The source of this ringing, which is not excited by the first arriving energy, is not now known with certainty, but may be a package resonance excited by tube waves. Whether in the casing, in the production string, or in the microtool access, coupling of the packages to the formation qualitatively appears to be good. Vertical component output for incoming signals at horizontal incidence for the SHGP, cemented-in geophones and microgeophone tools. 400 msec total time. Corresponding icons represent acquisition geometry.
Open circles represent casing or tubing.
Solid circle and bar represent borehole package and locking mechanism. Vertical component output for incoming signals at 30 degree incidence for the SHGP, cemented-in geophones and microgeophone tools. 100 msec total time. Signal and noise spectra for the cemented-in geophone and the microgeophone package. Both signals and their respective, corresponding noise spectra are normalized by the peak amplitude of the signal spectra.