Nonstationary maximum likelihood method to estimate dispersion spectra for full waveform sonic logging
AssigneeSaudi Arabian Oil Company
InventorsXuekai Sun, Chris B. Ayadiuno
Life of this patent
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Abstract
The present disclosure describes methods and systems for estimating dispersion spectra for full waveform sonic (FWS) logging. One computer-implemented method includes receiving FWS data, performing frequency-spatial (FX) transform on the FWS data, using a nonstationary predictive error filtering (PEF) inversion on the transformed FWS data to estimate local matrix L and matrix P, calculating an inverse covariance matrix based on the estimated local matrix L and matrix P, and obtaining a nonstationary maximum likelihood method (MLM) spectra based on the inverse covariance matrix.
Claims15
A method comprising:
- receiving full waveform sonic (FWS) data, wherein the FWS data are sonic waveforms recorded by a receiver array including M receivers, the sonic waveforms are excited by a transmitter and propagate along a borehole on a hydrocarbon reservoir, and M is an integer greater than 1;
- performing frequency-spatial (FX) transform on the FWS data;
- using a nonstationary predictive error filtering (PEF) inversion, instead of Burg algorithm, on the transformed FWS data to obtain PEF coefficients and corresponding PEF predictive errors;
- estimating local matrix L and matrix P, wherein the estimated local matrix L is formed using the PEF coefficients, and the estimated local matrix P is formed using the corresponding PEF predictive errors;
- calculating an inverse covariance matrix based on the estimated local matrix L and matrix P;
- obtaining a nonstationary maximum likelihood method (MLM) spectra based on the inverse covariance matrix;
- and
- obtaining petrophysical properties near the borehole on the hydrocarbon reservoir based on the nonstationary MLM spectra.
A device comprising:
- a memory;
- and
- a processing unit that is arranged to perform operations including:
- receiving full waveform sonic (FWS) data, wherein the FWS data are sonic waveforms recorded by a receiver array including M receivers, the sonic waveforms are excited by a transmitter and propagate along a borehole on a hydrocarbon reservoir, and M is an integer greater than 1;
- performing frequency-spatial (FX) transform on the FWS data;
- using a nonstationary predictive error filtering (PEF) inversion, instead of Burg algorithm, on the transformed FWS data to obtain PEF coefficients and corresponding PEF predictive errors;
- estimating local matrix L and matrix P, wherein the estimated local matrix L is formed using the PEF coefficients, and the estimated local matrix P is formed using the corresponding PEF predictive errors;
- calculating an inverse covariance matrix based on the estimated local matrix L and matrix P;
- obtaining a nonstationary maximum likelihood method (MLM) spectra based on the inverse covariance matrix;
- and
- obtaining petrophysical properties near the borehole on the hydrocarbon reservoir based on the nonstationary MLM spectra.
A non-transitory computer-readable medium storing instructions executable by a computer system to perform operations comprising:
- receiving full waveform sonic (FWS) data, wherein the FWS data are sonic waveforms recorded by a receiver array including M receivers, the sonic waveforms are excited by a transmitter and propagate along a borehole on a hydrocarbon reservoir, and M is an integer greater than 1;
- performing frequency-spatial (FX) transform on the FWS data;
- using a nonstationary predictive error filtering (PEF) inversion, instead of Burg algorithm, on the transformed FWS data to obtain PEF coefficients and corresponding PEF predictive errors;
- estimating local matrix L and matrix P, wherein the estimated local matrix L is formed using the PEF coefficients, and the estimated local matrix P is formed using the corresponding PEF predictive errors;
- calculating an inverse covariance matrix based on the estimated local matrix L and matrix P;
- obtaining a nonstationary maximum likelihood method (MLM) spectra based on the inverse covariance matrix;
- and
- obtaining petrophysical properties near the borehole on the hydrocarbon reservoir based on the nonstationary MLM spectra.
Dependencies are inferred from the claim text.