Wave Velocities in Sediments

1990 ◽  
Vol 195 ◽  
Author(s):  
Dominique Marion ◽  
Amos Nur ◽  
Hezhu Yin
Keyword(s):  
Pore Space ◽  
Low Frequency ◽  
Clay Content ◽  
Velocity Versus ◽  
Critical Porosity ◽  
Porous Sandstone ◽  
Linear Fit ◽  
Compressional Velocity

ABSTRACTSystematic relations between porosity and compressional velocity Vp in the three component (sand, grains, clay and brine) systems (1) porous sandstone, (2) sands, and (3) suspensions, were obtained using experimental data and models. In Cemented Shaley Sandstones Vp was found to correlate linearly with porosity and clay content. The velocities in clean sandstones are about 7% higher than those predicted by the linear fit, indicating that a small amount of clay significantly reduces the elastic moduli of sandstones.For uncemented shaley sand, a model for the dependence of sonic velocity and porosity on clay content and compaction was developed for sand with clay dispersed in the pore space and for shale with suspened sand grains. The model closely mimics the experimentally observed minimum for porosity and the peak in velocity versus clay content. The results explain much of the scatter in velocity data in-situ. Velocity in suspensions at ϕ = 39% of grains in brine is close to values predicted by the Reuss (Isostress) average. Velocity dispersion, as suggested by Biot (1956 a,b) is calculated and observed in coarser sediments such as sand, whereas velocities in the finer clay and silt follow Biot's low frequency value.In total, our results provide the complete dependence of velocity on porosity in brine saturated sediment with clays, ranging from pure quartz to pure clay and water. Our results also highlight the crucial role of the critical porosity ϕ at about 39%, and the transition from cemented to uncemented sands.

Compressional velocity and porosity in sand‐clay mixtures

Geophysics ◽  
1992 ◽  
Vol 57 (4) ◽  
pp. 554-563 ◽  
Author(s):  
D. Marion ◽  
A. Nur ◽  
H. Yin ◽  
D. Han
Keyword(s):  
Pore Space ◽  
Clay Content ◽  
Geometrical Model ◽  
Velocity Versus ◽  
Filling Material ◽  
Ottawa Sand ◽  
Unconsolidated Sand ◽  
Confining Pressures ◽  
Clay Matrix ◽  
Compressional Velocity

Laboratory measurements of porosity and compressional velocity were conducted on unconsolidated brine saturated clean Ottawa sand, pure kaolinite, and their mixtures at various confining pressures. A peak in P velocity versus clay content in unconsolidated sand‐clay mixtures at 40 percent clay by weight was found. The peak in velocity is 20–30 percent higher than for either pure clay or clean sand. A minimum in porosity versus clay content at 20–40 percent clay by weight is also observed. Such behavior is explained using a micro‐geometrical model for mixtures of sand and clay in which two classes of sediments are considered: (1) sands and shaley sands, in which clay is dispersed in the pore space of load bearing sand and thus reduces porosity and increases the elastic moduli of the pore‐filling material and (2) shales and sandy shales, in which sand grains are dispersed in a clay matrix. For these sediments, the model reproduces the extrema in velocity and porosity and accounts for much of the scatter in the velocity‐porosity relationship.

Predicting lithology and transport properties from acoustic velocities based on petrophysical classification of siliciclastics

Geophysics ◽  
1994 ◽  
Vol 59 (3) ◽  
pp. 420-427 ◽  
Author(s):  
L. Vernik
Keyword(s):  
Transport Properties ◽  
Velocity Ratio ◽  
Clay Content ◽  
Unconsolidated Sediments ◽  
Velocity Versus ◽  
Critical Porosity ◽  
Porosity Reduction ◽  
Lithology Prediction ◽  
Acoustic Velocities

Based on the recently developed petrophysical classification of siliciclastics, which takes into account the amount of the volumetric clay content C and textural position of clay, it is shown that acoustic velocities can be fairly accurate tools in predicting lithology, porosity, and ultimately, transport properties of these rocks. Four major petrophysical groups of carbonate‐ and organic‐poor siliciclastics are distinguished: (1) clean arenites (C < 2 percent), (2) arenites and arkoses (C = 2–15 percent), (3) wackes (C = 15–35 percent), and (4) shales (C > 35 percent). The compressional velocity versus porosity relation for consolidated rocks in each of these groups is found to be linear with very high correlation coefficients. This allows for remarkably accurate porosity estimates or lithology prediction in consolidated siliciclastics from acoustic velocities compared to the widely used time average (Wyllie) equation or its improved modification (Raymer equations), both of which neglect textural factors, or recently proposed relations based on the critical porosity concept. The transforms proposed display fundamental trends subject to only a second‐order regional effects, such as details of mineralogy, grain size distribution, and authigenic clay development. These trends primarily reflect the processes of chemical diagenesis, including pressure solution, cementation, and mineral phase transformation. The processes of lithification of unconsolidated sediments by physical compaction and initial cementation are characterized by a steeper slope of the velocity‐porosity transform because of a more pronounced velocity increase compared to the porosity reduction at this stage. The use of the [Formula: see text] ratio versus velocity relation for lithology prediction is limited compared to the [Formula: see text] versus porosity plots; however, if both porosity and lithology are unknown, the velocity ratio can still be used for discriminating between predominantly grain‐supported reservoir rocks (clean arenite, arenite and arkose) and clay matrix‐supported (wacke, shale) rocks. Finally, a strong correlation between porosity and permeability of clean arenites is weakened somewhat in arenites. Nonetheless, even in the latter case, an order of magnitude accuracy in permeability assessment based on porosity can be achieved.

scholarly journals Comparative Expression of P53 and Survivin Proteins in Phenylhydrazine-Induced Colon Cancer of Rats and the Role of Electromagnetic Field and Broccoli Extract

2021 ◽  
Author(s):  
Aziz Awaad ◽  
Mohamed A. Adly ◽  
Medhat A. Abd ellatef ◽  
Moshira M. Foad
Keyword(s):  
Colon Cancer ◽  
Electromagnetic Field ◽  
Combined Therapy ◽  
Low Frequency ◽  
Survivin Expression ◽  
Cancer Model ◽  
Beneficial Effects ◽  
Anti Cancer

Abstract Cancer constitutes as one of the most serious causes of death worldwide. For example, colon cancer is the second-most dangerous type of cancer, affecting both men and women. Recently, the application of electromagnetic field (EMF) in the treatment of cancer whether alone or in combination with other anti-cancer materials seems to be a promising therapy. Furthermore, broccoli extract which is rich with sulforaphane (sulfur-rich compound) previously used as one of anti-cancer materials. In this context, the current study aimed to investigate the potential beneficial effects of extremely low frequency-EMF (ELF-EMF) application alone and in combination with broccoli extract in the treatment and protection from cancer in phenylhydrazine (PHZ)-induced colon cancer model. To achieve our aims, the histolopathological abnormalities were investigated histologically and the comparative expression of P53 and survivin proteins were investigated immunohistochemically. This report revealed that PHZ injection was able to induce carcinogenicity in the large intestine of rats especially colon. The PHZ-injected group showed abnormal, biochemical, histological and immunohistochemical parameters. Histologically, the treated colon showed high-grade dysplastic lesions that are further considered as carcinoma-in-situ. The expression of P53 in the crypt of colon decreased significantly in the epithelial cells and lamina propria stroma. Contradictory, survivin expression increased in the same regions after animal exposed to PHZ. However, exposure of PHZ-injected animals to ELF-EMF or broccoli extract separately didn't ameliorate the abnormalities produced by PHZ completely. Interestingly, the combination between ELF-EMF and broccoli extract significantly mitigated the effects of PHZ and succeeded in suppressing tumor progression and normalize the expression of P53 and survivin expressions. This study provided important information about expression of important proteins during cancer stages and the role of combined therapy using EMFs and broccoli extract. Furthermore, the expression changes of P53 and survivin proteins might be used as markers in cancer diagnosis and treatment progress.

Role of cast-in situ slabs in RC frames under low frequency cyclic load

2014 ◽  
Vol 59 ◽  
pp. 28-38 ◽  
Author(s):  
Ning Ning ◽  
Wenjun Qu ◽  
Peng Zhu
Keyword(s):  
Cyclic Load ◽  
Low Frequency ◽  
Rc Frames

On the role of microgeometry in conductivity substitution

Geophysics ◽  
2020 ◽  
Vol 85 (3) ◽  
pp. MR117-MR127
Author(s):  
Priyanka Dutta ◽  
Gary Mavko ◽  
Chen Guo
Keyword(s):  
Effective Conductivity ◽  
Pore Space ◽  
Clay Content ◽  
Fluid Phase ◽  
Two Phase ◽  
Archie’S Law ◽  
Phase Conductivity ◽  
Rock Microstructure ◽  
Conductivity Contrast

Conductivity substitution is the process of predicting the change in the effective electrical conductivity of a rock upon a change in conductivity of the mineral or fluid phase. Conductivity substitution is nonunique — only a range of conductivities can be predicted from knowledge of the initial effective conductivity, the porosity, and the initial and final compositions. The precise change depends strongly on the rock microstructure, which is seldom adequately known. Rigorous bounds on the change in effective conductivity upon changes in the phase conductivities for two-phase isotropic composites are used to gain insights into the roles of microgeometry and phase conductivity contrast. When the conductivity contrast between phases is high, the conductivity substitution predicted by Archie’s law corresponds approximately to the upper bound on the change of conductivity upon substitution. Inclusion modeling suggests that vuggy, highly tortuous, or partially disconnected pore space could account for conductivity changes smaller than those predicted by Archie’s law. Substitution behavior computed analytically for known microgeometries correlates with measures of microgeometry, including the fraction of connected fluid phase and variance of electric field strength in each phase. Comparison of the conductivity substitution bounds with brine-saturated sandstone data reveals that the position of measured data with respect to the conductivity substitution bounds can be indicative of the effective clay content. The bounds provide a template for better prediction of effective conductivity if we have at least some knowledge of the pore microstructure. Similarly, multiple conductivity measurements on the same rock might be used to extract more information about the rock and pore space properties than is possible with only a single measurement.

Calculation-and-experimental estimation of the role of the frequency ratio in changing the endurance at two-frequency deformation modes

2019 ◽  
Vol 85 (1(I)) ◽  
pp. 64-71 ◽  
Author(s):  
M. M. Gadenin
Keyword(s):  
High Frequency ◽  
Experimental Studies ◽  
Low Frequency ◽  
Reduction Factor ◽  
Single Frequency ◽  
Cyclic Loads ◽  
Small Ratio ◽  
Harmonic Components ◽  
Deformation Modes

The cycle configuration at two-frequency loading regimes depends on the number of parameters including the absolute values of the frequencies and amplitudes of the low-frequency and high-frequency loads added during this mode, the ratio of their frequencies and amplitudes, as well as the phase shift between these harmonic components, the latter having a significant effect only with a small ratio of frequencies. Presence of such two-frequency regimes or service loading conditions for parts of machines and structures schematized by them can significantly reduce their endurance. Using the results of experimental studies of changes in the endurance of a two-frequency loading of specimens of cyclically stable, cyclically softened and cyclically hardened steels under rigid conditions we have shown that decrease in the endurance under the aforementioned conditions depends on the ratio of frequencies and amplitudes of operation low-frequency low-cycle and high-frequency vibration stresses, and, moreover, the higher the level of the ratios of amplitudes and frequencies of those stacked harmonic processes of loading the greater the effect. It is shown that estimation of such a decrease in the endurance compared to a single frequency loading equal in the total stress (strains) amplitudes can be carried out using an exponential expression coupling those endurances through a parameter (reduction factor) containing the ratio of frequencies and amplitudes of operation cyclic loads and characteristic of the material. The reduction is illustrated by a set of calculation-experimental curves on the corresponding diagrams for each of the considered types of materials and compared with the experimental data.

{10-12} Twinning Mechanism During In Situ Micro-Tensile Loading of Pure Mg: Role of Basal Slip and Twin-Twin Boundary Interaction

2020 ◽  
Author(s):  
Nicolò Maria della Ventura ◽  
Szilvia Kalácska ◽  
Daniele Casari ◽  
Thomas Edward James Edwards ◽  
Johann Michler ◽  
...  
Keyword(s):  
Twin Boundary ◽  
Basal Slip ◽  
Tensile Loading ◽  
Boundary Interaction

The role of (bio)surfactant sorption in promoting the bioavailability of nutrients localized at the solid-water interface

1999 ◽  
Vol 39 (7) ◽  
pp. 91-98 ◽  
Author(s):  
Ryan N. Jordan ◽  
Eric P. Nichols ◽  
Alfred B. Cunningham
Keyword(s):  
Mass Transfer ◽  
Cell Membrane ◽  
Substrate Concentration ◽  
Water Interface ◽  
Industrial Systems ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
Surfactant Sorption

Bioavailability is herein defined as the accessibility of a substrate by a microorganism. Further, bioavailability is governed by (1) the substrate concentration that the cell membrane “sees,” (i.e., the “directly bioavailable” pool) as well as (2) the rate of mass transfer from potentially bioavailable (e.g., nonaqueous) phases to the directly bioavailable (e.g., aqueous) phase. Mechanisms by which sorbed (bio)surfactants influence these two processes are discussed. We propose the hypothesis that the sorption of (bio)surfactants at the solid-liquid interface is partially responsible for the increased bioavailability of surface-bound nutrients, and offer this as a basis for suggesting the development of engineered in-situ bioremediation technologies that take advantage of low (bio)surfactant concentrations. In addition, other industrial systems where bioavailability phenomena should be considered are addressed.

Sign in / Sign up

Export Citation Format

Share Document