低频单极随钻声波测井的钻铤波抑制方法研究

Effective suppression of collar waves is crucial for the accurate acquisition of formation information in logging while drilling (LWD). In this work, we propose a novel acoustic isolator for LWD based on phononic crystal theory. The frequency response curves, time domain waveforms and the mechanical properties of the isolator are comprehensively analyzed through the numerical simulations. It is found that the proposed isolator effectively attenuates collar waves within a broad low frequency range without generating converted Stoneley waves. This feature is particularly significant for permeability inversion and related studies that rely on low frequency Stoneley waves. Compared with traditional periodic externally grooved acoustic isolators, the new isolator exhibits excellent mechanical properties. Additionally, a workflow utilizing signal processing techniques for residual collar waves suppression is introduced. The coherence of formation P-wave signals is enhanced significantly and the velocities of P-wave and S-wave of the formation are measured accurately by applying the workflow proposed. This study provides valuable guidance for improving the effectiveness of formation parameters inversion in monopole acoustic LWD.