Kenneth W. Winkler
Schlumberger Res., Old Quarry Rd., Ridgefield, CT 06877
Western Atlas Logging Services, Houston, TX 77042
Third-order elasticity successfully describes a variety of acoustic phenomenon in many materials, and measurements exist of third-order elastic constants in metals, plastics, and crystals. A key feature of third-order elasticity theory is that acoustic velocities vary with the stress in a material. In spite of the fact that velocities in rocks are extremely stress dependent, no measurements have previously been published of third-order elastic constants in sedimentary rocks. This experimental technique is based on measuring changes in velocity with applied stress, both uniaxial stress and hydrostatic stress. By measuring five acoustic modes there is an overdetermined system of five equations and three unknowns. Measurements are reported of the three third-order elastic constants for nine rocks (sandstones, limestones, granite) and a few synthetic materials at ambient room conditions. Along with velocity, porosity, density, and uniaxial strength, these data constitute a unique database of rock properties.