Communications – electrical: acoustic wave systems and devices – Seismic prospecting – Well logging
Patent
1990-10-09
1991-10-15
Lobo, Ian J.
Communications, electrical: acoustic wave systems and devices
Seismic prospecting
Well logging
367 34, 73151, G01V 140
Patent
active
050580779
ABSTRACT:
The technique according to the present invention is useful for generating a corrected well log which otherwise would include erroneous signals from downhole sensor. Such signal error may be caused, for example, by periodic movement of the drill collar axis with respect to the borehole axis, eccentric rotation of the drill collar with respect to the borehole, or a whirling or precessing of the drill collar in the borehole. According to the technique of the present invention, these sensor signals are generated at time intervals of less than one-half the period of the highest frequency of the periodic movement. Discrete sensor signals are averaged to generate an average sensor signal as a function of borehole depth. Discrete sensor signals are also recorded to generate a time-varying sensor signal profile, the magnitude of frequency components of the time-varying sensor signal profile is determined, and the average sensor signal is corrected as a function of the determined magnitude of the frequency components. The corrected sensor signals are preferably recorded as a function of borehole depth to generate a corrected well log. The system according to the present invention includes sensors, a computer, a signal processor, and a plotter suitable for outputting a corrected well log.
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Baroid Technology Inc.
Lobo Ian J.
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