A MULTI-MODES COUPLING RECEIVER FOR ACOUSTIC LOGGING WHILE DRILLING

Acoustic logging while drilling (LWD) technology plays a more and more important role in highly deviated angle and horizontal well logging due to the advantages such as high efficiency, low cost and etc. However, there still exist bottleneck problems because of the acoustic LWD environment in the borehole including noise of mud and drilling bit and even tool mode waves. Flexural vibration transducers with a small volume and low resonant frequency is a good option in acoustic logging tools. We presented a Helmholtz resonator receiver with multi-modes coupling with wide frequency band, high sensitivity and flat sensitivity curves than receivers with pure bending mode. The finite element method was used to calculate the vibration, admittance characteristics and receiving sensitivities. Considering variables such as geometric sizes in the simulation progress, optimized receiving sensitivity curve was finally obtained, with a maximum value of -195dB, and a fluctuation within +/- 5dB in the range of 10 to 20 kHz. It is appropriate for receiving monopole waves on acoustic LWD tools.