不连续边界因素对周期管结构声传输特性的影响

INFLUENCE OF DISCONTINUOUS BOUNDARIES ON ACOUSTIC TRANSMISSION IN PERIODIC CASCADE WITH APPLICATION TO DRILL PIPES

为实现油气井测试的井下声遥测,提出纵波作为信息传输载体,应用有限单元法求解波动方程,研究钻杆等周期管结构信道的行波传输规律。由时域瞬态响应特性,探讨了通阻带交替、通带非平滑伴有谐振尖峰的梳状滤波器结构及产生机理。分析了端面、管箍截面积、杆长等边界对通阻带分布的影响,以及声换能器在钻杆信道的位置设计和泥浆介质的阻尼影响。力锤脉冲激励的实验结果表明:周期管结构信道存在多重回波、振铃衰落、通阻带交替和偏移等复杂特性,但利用扫频确定最佳载波频率或宽带通讯能够改善传输性能。

Influence of discontinuous boundaries on transient acoustical behavior of peridic drill pipes was analyzed including ends,cross-sectional areas and lengths using a time-domain algorithm based on finite element method.The time-domain numerical method obtained comb filter properies,location and width of pass bands or stop bands and spikes within each pass band.And characteristic and generation mechanism of spikes were presented.The position of acoustic transducers was discused to match acousitically the impedances of the drill pipes to which they were connected,and to reduce reflections and dispersions.The attention was also given to effect of mud.The responses of hammer impulses show that drill pipes as a periodic structure have complex acoustical properties in time and frequency domains.However,the use of the available modelling and singnal processing techniques can make drill pipes as a waveguide for transmitting information.