| Summary: | A set of ultrasonic experiments was carried out to determine the effects of horizontal and vertical fractures on full waveform acoustic logs. Boreholes of 1 cm diameter were drilled in aluminum blocks. Measurements were made with horizontal fractures of 0.05 mm, 1.0 mm, 2.5 mm, and 4.5 mm width and a vertical fracture of 1.0 mm width. The horizontal
fractures of even the smallest thickness significantly attenuate the P, S, and pseudo-Rayleigh waves. The Stoneley waves are the least attenuated, and attenuation increases
with increasing fracture width. The vertical fracture attenuates Stoneley waves most
significantly. Both scattering and fluid flow playa role in attenuation. The results may
qualitatively be extended to inclined open fractures, where we expect strong attenuation
of P and S waves and moderate attenuation of Stoneley waves.
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