Comments on “On pore fluid viscosity and the wave properties of saturated granular materials including marine sediments” [J. Acoust. Soc. Am. 122, 1486–1501 (2007)]

2010 ◽  
Vol 127 (4) ◽  
pp. 2095-2098 ◽  
Author(s):  
Nicholas P. Chotiros ◽  
Marcia J. Isakson
Keyword(s):  
Granular Materials ◽  
Marine Sediments ◽  
Pore Fluid ◽  
Fluid Viscosity ◽  
Wave Properties

A dynamic elastic model for squirt-flow effect and its application on fluid-viscosity-associated velocity dispersion in reservoir sandstones

Geophysics ◽  
2020 ◽  
Vol 85 (4) ◽  
pp. MR201-MR212
Author(s):  
Zhi-Qiang Yang ◽  
Tao He ◽  
Chang-Chun Zou
Keyword(s):  
Velocity Dispersion ◽  
Pore Space ◽  
Pore Fluid ◽  
Quantitative Prediction ◽  
Elastic Model ◽  
Fluid Viscosity ◽  
Porous Rocks ◽  
S Wave ◽  
Flow Effect ◽  
Reservoir Sandstones

Velocity dispersion is a common phenomenon for fluid-charged porous rocks and carries important information on the pore structure and fluid in reservoir rocks. Previous ultrasonic experiments had measured more significant non-Biot velocity dispersion on saturated reservoir sandstones with increasing pore-fluid viscosity. Although wave-induced local squirt-flow effect could in theory cause most of the non-Biot velocity dispersion, its quantitative prediction remains a challenge. Several popular models were tested to predict the measured velocities under undrained conditions, but they either underestimated the squirt-flow effect or failed to simultaneously satisfy P- and S-wave velocity dispersions (especially for higher viscosity fluids). Based on the classic double-porosity theory that pore space is comprised of mainly stiff/Biot’s porosity and minor compliant porosity, an effective “wet frame” was hypothesized to account for the squirt-flow effect, whose compliant pores are filled with a hypothesized fluid with dynamic modulus. A new dynamic elastic model was then introduced by extending Biot theory to include the squirt-flow effect, after replacing the dry-frame bulk/shear moduli with their wet-frame counterparts. In addition to yielding better velocity predictions for P- and S-wave measurements of different fluid viscosities, the new model is also more applicable because its two key tuning parameters (i.e., the effective aspect ratio and porosity of compliant pores) at in situ reservoir pressure could be constrained with laboratory velocity measurements associated with pore-fluid viscosities.

scholarly journals Tortuosity and the Averaging of Microvelocity Fields in Poroelasticity

2013 ◽  
Vol 80 (2) ◽  
Author(s):  
M. F. Souzanchi ◽  
L. Cardoso ◽  
S. C. Cowin
Keyword(s):  
Porous Media ◽  
Kinetic Energy ◽  
Energy Loss ◽  
Cancellous Bone ◽  
Quantitative Measure ◽  
Pore Fluid ◽  
Fluid Viscosity ◽  
Anisotropic Porous Media ◽  
Pore Architecture ◽  
Kinetic Energy Loss

The relationship between the macro- and microvelocity fields in a poroelastic representative volume element (RVE) has not being fully investigated. This relationship is considered to be a function of the tortuosity: a quantitative measure of the effect of the deviation of the pore fluid streamlines from straight (not tortuous) paths in fluid-saturated porous media. There are different expressions for tortuosity based on the deviation from straight pores, harmonic wave excitation, or from a kinetic energy loss analysis. The objective of the work presented is to determine the best expression for tortuosity of a multiply interconnected open pore architecture in an anisotropic porous media. The procedures for averaging the pore microvelocity over the RVE of poroelastic media by Coussy and by Biot were reviewed as part of this study, and the significant connection between these two procedures was established. Success was achieved in identifying the Coussy kinetic energy loss in the pore fluid approach as the most attractive expression for the tortuosity of porous media based on pore fluid viscosity, porosity, and the pore architecture. The fabric tensor, a 3D measure of the architecture of pore structure, was introduced in the expression of the tortuosity tensor for anisotropic porous media. Practical considerations for the measurement of the key parameters in the models of Coussy and Biot are discussed. In this study, we used cancellous bone as an example of interconnected pores and as a motivator for this study, but the results achieved are much more general and have a far broader application than just to cancellous bone.

Effects of capillary number, Bond number, and gas solubility on water saturation of sand specimens

2013 ◽  
Vol 50 (2) ◽  
pp. 133-144 ◽  
Author(s):  
Bruce L. Kutter
Keyword(s):  
Capillary Number ◽  
Water Saturation ◽  
Fluid Pressure ◽  
Infiltration Rate ◽  
Capillary Forces ◽  
Bond Number ◽  
Pore Fluid ◽  
Degree Of Saturation ◽  
Fluid Viscosity ◽  
Viscous Forces

To better understand how to prepare completely water-saturated specimens or centrifuge models from dry sand, the mechanisms of the infiltration and filling of pores in sand are studied. Complete saturation has been shown by others to be especially important in studies involving the triggering of liquefaction. This paper discusses how the degree of saturation obtained during infiltration increases with the “Bond number”, Bo (ratio of body forces and capillary forces), and the “capillary number”, Ca (ratio of viscous forces and capillary forces), as well as the solubility of gas bubbles in the pore fluid. Bo is varied by changing the particle size, fluid density, and centrifugal acceleration. Ca is varied by changing the fluid viscosity and infiltration rate. The dissolution of gas is encouraged by replacing pore air by CO2 (56 times more soluble in water than N2), by de-airing the liquid prior to infiltration or by increasing the pore fluid pressure after infiltration. Infiltration experiments performed at 1g and in a centrifuge are presented. A new technique for measuring the degree of saturation is also presented. Quantitative pressure–saturation relations are presented for different gasses, illustrating the importance of replacement of air by CO2. Spinning a specimen in a centrifuge during infiltration is also useful for speeding up the saturation process and for achieving higher degrees of saturation.

Effects of in situ permeability on the propagation of Stoneley (tube) waves in a borehole

Geophysics ◽  
1987 ◽  
Vol 52 (9) ◽  
pp. 1279-1289 ◽  
Author(s):  
C. H. Cheng ◽  
Zhang Jinzhong ◽  
Daniel R. Burns
Keyword(s):  
Phase Velocity ◽  
Wave Amplitude ◽  
Pore Fluid ◽  
Stoneley Wave ◽  
Published Data ◽  
Intrinsic Attenuation ◽  
Wave Phase ◽  
In Situ Permeability ◽  
Wave Properties

We investigated the theoretical relationship between propagation characteristics of Stoneley (tube) waves in a borehole and in situ permeability by using a modified formulation of a borehole model with a formation that behaves as a Biot porous medium. We found that Stoneley‐wave attenuation and phase‐velocity dispersion increased with increasing permeability and porosity, and decreased with increasing frequency. In rocks with low to medium permeabilities (less than 100 mD), variations in formation velocity and attentuation were major contributors to variations in Stoneley‐wave properties at normal logging frequencies. However, in high‐permeability rocks (greater than 100 mD), coupling between the borehole and pore fluids associated with in situ permeability was more important than lithological changes in controlling Stoneley‐wave properties. Pore‐fluid viscosity had an effect on Stoneley‐wave propagation equal but opposite to permeability, and hence must he taken into account. We compared our theoretical results with published data on core permeability and Stoneley‐wave phase velocities and amplitudes. The Stoneley‐wave amplitude was more sensitive to the permeability of the formation than Stoneley‐wave phase velocity. By assuming an appropriate average value of intrinsic attenuation, we obtained reasonable agreements between theory and the published data. We conclude that relative permeability within a formation can be determined quite well using Stoneley‐wave amplitude and phase velocity, but absolute permeability determination requires accurate measurements of parameters such as the intrinsic attenuation of the formation and the viscosity and compressibility of the pore fluid.

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