Caliper Effect on Borehole Coupling
The mechanism of low-frequency Borehole Coupling from the literature is here applied to a borehole of non-uniform radius. It is noted that in addition to the pressure signal in a fluid-filled borehole coincident with the passage of an external plane compressional wave, there are waves created at any change in radius which arrive later as coherent noise. This is illustrated first with a single step-change in radius. An example using the caliper log from an oil well shows that these delayed waves create a noise train of substantial amplitude relative to the direct compressional wave. It is pointed out that a down-hole pressure source will radiate a noise train due to caliper changes which will follow the direct compressional wave with exactly the same waveform as that encountered in Borehole Coupling.
Figures & Tables
Seismic Wave Propagation: Collected Works of J. E. White
This first chapter sets the stage for the later technical development of Dr. Whit’s career in applied seismics. Experiments, f’wst at the Acoustics Laboratory of the Massachusetts Institute of Technology and later at Mobil Oil and Marathon Oil, provided insight into the general problems of impedance measurements, transduction, filtering, and attenuation. These papers also serve as a bridge to show geophysicists how theft own experiments in seismology naturally interface with (indeed, arose out of) the larger world of sound measurements in air and water. These experiments demonstrate the power of geometrically constrained experiments to allow verification of approximate (and in some cases, exact) theories of sound.