The Effects of Confining Pressure and Fluid Saturation on Ultrasonic Velocities in Rocks

Laboratory measurements of ultrasonic p- and S-wave velocities were made as a function of confining pressure for vacuum dry, benzene-, and water-saturated samples of Westerly granite, Bedford limestone, and Weber, Navajo, Berea, and Kayenta sandstones. The measurements indicate: 1) water-saturated bulk moduli are higher than benzene-saturated values, 2) fluid-saturated shear moduli are always greater than or equal to dry values, and 3) water-saturated shear moduli for the sandstones are higher than benzene values at low pressure while lower than both benzene and dry values at higher pressure, Indicating that an apparent water-softening effect Is concentrated In the shear modulus. Modelling of the velocity measurements with the Blot (1956a) and Gassmann (1951) equations for static effective bulk modulus indicates that it underestimates the increase in bulk modulus and velocities caused by fluid saturation. Inertial effects of the pore fluid as treated by Blot (1956a, 1956b) are also shown to give minimal improvement to predicted velocities, which are underestimated. Velocity measurements are modelled with the Cheng-Kuster-Toksoz ellipsoidal pore and crack model using the inversion technique developed by Cheng (1978). Fits of dry and benzene-saturated velocities are shown along with pore aspect ratio distributions at zero pressure. Water-saturated velocity data and measured porosity reductions with pressure are compared with predictions of the model

Experimental Determination of Elastic Anisotropy of Berea Sandstone, Chicopee Shale and Chelmsford Granite

We use the ultrasonic transmission method to measure P-, SH-, and SV-wave velocities for Chelmsford Granite, Chicopee Shale, and Berea Sandstone in different directions up to 1000 bars confining pressure. The velocity measurements indicate that these three rocks are elastically anisotropic. The stiffness constants, dynamic Young's moduli, dynamic Poisson's ratios, and dynamic bulk moduli of these three rocks were also calculated. These elastic constants, together with velocity measurements, suggest that: (1) Elastic anisotropy is due to the combined effects of pores/cracks and mineral grain orientation. (2) Elastic anisotropy decreases with increasing confining pressure. The residual anisotropy at higher confining pressure is due to mineral grain orientation

Photography-based taxonomy is inadequate, unnecessary, and potentially harmful for biological sciences

The question whether taxonomic descriptions naming new animal species without type specimen(s) deposited in collections should be accepted for publication by scientific journals and allowed by the Code has already been discussed in Zootaxa (Dubois & Nemésio 2007; Donegan 2008, 2009; Nemésio 2009a–b; Dubois 2009; Gentile & Snell 2009; Minelli 2009; Cianferoni & Bartolozzi 2016; Amorim et al. 2016). This question was again raised in a letter supported by 35 signatories published in the journal Nature (Pape et al. 2016) on 15 September 2016. On 25 September 2016, the following rebuttal (strictly limited to 300 words as per the editorial rules of Nature) was submitted to Nature, which on 18 October 2016 refused to publish it. As we think this problem is a very important one for zoological taxonomy, this text is published here exactly as submitted to Nature, followed by the list of the 493 taxonomists and collection-based researchers who signed it in the short time span from 20 September to 6 October 2016

Effects of stress, pore pressure, and pore fluids on bulk strain, velocity, and permeability in rocks

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric and Planetary Sciences, 1984.MICROFICHE COPY AVAILABLE IN ARCHIVES AND LINDGREN.Bibliography: leaves 317-322.by Karl B. Coyner.Ph.D

Laboratory Measurements of Attenuation in Rocks at Ultrasonic Frequencies

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