Acoustic velocities and electrical properties of frozen sandstones and shales

1977 ◽  
Vol 14 (5) ◽  
pp. 1004-1013 ◽  
Author(s):  
M. S. King
Keyword(s):  
Electrical Resistivity ◽  
Electrical Properties ◽  
Phase Angle ◽  
The Arctic ◽  
Frequency Range ◽  
Ultrasonic Velocities ◽  
Sharp Reduction ◽  
Wave Velocities ◽  
Shear Wave Velocities ◽  
Acoustic Velocities

Ultrasonic velocities and electrical properties have been measured in the laboratory at permafrost temperatures on a number of samples of sandstones and a shale which had been recovered from boreholes in the arctic and stored in their natural frozen state. Compressional and shear-wave velocities, electrical resistivity, and phase-angle relationships in the frequency range 0.005–100 kHz have been measured on the permafrost samples, at temperatures in the range −18 °C–+4 °C.Results of the tests show that, at a particular temperature, there is a small decrease in the electrical resistivity measured on all samples tested as the frequency is increased. The phase-angle differences measured show no consistent relationship with either frequency or temperature, but they are all less than 12° in magnitude. The electrical resistivity at a particular frequency and the ultrasonic velocities are affected in a similar manner by changes in temperature. Whereas the sandstones show a sharp reduction in velocities and resistivity as the temperature is raised to 0 °C or above, the shale shows little dependence of these parameters on changes in temperature in the range tested. An increase in shale content of the sandstone results in behavior intermediate between that of a clean sandstone and that of a shale.

scholarly journals Ultrasonic Pulse Velocities And Dynamic Elastic Constants Of Sandstones From The Semanggol Formation, Beris Dam, Kedah Darul Aman

Warta Geologi ◽  
2021 ◽  
Vol 47 (1) ◽  
pp. 1-8
Author(s):  
John K. Raj
Keyword(s):  
Grain Size ◽  
Elastic Constants ◽  
Ultrasonic Pulse ◽  
Coarse Grained ◽  
Unconfined Compression ◽  
Ultrasonic Velocities ◽  
Unconfined Compression Test ◽  
Fine Grained ◽  
Wave Velocities ◽  
Shear Wave Velocities

The main Beris Dam is founded on a sequence of thick bedded conglomerates and pebbly to fine grained sandstones with minor mudstone mapped as the Semanggol Formation of Triassic age. Ultrasonic pulse measurements show velocities of compressional and shear waves through the sandstones to increase with decreasing grain size; the pebbly sandstone with velocities of 2.210, and 5.171, km/s, and the coarse grained sandstone with velocities of 2.477, and 5.612, km/s, respectively. The medium grained sandstones have compressional and shear wave velocities of 2.457, and 5.793, km/s and the fine grained sandstones, velocities of 2.572, and 5.867 km/s, respectively. Dynamic elastic constants computed from the ultrasonic velocities also increase in values with decreasing grain size; Poisson’s ratio varying from 0.36 to 0.39, the modulus of elasticity from 35.076 to 48.210 GPa, the bulk modulus from 52.260 to 67.362 GPa and the modulus of rigidity from 12.637 to 17.468 GPa. Increasing velocities and elastic constants with decreasing grain size are considered to result from a denser arrangement of constituent grains as shown by increasing dry unit weights. Comparison with the results of an unconfined compression test on a fine grained sandstone indicate that the ultrasonic elastic constants are good approximations of static elastic constants.

VSP measurement of shear‐wave velocities in consolidated and poorly consolidated formations

Geophysics ◽  
1992 ◽  
Vol 57 (12) ◽  
pp. 1583-1592 ◽  
Author(s):  
John O’Brien
Keyword(s):  
Shear Wave ◽  
Poisson’S Ratio ◽  
Mode Conversion ◽  
Shear Waves ◽  
Vertical Motion ◽  
Seismic Source ◽  
Poisson's Ratio ◽  
The Arctic ◽  
Wave Velocities ◽  
Shear Wave Velocities

Mode conversion in the subsurface can generate shear waves with sufficient amplitude so that they can be used to measure shear‐wave propagation effects. Significant mode conversion can occur even at near vertical incidence if there is sufficient contrast in Poisson’s ratio across the interface. This can be exploited to measure shear‐wave velocities in the underlying section in the course of vertical seismic profile (VSP) acquisition. The technique is effective even in poorly consolidated formations with low shear‐wave velocities where sonic waveform logging fails. Where shear‐wave velocity data are available from sonic waveform logs, the VSP data can be used to verify the wireline data and to calibrate these data to seismic frequencies. The technique is illustrated with a case study from the North Slope, Alaska, in which several shear‐wave events are observed propagating downward through the subsurface. The seismic source is a vertical‐motion vibrator; shear waves are generated via mode conversion in the subsurface and also radiated from the source at the surface, and they are observed with both far‐ and near‐source offsets. The shear‐wave events are strong even on the near‐offset data, which is attributed to the contrast in Poisson’s ratio at the interfaces where mode conversion occurs. The technique is not limited to the hard surfaces of the Arctic and should work in any well, either land or marine, that penetrates shallow interfaces where mode conversion can occur.

Elastic properties of gas hydrate‐bearing sediments

Geophysics ◽  
2001 ◽  
Vol 66 (3) ◽  
pp. 763-771 ◽  
Author(s):  
Myung W. Lee ◽  
Timothy S. Collett
Keyword(s):  
Shear Wave ◽  
Elastic Properties ◽  
Gas Hydrate ◽  
Poisson’S Ratio ◽  
Pore Space ◽  
Poisson's Ratio ◽  
The Arctic ◽  
Wave Velocities ◽  
Shear Wave Velocities ◽  
Hydrate Bearing Sediments

Downhole‐measured compressional- and shear‐wave velocities acquired in the Mallik 2L-38 gas hydrate research well, northwestern Canada, reveal that the dominant effect of gas hydrate on the elastic properties of gas hydrate‐bearing sediments is as a pore‐filling constituent. As opposed to high elastic velocities predicted from a cementation theory, whereby a small amount of gas hydrate in the pore space significantly increases the elastic velocities, the velocity increase from gas hydrate saturation in the sediment pore space is small. Both the effective medium theory and a weighted equation predict a slight increase of velocities from gas hydrate concentration, similar to the field‐observed velocities; however, the weighted equation more accurately describes the compressional- and shear‐wave velocities of gas hydrate‐bearing sediments. A decrease of Poisson’s ratio with an increase in the gas hydrate concentration is similar to a decrease of Poisson’s ratio with a decrease in the sediment porosity. Poisson’s ratios greater than 0.33 for gas hydrate‐bearing sediments imply the unconsolidated nature of gas hydrate‐bearing sediments at this well site. The seismic characteristics of gas hydrate‐bearing sediments at this site can be used to compare and evaluate other gas hydrate‐bearing sediments in the Arctic.

The influence of salinity on acoustic and electrical properties of frozen soils

2019 ◽  
pp. 99-106
Author(s):  
A. V. Koshurnikov ◽  
P. I. Kotov ◽  
I. A. Agapkin
Keyword(s):  
Electrical Resistivity ◽  
Electrical Properties ◽  
Water Content ◽  
Soil Salinity ◽  
Pore Solution ◽  
Saline Soils ◽  
Frozen Soils ◽  
Longitudinal Waves ◽  
Wave Velocities ◽  
Specific Electrical Resistivity

The results of determining acoustic and electrical properties of frozen saline soils (sand and silt) of massive cryogenic texture at different water content (3 values for each type of soil), salinity (7 values for silt and 5 for sand) and temperatures (–2, –4, –6 ᵒC) are given in the article. As a result, data on the high correlation between specific electrical resistivity and concentration of the pore solution and between ratio of a concentration of the pore solution to temperature and the velocity of longitudinal waves were obtained. Electrical resistivity can decrease by 2–22 times during the transition from a low-saline to a highly saline state and for longitudinal wave velocities only two times. Therefore, it is the electrical properties that are most suitable for the ranking of soils by the degree of salinity.

scholarly journals Longitudinal and Shear Wave Velocities Measurement in Compacted Bentonite for Water Content

2018 ◽  
Vol 43 ◽  
pp. 01016
Author(s):  
Shun Kimura ◽  
Kazumi Kitayama ◽  
Hideharu Takahashi ◽  
Kazushi Kimoto ◽  
Katsuyuki Kawamura ◽  
...  
Keyword(s):  
Bulk Modulus ◽  
Water Content ◽  
Degree Of Saturation ◽  
Ultrasonic Velocities ◽  
Compacted Bentonite ◽  
Wave Velocities ◽  
Shear Wave Velocities ◽  
Bentonite Buffer ◽  
Buffer Material

Bentonite is a good candidate of buffer material for disposal repository of high-level radioactive waste. Understanding groundwater behavior in bentonite buffer material is important in order to evaluate the bentonite buffer performance and guarantee long-term safety. Elastic constants of the bentonite buffer material are important parameters for the long-term safety. Water content in buffer material may have an influence on its elastic properties. For this reason, the monitoring system of the water saturation level in compacted bentonite is required. In this study, the ultrasonic velocity measurement method for evaluation of water content in compacted bentonite was proposed. At first, the effect of a degree of saturation in compacted bentonite on the longitudinal and shear wave velocities was investigated experimentally. In addition, the elastic property, bulk modulus, in unsaturated compacted bentonite were evaluated by ultrasonic velocities. As a result, it can be confirmed that ultrasonic velocities can evaluate a degree of saturation and bulk modulus of compacted bentonite.

Soil moisture assessment by means of compressional and shear wave velocities: Theoretical analysis and experimental setup

Measurement ◽  
2010 ◽  
Vol 43 (3) ◽  
pp. 344-352 ◽  
Author(s):  
F. Adamo ◽  
F. Attivissimo ◽  
L. Fabbiano ◽  
N. Giaquinto ◽  
M. Spadavecchia
Keyword(s):  
Soil Moisture ◽  
Theoretical Analysis ◽  
Shear Wave ◽  
Experimental Setup ◽  
Wave Velocities ◽  
Shear Wave Velocities

The relation between seismic P‐ and S‐wave velocity dispersion in saturated rocks

Geophysics ◽  
1994 ◽  
Vol 59 (1) ◽  
pp. 87-92 ◽  
Author(s):  
Gary Mavko ◽  
Diane Jizba
Keyword(s):  
Wave Velocity ◽  
Large Scale ◽  
Velocity Dispersion ◽  
Seismic Velocity ◽  
Ultrasonic Velocities ◽  
S Wave ◽  
Local Flow ◽  
Wave Velocities ◽  
Shear Compliance

Seismic velocity dispersionin fluid-saturated rocks appears to be dominated by tow mecahnisms: the large scale mechanism modeled by Biot, and the local flow or squirt mecahnism. The tow mechanisms can be distuinguished by the ratio of P-to S-wave dispersions, or more conbeniently, by the ratio of dynamic bulk to shear compliance dispersions derived from the wave velocities. Our formulation suggests that when local flow denominates, the dispersion of the shear compliance will be approximately 4/15 the dispersion of the compressibility. When the Biot mechanism dominates, the constant of proportionality is much smaller. Our examination of ultrasonic velocities from 40 sandstones and granites shows that most, but not all, of the samples were dominated by local flow dispersion, particularly at effective pressures below 40 MPa.

Sign in / Sign up

Export Citation Format

Share Document