Effects of Rock Porosity on Acoustic Wave Velocities Estimation from Sonic Logs

Abstract

Estimation of S-wave velocity from P-wave velocity has been widely used in geomechanical applications as both velocity measurements are not always available. In present study, some of previously suggested equations for estimation of shear velocity have been presented. These equations have local validity and new calibration of constants is needed if used in new region. On the other hand, theoretical background in geomechanics shows linear relationship between the squares of these velocities. Measured data points were tested in this linear equation and it was found that good matching is observed only in clean sandstone samples. The idea that alteration in linearity is mainly due to porosity effect, motivated the authors to make a new regression considering porosity as one of input parameters. The results highly confirmed this method and new correlations with previously published data showed correlation coefficient nearly equal to unity.