| 摘要 |
<p>The invention is a method for improving quality of seismic data generated with a source (34) positioned substantially at the lower end of a drill string within a wellbore. A pilot signal is detected at the upper end of the drill string for cross-correlation with signals detected by field sensors (8, 9) positioned at the earth's surface displaced from the wellbore. Noise is reduced in the pilot signal by detecting the noise with a sensor (7) positioned to be sensitive to the noise but substantially insensitive to the acoustic signal transmitted up the drill string from the source. The frequency band within which there is high coherence between the energy in the noise signal and the pilot signal is determined. The noise signal is then amplified by a factor equal to the average ratio of the energy amplitude of the pilot signal to the noise signal within this frequency band, and this weighted noise signal is substracted from the pilot signal to reduce the noise in the pilot signal.</p> |
