Communications – electrical: acoustic wave systems and devices – Seismic prospecting – Well logging
Patent
1989-04-28
1990-08-21
Lobo, Ian J.
Communications, electrical: acoustic wave systems and devices
Seismic prospecting
Well logging
36472401, 367 43, 367 34, G01V 136
Patent
active
049512668
ABSTRACT:
The present invention is directed to filtering out unwanted components contained in acquired sonic well logging data, e.g., reflected wave components, converted wave components, casing arrivals, tool arrivals and/or noise. In the filtering method, the waveform components of each waveform are treated as vectors, each vector having n samples. The vectors, described in n-dimensional space, are rotated to a new coordinate system whose directions, characterized as eigenvectors, are aligned with the primary directions of the wave component vectors. The eigenvectors are ordered such that the first eigenvector represents the wave components' main direction, the second eigenvector represents the wave components' next main direction, et cetera. By projecting the waveform components onto the principal eigenvectors, the reflected wave components, converted wave components and/or noise component of each waveform is substantially eliminated. Methods are also disclosed for approximating the eigenvectors. The present invention is further directed to estimating a reflection coefficient of a bed boundary in the formation, identifying the lithology of the formation traversing the borehole, and compressing the sonic data, based in some manner on the obtained eigenvectors or their approximations.
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Lobo Ian J.
Schlumberger Technology Corporation
Tager Clifford L.
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