随钻新型隔声体的声学性能研究*

近年来,随钻声波测井成为了一种新兴的勘探方式,但是在勘探过程中产生的钻铤波会影响地层信号的提取。如何能够更有效的提取地层信号,成为学者研究的重点课题。本文基于声子晶体理论设计了一种新型隔声体,相对于传统刻槽结构能够更好的压制钻铤波。首先基于周期结构理论,利用有限元软件COMSOL MUTIPHYSICS计算了不同刻槽结构的能带图,相比于传统刻槽结构,新型隔声体有更宽的带隙,说明新型刻槽结构可以更有效的阻隔钻铤波。接着在测井模型中对刻槽结构进行频响函数曲线的计算,验证了新型刻槽结构隔声效果在所计算频率范围内优于传统刻槽结构。然后分析了在能带计算和频响曲线计算下隔声效果最好的声源频率(17kHz和22kHz)时新型刻槽结构的STC(时间慢度相关法)处理对比,最后对比声源频率17kHz下新型刻槽结构和传统刻槽结构的STC信号处理,发现此声源频率时新型刻槽结构可以更好的提取地层折射纵波和横波。

Acoustic performance study of new sound insulation body in logging while drilling

Logging while drilling has become an emerging exploration method. The collar waves generated during the exploration process can affect the extraction of formation signals. How to extract the formation signal more effectively has become a key research topic for scholars. In this paper, a new type of sound isolator is designed based on phononic crystal theory, which can better suppress the collar waves compared with the traditional grooved structure. Firstly, based on the periodic structure theory, the band diagrams of different grooved structures were calculated by using the finite element software COMSOL MUTIPHYSICS. The new sound isolator has a wider band gap compared with the traditional grooved structure, which indicates that the new grooved structure can block the collar waves more effectively. Then, the frequency response function curve of the grooved structure was calculated in the logging model, and it was verified that the sound insulation effect of the new grooved structure was better than that of the traditional grooved structure in the calculated frequency range. Then we analyzed the STC (slowness time cohernce) processing of the new grooved structure at the source frequencies (17 kHz and 22 kHz) with the best sound insulation effect under the band calculation and frequency response curve calculation. We finally compared the STC signal processing of the new grooved structure and the conventional grooved structure at the source frequency of 17 kHz. It is found that the new grooved structure could better extract the ground refraction longitudinal and transverse waves at the source frequency.