Relating acoustic wave velocities to formation mechanical properties

Abstract

Proper correlation between formation mechanical properties and acoustic data is essential for acquiring field rock mechanical data for analysis, and it has thereby a great significance to oilfield development.This thesis presents results from a correlation study between formation mechanical properties and acoustic wave velocities from a set of unpublished rock mechanical experiments on sandstone samples from the Norwegian shelf. The core samples from the Norwegian shelf were subjected to triaxial compression tests performed at various confining pressures with simultaneous measurements of acoustic velocities. Correlations between formation compressive strength, elastic stiffness and Poisson's ratio and compressional and shear transit time have been established.The results obtained in this study confirm that the stress level and the stress configuration affect the acoustic velocities, and this should be accounted for when using generalized empirical correlations to estimate formation strength, elastic stiffness and Poisson's ratio from acoustic logs in field studies. The empirical correlations established through this work are found to match reasonable well with other published relations. By acoustic logs from field studies, it is found that the empirical correlations overestimate the formation strength and the elastic stiffness.