首页   按字顺浏览 期刊浏览 卷期浏览 Eccentric dipole sources in fluid‐filled boreholes: Numerical and experimental results
Eccentric dipole sources in fluid‐filled boreholes: Numerical and experimental results

 

作者: H. D. Leslie,   C. J. Randall,  

 

期刊: The Journal of the Acoustical Society of America  (AIP Available online 1990)
卷期: Volume 87, issue 6  

页码: 2405-2421

 

ISSN:0001-4966

 

年代: 1990

 

DOI:10.1121/1.399086

 

出版商: Acoustical Society of America

 

关键词: SENSORS;BOREHOLES;WAVE FORMS;ECCENTRICITY;AMPLITUDES

 

数据来源: AIP

 

摘要:

A frequency‐wavenumber (ω−k) representation is given for the response of eccentric multipole sensors in a fluid‐filled borehole. Specializing to eccentric dipole sensors, synthetic time‐domain waveforms from an array of receivers deployed along the axis of the borehole are displayed for a range of eccentricity magnitude and orientation, formation slowness, and borehole radius. Flexural wave slowness estimates within several frequency bands are extracted from the synthetic waveforms using a semblance technique. For eccentricity small relative to the borehole radius, the character of dipole waveforms and the estimated flexural slowness are little changed. When the eccentricity is a substantial fraction of the borehole radius, flexural wave amplitude is greatly increased, and strong nonmonotonic trends are introduced due to interference with other modes. If eccentricity is not parallel to the transmitting dipole axis, substantial signals are detected on cross‐dipole receivers, perpendicular to that of the transmitting dipole. Eccentricity effects decrease with frequency. Even for large eccentricity, flexural slowness estimates are affected only slightly. Scaled laboratory experiments confirm the numerical results. Comparison of the experimental and numerical waveforms is made for both centered and eccentric dipoles in several model formations. The predicted increase and nonmonotonic variation of flexural wave amplitude versus receiver offset for eccentric sensors is observed. Experimental and numerical waveforms overlay with excellent agreement.

 

点击下载:  PDF (1957KB)



返 回