| Summary: | The spectral ratio method is used to calculate the quality factor (Q) in porous
rock samples at ultrasonic frequencies (0.3 - 1.5 MHz). The data were collected
using the pulse transmission technique with aluminum used as a high Q standard. The
data set consists of dry, water and benzene saturated rocks at differential
pressures from zero to one kilobar. Two sandstones, Berea and Kayenta, Bedford
limestone, and Webatuck dolomite are studied. Water and benzene were chosen as
pore fluid saturants to contrast the effects of two different pore fluids (density,
compressibility, viscosity, dielectric constant, and wetting properties) at ultrasonic
frequencies. The main features observed are: 1) The quality factor Q increases with
increasing confining pressure; at low pressures the rate of increase is larger. 2) Q
for saturated samples is generally lower than for dry samples. 3) The introduction of
a fluid saturant into a dry rock increases S-wave attenuation more than P-wave
attenuation. 4) In general, given the measurement error and the fact that these
results are preliminary, the differences in attenuation between the two fluid
saturations, water and benzene, are not large. Nevertheless, we observe that
benzene-saturated attenuations are slightly higher than water-saturated values,
particularly at lower pressures (less than 500 bars) for the P-wave.
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