GEOMETRICAL FACTORS IN SONIC LOGGING

Publisher Website
Google Scholar
Abstract
The purpose of the sonic log is to measure formation velocity, but various geometrical factors can cause apparent velocity readings substantially different from the true velocity at the depth of measurement. An understanding of these factors enables one to derive greater value from the log. Bed thickness, hole size, caves, alteration of the formation adjacent to the bore, spacing of the transducer, and whether the tool is centered in the bore, are among the factors influencing the log. Centering the tool can increase the signal strength, but in large holes and slow formations the first arrival may come through the mud. The transmitter‐receiver spacing which is needed to avoid this is given for various hole sizes and formation velocities. The effect of caves is shown with theoretical and actual curves. There is some evidence that action of the mud or stress concentration around the bore can alter the velocity of the formation; the effect on the indicated velocity is shown as a function of transducer spacing and of degree and depth of velocity alteration.

This publication has 0 references indexed in Scilit: