Simultaneous determination of compressional and shear elastic wave velocities in Canadian east coast sedimentary rocks as functions of pressure and temperature

Gagnon, Robert E. (1981) Simultaneous determination of compressional and shear elastic wave velocities in Canadian east coast sedimentary rocks as functions of pressure and temperature. Masters thesis, Memorial University of Newfoundland.

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Abstract

An apparatus has been designed and constructed to determine accurately, using the pulse transmission method, compressional (± 1%) and shear (± 2%) wave velocities as functions of temperature and pressure. A significant feature of the design, made possible by stacking the piezoelectric transmitting and receiving P and S-wave transducers, is the ability to measure both shear and compressional velocities with each experiment. The device has been employed to study sedimentary core samples taken from wells on the Labrador Shelf and the Grand Banks of Newfoundland. With a few exceptions the results show qualitative agreement with Biot’s theory for propagation of elastic waves through porous solids. Comparison with well log velocities, however, shows significant discrepancies which arise for several reasons. – Velocity anisotropy has been observed between samples taken parallel and perpendicular to the bedding plane. The most extreme case exhibited an anisotropic effect of 10%. The dominant mechanisms proposed to explain anisotropy are crack and pore alignment and inhomogeneous distribution of rock constituents. – The effect of temperature is found to be small compared with the influence of hydrostatic pressure. A 40°C change in temperature in the range studied (7°C - 90°C) does not affect velocities by more than 2%.

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