Seismic signatures of partial saturation on acoustic borehole modes

Geophysics ◽  
2007 ◽  
Vol 72 (2) ◽  
pp. E77-E86 ◽  
Author(s):  
Gabriel Chao ◽  
D. M. J. Smeulders ◽  
M. E. H. van Dongen
Keyword(s):  
Bubble Size ◽  
Strong Dependence ◽  
Gas Bubbles ◽  
Oscillatory Behavior ◽  
Stoneley Wave ◽  
Biot Theory ◽  
Porous Rocks ◽  
Mud Cake ◽  
Attenuation And Dispersion

We present an exact theory of attenuation and dispersion of borehole Stoneley waves propagating along porous rocks containing spherical gas bubbles by using the Biot theory. An effective frequency-dependent fluid bulk modulus is introduced to describe the dynamic (oscillatory) behavior of the gas bubbles. The model includes viscous, thermal, and radiation damping. It is assumed that the gas pockets are larger than the pore size, but smaller than the wavelengths involved (mesoscopic inhomogeneity). A strong dependence of the attenuation of the Stoneley wave on gas fraction and bubble size is found. Attenuation increases with gas fraction over the complete range of studied frequencies [Formula: see text]. The dependence of the phase velocity on the gas fraction and bubble size is restricted to the lower frequency range. These results indicate that the interpretation of Stoneley wave properties for the determination of, for example, local permeability formation is not straightforward and could be influenced by the presence of gas in the near-wellbore zone. When mud-cake effects are included in the model, the same observations roughly hold, though dependence on the mud-cake stiffness is quite complex. In this case, a clear increase of the damping coefficient with saturation is predicted only at relatively high frequencies.

Attenuation and dispersion of compressional waves in fluid‐filled porous rocks with partial gas saturation (White model)—Part I: Biot theory

Geophysics ◽  
1979 ◽  
Vol 44 (11) ◽  
pp. 1777-1788 ◽  
Author(s):  
N. C. Dutta ◽  
H. Odé
Keyword(s):  
Seismic Waves ◽  
Equations Of Motion ◽  
Fluid Pressure ◽  
Present Theory ◽  
Biot Theory ◽  
Type I ◽  
Porous Rocks ◽  
Water Contact ◽  
Coupled Equations ◽  
Attenuation And Dispersion

An exact theory of attenuation and dispersion of seismic waves in porous rocks containing spherical gas pockets (White model) is presented using the coupled equations of motion given by Biot. Assumptions made are (1) the acoustic wavelength is long with respect to the distance between gas pockets and their size, and (2) the gas pockets do not interact. Thus, the present theory essentially is quite similar to that proposed by White (1975), but the problem of the radially oscillating gas pocket is solved in a more rigorous manner by means of Biot’s theory (1962). The solid‐fluid coupling is automatically included, and the model is solved as a boundary value problem requiring all radial stresses and displacements to be continuous at the gas‐brine interface. Thus, we do not require any assumed fluid‐pressure discontinuity at the gas‐water contact, such as the one employed by White (1975). We have also presented an analysis of all of the field variables in terms of Biot’s type I (the classical compressional) wave and, type II (the diffusion) wave. Our quantitative results are presented in Dutta and Odé (1979, this issue).

Interfacial dynamics of stationary gas bubbles in flows in inclined tubes

1999 ◽  
Vol 398 ◽  
pp. 225-244 ◽  
Author(s):  
DANIEL P. CAVANAGH ◽  
DAVID M. ECKMANN
Keyword(s):  
Pressure Gradient ◽  
Bubble Size ◽  
Contact Angle Hysteresis ◽  
Gas Bubbles ◽  
Solid Material ◽  
Contact Forces ◽  
Tube Material ◽  
Experimental Conditions ◽  
Axial Pressure Gradient ◽  
Inclination Angles

We have experimentally examined the effects of bubble size (0.4 [les ] λ [les ] 2.0), inclination angle (0° [les ] α [les ] 90°), and tube material on suspended gas bubbles in flows in tubes for a range of Weber (0 [les ] We [les ] 3.6), Reynolds (0 [les ] Re [les ] 1200), and Froude (0 [les ] Frα [les ] 1) numbers. Flow rates and associated pressure differences which allow the suspension of bubbles in glass and acrylic tubes are measured. Due to contact angle hysteresis, bubbles which dry the tube wall (i.e. form a gas–solid interface) may remain suspended over a range of flows while non-drying bubbles remain stationary for a single flow rate depending on experimental conditions. Stationary bubbles increase the axial pressure gradient with larger bubbles and steeper inclination angles leading to the greatest increase in the pressure gradient. Both the suspension flow range and pressure difference modifications are strongly dependent upon gas/liquid/solid material interactions. Stronger contact forces, i.e. smaller spreading coefficients, cause dried bubbles in acrylic tubes to remain stationary over a wider range of suspension flows than bubbles in glass tubes. Bubble deformation is governed by the interaction of interfacial, contact, and flow-derived forces. This investigation reveals the importance of bubble size, tube inclination, and tube material on gas bubble suspension.

Influence of bubble size and blood perfusion on absorption of gas bubbles in tissues

1969 ◽  
Vol 7 (1) ◽  
pp. 111-121 ◽  
Author(s):  
Hugh D. Van Liew ◽  
Michael P. Hlastala
Keyword(s):  
Bubble Size ◽  
Gas Bubbles ◽  
Blood Perfusion

Study on the High Shear Degassing Process with Water Simulation

2015 ◽  
Vol 1120-1121 ◽  
pp. 1214-1219
Author(s):  
Yi Yao Kang ◽  
Yue Lin ◽  
Xu Dong Liu ◽  
Chao Sun ◽  
Sen Sen Yuan ◽  
...  
Keyword(s):  
Bubble Size ◽  
Aluminium Alloys ◽  
High Efficiency ◽  
Rotation Speed ◽  
Gas Bubbles ◽  
Inert Gas ◽  
High Shear ◽  
Gas Porosity ◽  
Water Simulation ◽  
Proper Rotation

Hydrogen as the main cause of the gas porosity in aluminium alloys should be removed before casting. The degassing process with intensive melt shearing shows a high efficiency. In the present work, the water simulation was used to study the high shear degassing process and the effect of rotation speed on the size and distribution of inert gas bubbles. The results show that with the increase of rotation speed, the bubble size decreases and the affected region becomes larger. The proper rotation speed of the rotor for the rotor-stator high shear degassing process is 5000-6000 RPM.

Climatology of Cyclone Size Characteristics and Their Changes during the Cyclone Life Cycle

2007 ◽  
Vol 135 (7) ◽  
pp. 2568-2587 ◽  
Author(s):  
Irina Rudeva ◽  
Sergey K. Gulev
Keyword(s):  
Life Cycle ◽  
Quantitative Estimation ◽  
Strong Dependence ◽  
Development Stage ◽  
Effective Radius ◽  
Central Pressure ◽  
Sea Level Pressure ◽  
Size Evolution ◽  
Cyclone Tracking

Abstract Climatology of the atmospheric cyclone sizes and their change over the cyclone life cycle is analyzed on the basis of tracking 57 yr of NCEP–NCAR reanalysis sea level pressure data over the Northern Hemisphere. To quantify the atmospheric cyclone sizes a coordinate transform was used, which allows for the collocation of the cyclone center with the virtual pole and for the establishment of a unique coordinate system for the further determination of cyclone geometry. This procedure was incorporated into a numerical cyclone tracking scheme and provided quantitative estimation of cyclone geometry at every stage of the cyclone development. Climatological features of the distribution of the cyclone size characteristics (effective radius, asymmetry) are considered for the cyclones with different central pressure, deepening rate, and lifetime. Mean effective cyclone radius may experience significant changes, ranging from 300–400 km over the continents to more than 900 km over the oceans. There is found to be a strong dependence of the cyclone effective radius on the cyclone lifetime and intensity, implying the largest cyclone sizes for the most intense and long-living transients. Analysis of size changes during the cyclone life cycle implies that the cyclone radius increases during the development stage from 50% to 150%. Size evolution during the cyclone life cycle implies a universal dependence of the normalized cyclone effective radius and the normalized cyclone age. The actual maximum cyclone radius can be determined from these two nondimensional parameters and cyclone central pressure. Further application of the analysis of cyclone size and shape are discussed.

Further discussion on attenuation and dispersion of electromagnetic wave propagation in fluid‐saturated porous rocks and applications to dielectric‐constant well logging

Geophysics ◽  
1983 ◽  
Vol 48 (10) ◽  
pp. 1373-1380 ◽  
Author(s):  
H. Pascal
Keyword(s):  
Dielectric Constant ◽  
Wave Propagation ◽  
Electromagnetic Wave ◽  
Electromagnetic Wave Propagation ◽  
Phase Model ◽  
Phase System ◽  
Porous Rocks ◽  
Two Phase ◽  
Advantages And Disadvantages ◽  
Attenuation And Dispersion

This paper presents a more detailed analysis of some basic problems of electromagnetic wave propagation through a porous medium saturated with fluid, associated directly with quantitative interpretation of dielectric constant logging. The advantages and disadvantages of a new approach, in which fluid‐saturated porous rock is considered as a two‐phase system, are discussed and compared with those obtained from the single‐phase model. It is shown that the two‐phase model may provide a better interpretation of dielectric constant logging.

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