Rock Properties Interpreted from Sonic Velocity Logs

A comparison of sonic velocities obtained by geophysical logging methods with core values of porosity, static Young's modulus, and ultimate strength indicates that relationships exist between these properties over a wide range of volcanic rocks penetrated in a series of drill holes in Alaska. The velocity-porosity equation of Wyllie is shown to be applicable to these rocks, and is essentially independent of rock type. A Young's modulus-velocity relationship is also demonstrated for these rocks with a minor dependency on rock type. The relationship between velocity and ultimate strength, however, is shown to be more strongly dependent on rock type. The degree of dependence of the three relationships on rock type is explained on the basis of differences in rock properties affecting the measured parameters.