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US 8,976,625 B2Granted
Optimization approach to Q-factor estimation from VSP data
AssigneeBaker Hughes Incorporated
InventorEmanouil Blias
Life of this patent
Estimating the term…
Abstract
A zero-offset VSP survey is carried out with spaced apart receivers located in a vertical wellbore. Spectra of the signals at the receivers following wavefield separation are estimated. An absorption coefficient is estimated using differences in spectra between all pairs of receivers.
Claims14
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.
2 more elements
A system configured to evaluate an earth formation, the system comprising:
- a plurality of seismic detectors, each positioned at a plurality of spaced apart locations in a wellbore, configured to acquire seismic data comprising a signal responsive to activation of a seismic source near a top of the wellbore;
- and
- at least one processor configured to:
- estimate a spectrum of the acquired signal 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;
- estimate 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
- evaluate 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.
4 more elements
A non-transitory computer-readable medium product having stored thereon instructions that when read by at least one processor cause the at least one processor to execute a method, the method comprising:
- using seismic data acquired by 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 for 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.
1 more element
Dependencies are inferred from the claim text.