On: “Effects of porosity and clay content on wave velocities in sandstones” by D. Han, A. Nur, and D. Morgan (GEOPHYSICS, 51, 2093–2107, November 1986”.

Geophysics ◽  
1987 ◽  
Vol 52 (10) ◽  
pp. 1439-1439 ◽  
Author(s):  
David C. Nobes ◽  
George Schneider ◽  
Stephen Hodgson
Keyword(s):  
Physical Model ◽  
Seismic Velocity ◽  
Statistical Significance ◽  
Physical Property ◽  
Clay Content ◽  
Related Question ◽  
Wave Velocities ◽  
Physical Principles

At the outset, we must declare our philosophical bias: we believe that, if at all possible, equations relating one physical property to another should be based on some physical model. If there are two equations that can be said to relate one property to another equally well, within statistical bounds, then the equation that is based on physical principles is preferable. We acknowledge that the relationships among in this case, porosity, clay content, and seismic velocity are not always clear or easily tested, and we appreciate the efforts of Han et al. However, we have a comment and a related question regarding the statistical significance of their results.

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.

Failure of Rubber by Abrasion

1985 ◽  
Vol 58 (3) ◽  
pp. 653-661 ◽  
Author(s):  
Carl T. R. Pulford
Keyword(s):  
Abrasive Wear ◽  
Physical Model ◽  
Abrasion Resistance ◽  
Short Review ◽  
Wear Model ◽  
Fracture Properties ◽  
Tire Wear ◽  
Physical Principles

Abstract This short review presents the landmark discoveries and ideas in rubber abrasion that have brought the field to where it is today. First, the important features of rubber abrasion are reviewed as background for a physical model for the abrasion of rubber. The model, due to Thomas, is described in detail, since it clearly shows the connection between the failure of rubber by abrasive wear and the appropriate rubber fracture properties. The implications of the model for improved abrasion resistance are also discussed. Then, physical principles are applied to the failure of rubber by abrasion in actual products, such as tires. The tire wear model of Schallamach and Turner is described, together with its success in explaining several features of tire wear.

Case study: Seismic resolution and reservoir characterization of thin sands using multiattribute analysis and bandwidth extension in the Daqing field, China

2020 ◽  
Vol 8 (1) ◽  
pp. T89-T102
Author(s):  
David Mora ◽  
John Castagna ◽  
Ramses Meza ◽  
Shumin Chen ◽  
Renqi Jiang
Keyword(s):  
Seismic Data ◽  
Reservoir Characterization ◽  
Statistical Significance ◽  
Physical Property ◽  
Seismic Attributes ◽  
Oil Field ◽  
Thin Layers ◽  
Inversion Method ◽  
Bandwidth Extension ◽  
Multiattribute Analysis

The Daqing field, located in the Songliao Basin in northeastern China, is the largest oil field in China. Most production in the Daqing field comes from seismically thin sand bodies with thicknesses between 1 and 15 m. Thus, it is not usually possible to resolve Daqing reservoirs using only conventional seismic data. We have evaluated the effectiveness of seismic multiattribute analysis of bandwidth extended data in resolving and making inferences about these thin layers. Multiattribute analysis uses statistical methods or neural networks to find relationships between well data and seismic attributes to predict some physical property of the earth. This multiattribute analysis was applied separately to conventional seismic data and seismic data that were spectrally broadened using sparse-layer inversion because this inversion method usually increases the vertical resolution of the seismic. Porosity volumes were generated using target porosity logs and conventional seismic attributes, and isofrequency volumes were obtained by spectral decomposition. The resulting resolution, statistical significance, and accuracy in the determination of layer properties were higher for the predictions made using the spectrally broadened volume.

Reply by the authors to Nobes, Schneider, and Hodgson

Geophysics ◽  
1987 ◽  
Vol 52 (10) ◽  
pp. 1439-1441
Author(s):  
D. Han ◽  
A. Nur ◽  
D. Morgan
Keyword(s):  
Physical Model ◽  
Physical Property ◽  
Average Model

We agree with Nobes et al. that our own bias, like theirs, is that “If at all possible equations relating one physical property to another should be based on some physical model,” but in addition we believe also that such a model must be correct, or at least physically sound. It is on the issue of the soundness of the traveltime average model that we fundamentally disagree with Nobes et al.

Effects of Porosity and Clay Content on P- and S-wave Velocities in Cooper Basin Sandstones

2000 ◽  
Vol 31 (1-2) ◽  
pp. 433-440 ◽  
Author(s):  
Abbas Khaksar ◽  
Cedric Griffiths
Keyword(s):  
Clay Content ◽  
S Wave ◽  
Wave Velocities ◽  
Cooper Basin

A physical model study of shear‐wave splitting and fracture intensity

Geophysics ◽  
1992 ◽  
Vol 57 (4) ◽  
pp. 647-652 ◽  
Author(s):  
Robert H. Tatham ◽  
Martin D. Matthews ◽  
K. K. Sekharan ◽  
Christopher J. Wade ◽  
Louis M. Liro
Keyword(s):  
Physical Model ◽  
Shear Wave ◽  
Shear Wave Splitting ◽  
Constant Thickness ◽  
Petroleum Reservoir ◽  
Wave Velocities ◽  
Shear Wave Velocities ◽  
Wave Splitting ◽  
Fracture Intensity ◽  
Degree Of Anisotropy

In a series of physical model experiments, fractured media are simulated by stacks of thin Plexiglas sheets clamped together tightly to form blocks. The plates are assembled underwater, and a very thin water layer between the sheets prevents formation of an effectively welded interface between them. Thus, the stacked material is not a series of welded plates but rather a truly fractured medium simulating a potential petroleum reservoir with only fracture porosity and permeability. Sheets of constant thickness are used, but the intensity of fracturing between the different models is simulated by using different thicknesses of Plexiglas for each model. Observation of direct shear‐wave arrivals through the stack, with propagation parallel to the sheets and polarization of particle motion allowed to be parallel to, normal to, or in any arbitrary angle to the sheets, definitively demonstrate the existence of shear‐wave splitting and hence anisotropy. For Plexiglas sheets 1/16 in thick (0.16 cm) representing a fracture intensity of about 16 fractures per wavelength, shear‐wave splitting and hence anisotropy are clearly observed. For greater fracture intensities (i.e., thinner plates) the degree of anisotropy is greater, and for less intense fracturing (i.e., thicker plates), the degree of anisotropy is less. These experimental data suggest that for fracture intensities of greater than about 10 fractures per wavelength there is a simple relation between fracture intensity and degree of anisotropy in two different polarizations of shear waves. For fracture intensities less than a threshold of about 10 per wavelength, there is no simple observed relation between them. Further, the faster of the split shear‐wave velocities is near the solid material velocity, and the observed variation in velocity for various fracture intensities is in the slower of the split shear‐wave velocities.

scholarly journals A laboratory exercise using a physical model for demonstrating countercurrent heat exchange

2012 ◽  
Vol 36 (1) ◽  
pp. 58-62
Author(s):  
Catherine Loudon ◽  
Elizabeth C. Davis-Berg ◽  
Jason T. Botz
Keyword(s):  
Blood Flow ◽  
Heat Exchange ◽  
Blood Vessels ◽  
Physical Model ◽  
Circulatory System ◽  
Concentration Gradients ◽  
Laboratory Exercise ◽  
Permeable Barrier ◽  
Countercurrent Exchange ◽  
Physical Principles

A physical model was used in a laboratory exercise to teach students about countercurrent exchange mechanisms. Countercurrent exchange is the transport of heat or chemicals between fluids moving in opposite directions separated by a permeable barrier (such as blood within adjacent blood vessels flowing in opposite directions). Greater exchange of heat or chemicals between the fluids occurs when the flows are in opposite directions (countercurrent) than in the same direction (concurrent). When a vessel loops back on itself, countercurrent exchange can occur between the two arms of the loop, minimizing loss or uptake at the bend of the loop. Comprehension of the physical principles underlying countercurrent exchange helps students to understand how kidneys work and how modifications of a circulatory system can influence the movement of heat or chemicals to promote or minimize exchange and reinforces the concept that heat and chemicals move down their temperature or concentration gradients, respectively. One example of a well-documented countercurrent exchanger is the close arrangement of veins and arteries inside bird legs; therefore, the setup was arranged to mimic blood vessels inside a bird leg, using water flowing inside tubing as a physical proxy for blood flow within blood vessels.

scholarly journals The influence of clay-sized particles on seismic velocity for Canadian Arctic permafrost

1984 ◽  
Vol 21 (1) ◽  
pp. 19-24 ◽  
Author(s):  
M. S. King
Keyword(s):  
Wave Velocity ◽  
Seismic Velocity ◽  
Pore Space ◽  
Canadian Arctic ◽  
Clay Content ◽  
Compressional Wave ◽  
Specimen Preparation ◽  
Compressional Wave Velocity ◽  
Confining Stress ◽  
Ice Content

Seismic-wave velocities have been measured on 37 unconsolidated permafrost samples as a function of temperature in the range -16 to +5 °C. The samples, taken from a number of locations in the Canadian Arctic islands, the Beaufort Sea, and the Mackenzie River valley, were tighty sealed immediately upon recovery in several layers of polyethylene film and maintained in their frozen state during storage, specimen preparation, and until they were tested under controlled environmental conditions. During testing, the specimens were subjected to a constant hydrostatic confining stress of 0.35 MPa (50 psi) under drained conditions. At no stage was a deviatoric stress applied to the permafrost specimens. The fraction of clay-sized particles in the test specimens varied from almost zero to approximately 65%. At temperatures below -2 °C the compressional-wave velocity was observed to be a strong function of the fraction of clay-sized particles, but only a weak function of porosity. At temperatures above 0 °C the compressional-wave velocity was observed to be a function only of porosity, with virtually no dependence upon the fraction of clay-sized particles. Calculation of the fractional ice content of the permafrost pore space from the Kuster and Toksöz theory showed that for a given fraction of clay-sized particles the ice content increases with an increase in porosity. It is concluded that the compressional-wave velocity for unconsolidated permafrost from the Canadian Arctic is a function of the water-filled porosity, irrespective of the original porosity, clay content, or temperature.

scholarly journals A Seismic Reconnaissance in the Mcmurdo Sound Region, Antarctica

1966 ◽  
Vol 6 (44) ◽  
pp. 209-221 ◽  
Author(s):  
Robin A. I. Bell
Keyword(s):  
Seismic Velocity ◽  
Seismic Refraction ◽  
P Wave ◽  
Velocity Measurements ◽  
Frozen Ground ◽  
Mcmurdo Sound ◽  
Wave Velocities ◽  
Taylor Valley ◽  
Minimum Age ◽  
First Arrival

AbstractA portable first-arrival seismic refraction instrument was used to measure seismic P-wave velocities in ice, frozen ground, till and shattered rock at various places in the McMurdo Sound region, Antarctica. It was found that some frozen ground exhibits the same seismic velocity as ice, so that buried ice cannot be idengified by seismic velocity measurements.The depth of exfoliation of a granite outcrop in Taylor Valley was successfully measured, as was the depth of an ice-free moraine in Wright Valley. From this latter depth, and from reasonable assumptions about the diffusion of water vapour through till, a minimum age of 75,000 yr. has been deduced for the moraine. This age implies that no through-glacier occupied Wright Valley during the last Northern Hemisphere glaciation.

SEISMIC VELOCITY STUDY OF SYNTHETIC CORES

Geophysics ◽  
1957 ◽  
Vol 22 (4) ◽  
pp. 813-820 ◽  
Author(s):  
William O. Murphy ◽  
Joseph W. Berg ◽  
Kenneth L. Cook
Keyword(s):  
Elastic Wave ◽  
Elastic Waves ◽  
Atmospheric Pressure ◽  
Room Temperature ◽  
Seismic Velocity ◽  
Pore Filling ◽  
The Core ◽  
Wave Velocities ◽  
Longitudinal Elastic Wave ◽  
Alcohol Benzene

The velocity of a longitudinal elastic wave through rock at room temperature and at atmospheric pressure depends upon the nature of the rock frame, the porosity of the rock, and the nature of the pore‐filling fluid. In the present investigation longitudinal elastic wave velocities were measured for sixty synthetic cores. The rock frame consisted of sorted quartz sand grains and cement, the percentage of cement varying from ten to fifty percent. The core porosities varied from 8.8 percent to 22 percent. The velocities were measured for dry air‐filled cores and for cores saturated with various liquids. These pore‐filling liquids were distilled water, ethyl alcohol, benzene, carbon tetrachloride, and chloroform. The measured velocities ranged from 2,360 feet per second to 14,710 feet per second. The wave velocity in liquid‐filled cores of 10 percent porosity was approximately twice the velocity for cores of 20 percent porosity, the same type of cement being used in both instances. For any given core, flooded with fluids of wave velocities ranging from 3,000 to 5,000 feet per second, the maximum observed variation in core velocity was around 20 percent. The experimental data fitted the empirical linear equation [Formula: see text] where [Formula: see text] of longitudinal elastic waves passing through the flooded core; [Formula: see text] of longitudinal elastic waves in passing through the saturating fluid. The constant k depends upon the porosity of the rock and the type of cement used. The constant, C, depends upon the nature of the rock frame.

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