Physical and elastic properties of some khondalites from the Eastern Ghat Belt of Peninsular India

1976 ◽  
Vol 13 (9) ◽  
pp. 1333-1342 ◽  
Author(s):  
B. S. Gogte ◽  
Y. V. Ramana
Keyword(s):  
Elastic Wave ◽  
Manganese Oxide ◽  
Elastic Properties ◽  
Fracture Strength ◽  
Elastic Wave Velocity ◽  
Eastern Ghats ◽  
Peninsular India ◽  
Wave Velocities ◽  
Shear Wave Velocities ◽  
Rock Suite

Khondalites, which form an important rock suite of the Eastern Ghats, are studied for their physical and elastic properties together with their petrology and petrochemistry. Garnetiferous quartzites exhibit compressional and shear wave velocities between 4.9–5.6 km/s and 2–3 km/s; these are higher than garnet sillimanite gneisses, which are between 3.4–5.2 km/s and 1.4–2.6 km/s, respectively. The latter are more anisotropic than the former. Velocity and anisotropy are affected by alteration of garnet and sillimanite in these rocks. The velocities show a decreasing tendency with increasing manganese oxide. Garnetiferous quartzites bear a higher fracture strength than garnet sillimanite gneisses. Elastic wave velocity studies under hydrostatic pres sure to 5 kbar indicate slight changes with increasing pressure; and the absence of kyanite and the presence of cordierite in negligible amounts suggest their formation near the low to intermediate pressure granulite field.

scholarly journals Modified Fixed Wall Oedometer When Considering Stress Dependence of Elastic Wave Velocities

Sensors ◽  
2020 ◽  
Vol 20 (21) ◽  
pp. 6291
Author(s):  
Jong-Sub Lee ◽  
Geunwoo Park ◽  
Yong-Hoon Byun ◽  
Changho Lee
Keyword(s):  
Elastic Wave ◽  
Shear Wave ◽  
Compressional Wave ◽  
Stress Dependence ◽  
Bender Elements ◽  
Wave Velocities ◽  
Shear Wave Velocities ◽  
Vertical Effective Stress ◽  
Side Friction ◽  
Applied Stresses

A modified oedometer cell for measuring the applied stresses and elastic waves at the top and bottom of the specimen is developed to evaluate the effect of the side friction on the stress dependence of the elastic wave velocities. In the modified cell, two load cells are installed at the top and bottom plates, respectively. To generate and detect the compressional and shear waves, a pair of piezo disk elements and a pair of bender elements are mounted at both the top and bottom plates. Experimental results show that the stresses measured at the bottom are smaller than those measured at the top during the loading and vice versa during unloading, regardless of the densities and heights of the specimens. Under nearly saturated conditions, the compressional wave velocities remain almost constant for the entire stress state. With plotting stresses measured at top, the shear wave velocities during unloading are greater than those during loading, whereas with plotting stresses measured at bottom, the shear wave velocities during unloading are smaller than those during loading owing to the side friction. The vertical effective stress may be simply determined from the average values of the stresses measured at the top and bottom of the specimens.

Seismic study of crustal structure in Pennsylvania and New York*

1955 ◽  
Vol 45 (4) ◽  
pp. 303-325 ◽  
Author(s):  
Samuel Katz
Keyword(s):  
New York ◽  
Elastic Wave ◽  
Upper Mantle ◽  
Compressional Wave ◽  
Compressional Wave Velocity ◽  
Wave Velocities ◽  
Shear Wave Velocities ◽  
Central Pennsylvania ◽  
Significant Difference ◽  
Mohorovičić Discontinuity

Abstract Blasts at two quarries in northern New York and central Pennsylvania have been recorded to a distance of 309 km. The data indicate an essentially homogeneous, unlayered crust, with elastic wave velocities possibly increasing with depth. An average crustal thickness for the region is 34.4 km., with no indication of significant difference in thickness between the two areas. Observed compressional wave velocities for the crust are 6.39 and 6.31 km/sec. for New York, and 6.04 km/sec. for Pennsylvania. The corresponding shear wave velocities are 3.62 and 3.60 km/sec., and 3.61 km/sec. Average upper mantle velocities are 8.14 km/sec. for Pn and 4.69 km/sec. for Sn. The compressional wave velocity of anorthosite near Tahawus, N.Y., is 6.63 km/sec. No near-vertical reflections from the Mohorovičić discontinuity were observed.

Estimation of Dry-Rock Elastic Moduli Based on the Simulation of Mud-Filtrate Invasion Effects on Borehole Acoustic Logs

2009 ◽  
Vol 12 (06) ◽  
pp. 898-911 ◽  
Author(s):  
Tobiloluwa B. Odumosu ◽  
Carlos Torres-Verdín ◽  
Jesús M. Salazar ◽  
Jun Ma ◽  
Benjamin Voss ◽  
...  
Keyword(s):  
Bulk Modulus ◽  
Shear Wave ◽  
Elastic Properties ◽  
Elastic Moduli ◽  
Compressional Wave ◽  
Shear Rigidity ◽  
Spatial Distributions ◽  
Wave Velocities ◽  
Shear Wave Velocities ◽  
Mud Filtrate

Summary Reliable estimates of dry-rock elastic properties are critical to the accurate interpretation of the seismic response of hydrocarbon reservoirs. We describe a new method for estimating elastic moduli of rocks in-situ based on the simulation of mud-filtrate invasion effects on resistivity and acoustic logs. Simulations of mud-filtrate invasion account for the dynamic process of fluid displacement and mixing between mud-filtrate and hydrocarbons. The calculated spatial distributions of electrical resistivity are matched against resistivity logs by adjusting the underlying petrophysical properties. We then perform Biot-Gassmann fluid substitution on the 2D spatial distributions of fluid saturation with initial estimates of dry-bulk (kdry) modulus and shear rigidity (µdry) and a constraint of Poisson's ratio (?d) typical of the formation. This process generates 2D spatial distributions of compressional and shear-wave velocities and density. Subsequently, sonic waveforms are simulated to calculate shear-wave slowness. Initial estimates of the dry-bulk modulus are progressively adjusted using a modified Gregory-Pickett (1963) solution of Biot's (1956) equation to estimate a shear rigidity that converges to the well-log value of shear-wave slowness. The constraint on dynamic Poisson's ratio is then removed and a refined estimate of the dry-bulk modulus is obtained by both simulating the acoustic log (monopole) and matching the log-derived compressional-wave slowness. This technique leads to reliable estimates of dry-bulk moduli and shear rigidity that compare well to laboratory core measurements. Resulting dry-rock elastic properties can be used to calculate seismic compressional-wave and shear-wave velocities devoid of mud-filtrate invasion effects for further seismic-driven reservoir-characterization studies.

TOTAL POROSITY AND MATRIX PARAMETERS OF CARBONATE ROCKS BASED ON THE ELASTIC WAVE VELOCITY AND DENSITY MEASUREMENTS

2018 ◽  
Vol 473 (473) ◽  
pp. 13-26
Author(s):  
Jadwiga JARZYNA ◽  
Edyta PUSKARCZYK ◽  
Ewa OGÓREK ◽  
Jacek MOTYKA
Keyword(s):  
Elastic Wave ◽  
Elastic Waves ◽  
Total Porosity ◽  
Elastic Wave Velocity ◽  
P Wave ◽  
Reservoir Properties ◽  
Rock Samples ◽  
Additional Information ◽  
Wave Velocities ◽  
Boundary Velocity

The purpose of the research was to find relationship between elastic waves velocities obtained from lab measurements and parameters from hydrogeological research. Measurements were conducted on 73 rock samples originating mostly from Jurassic limestone of the Olkusz area. Additional information about the rock samples was obtained when the elastic wave velocities were compared with reservoir parameters such as porosity, permeability and density. Plots of elastic waves velocities vs. porosity and bulk density vs. porosity gave information about the range of P wave velocities from the boundary velocity to the values when porosity is equal to zero. Matrix velocity and density values were introduced into the formulas used to calculate porosity. Anisotropy analysis was made on the basis of elastic wave velocities measured on cores cut in two perpendicular directions. This allowed for identification of fractures in rocks. Results showed that by comparing various petrophysical parameters it was possible to get better information about reservoir properties of aquifers.

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.

Thermoelastic Properties of (Mg,Fe)SiO3 Perovskite

2002 ◽  
Vol 718 ◽  
Author(s):  
Boris Kiefer ◽  
Lars Stixrude
Keyword(s):  
Elastic Wave ◽  
Elastic Properties ◽  
Solid Solutions ◽  
Elastic Constants ◽  
Lower Mantle ◽  
High Pressures ◽  
Thermoelastic Properties ◽  
Wave Velocities ◽  
Lateral Variations ◽  
Iron Bearing

AbstractMagnesium rich (Mg1-x,Fex perovskite is thought to be the most abundant mineral in the earth's lower mantle between 660 km and 2900 km depth. We discuss (mg,Fe) solid solutions and their elastic properties at lower mantle pressures. The diffrences of the elastic constants between the Mg-endmember and the iron bearing perovskite with x=0.25 are used to predict the compositional contribution to lateral variations of elastic wave-velocities at high pressures. These predictions are compared and discussed in the context of seismic observations.

Prediction of elastic‐wave velocities in sandstones using structural models

Geophysics ◽  
1995 ◽  
Vol 60 (2) ◽  
pp. 437-446 ◽  
Author(s):  
Steven Bryant ◽  
Sue Raikes
Keyword(s):  
Elastic Wave ◽  
Structural Models ◽  
Void Space ◽  
Wave Velocities ◽  
Shear Wave Velocities ◽  
Aspect Ratios ◽  
Diagenetic Processes ◽  
Geological Models ◽  
Microstructural Data ◽  
Good Agreement

Elastic‐wave propagation in fluid‐saturated sandstones depends upon two sets of rock features: (1) the volume fractions and elastic constants of the rock constituents (quartz, clay, water, etc.) and (2) microstructural geometry (grain contacts, pore aspect ratios). While the former data are usually obtainable, the latter are relatively inaccessible. We present a new method for determining microstructural data using idealized but physically representative models of sandstone. The key to the method is the simulation of certain depositional and diagenetic processes in a manner that completely specifies the geometry of the resulting models. Hence, the geometric features of the grain space and void space required for various theories of elastic propagation can be calculated directly from the models. We find good agreement between predictions and measurements of compressional‐ and shear‐wave velocities in both clean and clay‐bearing saturated sandstones. In contrast with previous efforts at predicting velocities, we use no adjustable parameters and require no additional measurements on samples, such as dry velocities or analysis of thin‐section images. The results suggest that it is feasible to predict elastic velocities directly from geological models in the absence of rock samples.

Anisotropy of elastic wave velocities in deformed shales: Part 1 — Experimental results

Geophysics ◽  
2008 ◽  
Vol 73 (5) ◽  
pp. D75-D89 ◽  
Author(s):  
Joël Sarout ◽  
Yves Guéguen
Keyword(s):  
Elastic Wave ◽  
Wave Velocity ◽  
Elastic Anisotropy ◽  
Ambient Pressure ◽  
Transversely Isotropic ◽  
Elastic Wave Velocity ◽  
Velocity Measurements ◽  
Wave Velocities ◽  
In Situ Conditions ◽  
Triaxial Cell

Elastic wave velocity measurements in the laboratory are used to assess the evolution of the microstructure of shales under triaxial stresses, which are representative of in situ conditions. Microstructural parameters such as crack aperture are of primary importance when permeability is a concern. The purpose of these experiments is to understand the micromechanical behavior of the Callovo-Oxfordian shale in response to external perturbations. The available experimental setup allows for the continuous, simultaneous measurement of five independent elastic wave velocities and two directions of strain (axial and circumferential), performed on the same cylindrical rock sample during deformation in an axisymmetric triaxial cell. The main results are (1) identification of the complete tensor of elastic moduli of the transversely isotropic shales using elastic wave velocity measurements, (2) assessment of the evolution of these moduli under triaxial loading, and (3) assessment of the evolution of the elastic anisotropy under loading in terms of Thomsen’s parameters. This last outcome allows us to use the anisotropy of the elastic properties of this rock as an indicator of the evolution of its microstructure. In particular, [Formula: see text] in the dry case decreases from 0.5 (ambient pressure) toward 0.37 [Formula: see text], while [Formula: see text] and [Formula: see text] are almost insensitive to pressure. In the wet case, [Formula: see text] decreases from 0.3 (ambient pressure) toward 0.2 [Formula: see text]. Deviatoric stresses have a strong effect on [Formula: see text], [Formula: see text], and [Formula: see text] variations. In this case, [Formula: see text] drops (both for the dry and wet conditions) when failure is approached.

scholarly journals Velocity-Porosity-Mineralogy Model for Unconventional Shale and Its Applications to Digital Rock Physics

2021 ◽  
Vol 8 ◽  
Author(s):  
Jack Dvorkin ◽  
Joel Walls ◽  
Gabriela Davalos
Keyword(s):  
Elastic Wave ◽  
Elastic Properties ◽  
Wave Velocity ◽  
Solid Phase ◽  
Rock Physics ◽  
Elastic Wave Velocity ◽  
Mathematical Form ◽  
Critical Porosity ◽  
Physics Model ◽  
Rock Physics Model

By examining wireline data from Woodford and Wolfcamp gas shale, we find that the primary controls on the elastic-wave velocity are the total porosity, kerogen content, and mineralogy. At a fixed porosity, both Vp and Vs strongly depend on the clay content, as well as on the kerogen content. Both velocities are also strong functions of the sum of the above two components. Even better discrimination of the elastic properties at a fixed porosity is attained if we use the elastic-wave velocity of the solid matrix (including kerogen) of rock as the third variable. This finding, fairly obvious in retrospect, helps combine all mineralogical factors into only two variables, Vp and Vs of the solid phase. The constant-cement rock physics model, whose mathematical form is the modified lower Hashin-Shtrikman elastic bound, accurately describes the data. The inputs to this model include the elastic moduli and density of the solid component (minerals plus kerogen), those of the formation fluid, the differential pressure, and the critical porosity and coordination number (the average number of grain-to-grain contacts at the critical porosity). We show how this rock physics model can be used to predict the elastic properties from digital images of core, as well as 2D scanning electron microscope images of very small rock fragments.

Elastic Properties of Low Density Core (LDC) Ti-6Al-4V Sandwich Cores

1998 ◽  
Vol 521 ◽  
Author(s):  
D. T. Queheillalt ◽  
H. N. G. Wadley ◽  
D. S. Schwartz
Keyword(s):  
Elastic Properties ◽  
Volume Fraction ◽  
Analytical Models ◽  
Low Density ◽  
Ultrasonic Methods ◽  
Wave Velocities ◽  
Shear Wave Velocities ◽  
High Temperature Anneal ◽  
Porous Microstructure ◽  
Gas Expansion

ABSTRACTLightweight, structurally efficient low density core (LDC) sandwich structures can be produced by entrapping argon gas within a finely dispersed distribution of pores in a microstructure and using a high temperature anneal to cause pore growth by gas expansion. This results in a porous microstructure with a relative density as low as ∼0.70. Laser ultrasonic methods have been used to measure the longitudinal and shear wave velocities and hence the elastic properties of LDC Ti-6Al-4V cores prior to, and after gas expansion treatments of up to 48 hr at 920°C. The data was compared with several analytical models for predicting the volume fraction of porosity dependent elastic properties of porous materials.

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