气体钻井钻柱内声波信号传输规律分析

针对气体钻井随钻测量问题，参照医用听诊器的工作原理，提出在气体钻井中利用钻柱内声波进行井下信息传输的方法；通过建立钻柱内声波传播的数学模型并求解，得出钻柱内声波信号传输的衰减规律；利用声波导理论对钻柱的声波导特性进行分析，计算钻柱内声波的截止频率。通过管道声波传输实验，将采集声波信号与计算结果进行比对，验证了理论分析的准确性。结果表明，气体钻井钻柱内声波信号传输过程中的衰减程度随频率的升高而逐渐加剧；钻柱的内径尺寸决定了内部各阶声波的截止频率，内径越大，声波的截止频率越低；声波信号传输载波频率的选择时，应兼顾钻柱内声波信号的衰减规律和不同尺寸钻具的声波导特性，尽量选择钻柱截止频率内较低的频段，减少因高次波激发造成的衰减，延长声波信号的传输距离。

Analysis of Internal Acoustic Signal Transmission in Gas Drilling Strings

Concerning the problem of gas drilling measurement, a method for gas drilling using internal acoustic signal transmission in a gas drilling string was proposed with reference to the working principle of a medical stethoscope. By constructing a mathematical model and determining the solution for the sound wave propagation in the gas drilling string, the pattern of the acoustic signal transmission attenuation was derived. The waveguide characteristics of the gas drilling string were analyzed using acoustic theory, and the cutoff frequency of the sound waves in the gas drilling string was calculated. Through pipeline acoustic transmission experiments, the collected acoustic signals were compared with the calculated results to verify the accuracy of the theoretical analysis. The results showed that the degree of attenuation during the internal acoustic signal transmission in the gas drilling strings gradually intensified as the frequency increased. The inner diameter of the gas drilling string determined the cutoff frequency of the sound waves in each internal segment, with larger inner diameters resulting in lower cutoff frequencies. When selecting acoustic signal transmission carrier frequencies, care should be taken to select the cutoff frequencies of the gas drilling string as low as possible according to the pattern of the attenuation of the internal acoustic signals in the gas drilling strings and the waveguide characteristics of drilling strings with different sizes, to reduce the attenuation caused by the higher-order shock waves and extend the transmission distance of the acoustic signals.