at least one pair of the plurality of seismic detectors by minimizing an objective function based on an exponential relation between the spectra of the at least one pair of seismic detectors; and evaluating the earth formation using the estimated absorption coefficient to indicate at least one of (i) a lithology and (ii) a fluid content of the earth formation.