Thomas J. Blankinship

A Dipole Array Sonic Tool for Vertical and Deviated Wells

Dipole-array sonic tools are well-suited for estimating acoustic shear-wave velocities in soft, unconsolidated, slow formations. Dipole sources induce flexural waves that are sustained in such formations. One of the main challenges of dipole sonic logging has been to descend into deviated wells. In deviated wells, the tool body must withstand compressive forces but, for a dipole tool, a rigid tool body conveys a strong direct arrival that interferes with the flexural mode. ○ A new semirigid-tool design enables logging with both dipole and monopole sonic tools in deviated wells. ○ The dipole acoustic source has a broad bandwidth, extending down to the 600-Hz range, that is low enough to excite large boreholes and very slow formations.