EFFECT OF BOUNDARY CONDITIONS ON RECEIVING TRANSDUCER FOR LWD MULTIPOLE ACOUSTIC LOGGING TOOL

摘要

The receiving transducer is a key element of the LWD multipole acoustic logging tool, and its performance directly affects the signal quality. The effects of boundary conditions, metal substrate thickness and sealing way on the vibration mode and receiving sensitivity are analyzed by finite element method. The simulation results show that the clamped boundary condition at both ends is the most suitable mechanical installation way, because receiving sensitivity is most gentle, undulation is the smallest, receiving sensitivity is relatively high in this condition. The thickness of intermediate metal substrate has a certain influence on the receiving sensitivity. The receiving sensitivity slightly rises with the increase of the metal substrate thickness, and the sensitivity jump point near the frequency of 3 kHz moves to the high frequency. If the receiving transducer is sealed with cuboid shell in silicone oil, the sensitivity curve jumps at multiple frequency points, and the fluctuation becomes large in the working frequency. The numerical simulation results have a good guiding effect on the design, fabrication and correct installation of the transducers.