钻柱中换能器声波信号传输特性实验研究

利用声波通过钻柱传输井下信息,具有得天独厚的信道条件,但是声波在钻柱中的传播特性还没有得到充分的研究,尤其是贴近工程应用的实验研究。依托低频宽带换能器建立了测试声波在钻柱信道中传输的实验装置,基于该装置对换能器声波信号的传输特性进行了实验研究及分析。结果表明:随着换能器激励电压的增大接收信号幅值呈现增大趋势,当电压大于130 V时接收信号幅值趋近饱和。理论和实验分析得到的频域特性均表现出明显的梳状滤波特性;但具体通阻带分布和结构形式存在差异,实际钻柱信道的频域特性更为复杂。由于换能器非线性特性和钻柱信道频带特性共同作用,对于实验用低频宽带换能器,选取3 100 Hz以内频率,并结合正交频分复用编码技术可极大增强声波传输的速率和适用性。

Experimental study on the transmission characteristics of transducer acoustic signal within drill string

The drill string provides advantaged conditions for high-speed acoustic transmission. But the characteristics of acoustic waves transmitting through the drill string have not been adequately studied, especially the experimental studies are rarely carried out and there is no mature approach. Test device for measuring the transmission of acoustic waves in a drill string channel is established by means of a low frequency band transducer. Low frequency band transducer has influence on transmission characteristics are studied and analyzed based on experiments. The results show that the amplitude of the received signal is increasing with the increase of the transducer excitation voltage. The received signal amplitude will express saturation phenomenon when voltage is more than 130V. The characteristic of the frequency domain obtained by both theoretical and experimental analysis is comb filter. However, there are some differences in band structure, and the frequency domain of the actual drill string channel is more complex. Mainly based on experiment, the nonlinear character of low frequency band transducer and drill string channel frequency band have an effect on the received signal. The spectrum variation rules of drill string structure and nonlinear character of low frequency band transducer are analyzed to determine the elemental communication frequency band is 3100Hz using in the acoustic telemetry system based on the drill string.