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20多年来,所谓声波测井一直指的是利用双接收器下井仪检测首至波幅的压缩波声速测井。今天,声波测井技术能够利用声波形中包含的更多的声信息来获得切变波和斯通利波的速度以及幅度衰减特性。这需要使用能进行全波分析的信号处理技术。这种技术与标准的双接收器下井仪处理技术相比,通常需要对波场进行更多的空间抽样。为达到这一要求,我们设计了一种新型多接收器声波下井仪。 本文介绍一种新型声基阵下井仪,其基阵有8个接收器,接收器间隔为6英寸,基阵与两个发射器中较近者的距离为8英尺。本下井仪除增加了基阵检测能力之外,标准短源距和长源距声波测井是现有的。其中还加进了一个能够测量泥浆速度的特殊部分。井下电子装置能给出数字化波形采集,其有效分辨力为11位。 为了能从全波形中提取辅助信息,现已开发了一种慢度--时间相干(STC-slowness—time coherence)处理方法。STC处理根据相似技术可识别出通过基阵的相干到达信号。最后给出了由裸眼井和套管井得到的波形实例和经过处理的测井记录的例子,说明了本下井仪的性能。
For more than two decades, so-called sonic logging has been referring to the use of dual-receiver downhole tools to detect first-to-amplitude compression-wave velocity logs. Today, acoustic logging technology uses the more acoustic information contained in the acoustic waveform to obtain the velocity and amplitude attenuation characteristics of shear and Stoneley waves. This requires the use of signal processing techniques that enable full-wave analysis. This technique typically requires more spatial sampling of the wavefield than standard dual receiver downhole processing techniques. To meet this requirement, we designed a new multi-receiver sonic wave downhole instrument. This article describes a new acoustic-based subsurface injector with an array of 8 receivers spaced 6 inches apart and the array being 8 feet closer to the nearest of the two transmitters. In addition to increasing the downhole instrument to increase the detection capability of the array, the standard short source and long source from the acoustic logging is existing. It also includes a special section that measures the velocity of the mud. Downhole electronic devices can give digital waveform acquisition, the effective resolution of 11 bits. In order to extract the side information from the full waveform, a method of dealing with STC-slowness-time coherence has been developed. The STC process can identify coherent arrival signals through the array based on similar techniques. Finally, examples of waveforms obtained from open-hole and cased-hole wells and examples of processed log records are given to illustrate the performance of the downhole tool.