An equivalent-tool theory for acoustic logging and applications

• Published in: Applied geophysics 2011-03, Vol.8 (1), p.69-78
• Main Authors: Su, Yuan-Da, Tang, Xiao-Ming, Hei, Chuang, Zhuang, Chun-Xi
• Format: Article
• Language: English
• Subjects: Acoustic impedance; Acoustics; Boreholes; Data processing; Dispersions; Drilling; Earth and Environmental Science; Earth Sciences; Equivalence; Geophysics/Geodesy; Geotechnical Engineering & Applied Earth Sciences; Logging; Mathematical models; Theory; Wave power; Wave propagation; 声学特性; 声波测井仪; 工具论; 数据应用; 有线随钻; 现场数据; 等效模型; 随钻测井
• ISSN: 1672-7975; 1993-0658
• DOI: 10.1007/s11770-011-0272-6

The influence of an acoustic logging tool on borehole guided wave propagation should be considered in the processing and inversion of the guided waves for formation acoustic property estimation. This study introduces an equivalent-tool theory that models the tool response using an elastic rod with an effective modulus and applies the theory to multipole acoustic logging for both wireline and logging while drilling （LWD） conditions. The theory can be derived by matching the tool’s acoustic impedance/conductance to that of the multipole acoustic wavefield around the tool, assuming that tool radius is small compared to wavelength. We have validated the effectiveness and accuracy of the theory using numerical modeling and its practicality using field data. In field data applications, one can calibrate the tool parameters by fitting the theoretical dispersion curve to field data without having to consider the actual tool’s structure and composition. We use a dispersion correction example to demonstrate an application of the simple theory to field data processing and the validity of the processing result.