Comparison Of Log And Laboratory Measured P-Wave And S-Wave Velocities

Longitudinal (p-wave) velocity, shear (s-wave) velocity, and density measurements were made in the laboratory under simulated in situ conditions, on Devonian shale core samples. These values and calculated elastic moduli are compared with data obtained from wire-line logs. The densities and p-wave velocities are in good agreement; however, the laboratory s-wave velocities are consistently higher (10 to 14 percent) than the log measurements. These discrepancies are greatly magnified in the derived elastic moduli. Hypothesizing that the log detected s-wave is in reality the Rayleigh wave, the calculated s-wave velocities agree as well as the p-wave velocities with the corresponding lab measured values.