周期性螺纹连接管结构中声波的频谱特性测试

建立用于测试声波在钻柱信道中传输及衰减特性的试验装置,对由螺纹连接构成的周期性管结构中声波的传播特性进行试验研究,将利用传递矩阵法计算的结果与试验结果进行对比。结果表明:声波在由螺纹连接构成的周期性管结构中传播时,存在衰减及失真较小的通带和衰减及失真较大的阻带,通带与阻带交替分布;随着发射声波频率的升高,通带声波的衰减增加,当频率超过一定值时,声波完全被吸收,即使发射的声波处于通带,亦难于接收;理论计算结果与试验结果前4个通阻带吻合较好,之后差异明显。这表明理论计算方法在计算低频通阻带分布时具有良好的适用性与计算精度,在此范围内,可以用于钻柱结构内声波传播频谱特性的分析及信息载波频率的选择。

Spectrum characteristics testing of acoustic propagation in drill-string with periodic thread connections

A testing equipment to study the transmission and attenuation behavior of acoustic waves in drill-string was designed, and the propagation characteristics of the acoustic waves in a periodic-thread-connection structure were studied. The experimental results were analyzed and compared with that calculated using a transfer matrix method. The results show that there exists a pass-band with smaller attenuation and distortion and a stop-band with bigger attenuation and distortion when acoustic waves propagate in the drill-string with periodic-thread-connections. The pass-band and stop-band appear alternatively in frequency and their difference reduces with the increase of acoustic frequency. When the frequency exceeds a certain value, the pass-band disappears, which means that the acoustic wave can be completely absorbed. The calculated four lowest-frequency pass-bands and stop-bands agree well with the experimental results, but there after their difference is greater for higher frequency. This shows that the theoretical method works well in the calculation of low-frequency pass-band and stop-band distribution, and can be used to analyze the characteristics of acoustic wave propagation in drill-string and to select proper frequency as an acoustic-information carrier in low frequency range.