Reduction of Tool Mode and Drilling Noise In Acoustic LWD

摘要

A downhole measurement tool includes at least one regular receiver and at least one reference receiver externally deployed on a tool body. The reference receiver is configured to be acoustically isolated from the borehole, for example, via an isolation structure including a high-impedance cap and a low-impedance gap. The reference receiver may be deployed in a linear array with the regular receiver(s) and may be substantially identical to the regular receiver(s) such that it has substantially the same sensitivity to tool mode signals and internal drilling noise as do the regular receivers. Received waveforms may be processed so as to remove tool mode arrivals and/or drilling noise.