| 摘要 |
<p>The present invention offers methods and apparatus for sonic borehole logging of formation shear using discrete frequency measurements. A multipole source transducer (16) emits sonic energy at a location in a borehole (14) of at least one discrete frequency which induces propagation of multipole sonic waves in the borehole: sonic energy of the multipole sonic waves is detected at multiple receiver locations in the borehole by multipole receivers (20, 22, 24 and 26) to produce a received sonic signal for each location, the multiple receiver locations being spaced apart from one another and from the source transducer (16) location. For each receiver location, the complex values of the received sonic signal are detected relative to a predetermined phase reference. The detected complex values of the received sonic signal may be processed to determine multipole sonic wave velocity and shear attenuation at discrete frequencies and to calculate velocity and attenuation as a function of frequency.</p> |
