scholarly journals Including poroelastic effects in the linear slip theory

Geophysics ◽  
2015 ◽  
Vol 80 (2) ◽  
pp. A51-A56 ◽  
Author(s):  
J. Germán Rubino ◽  
Gabriel A. Castromán ◽  
Tobias M. Müller ◽  
Leonardo B. Monachesi ◽  
Fabio I. Zyserman ◽  
...  
Keyword(s):  
Viscous Friction ◽  
Seismic Wave Propagation ◽  
Seismic Attenuation ◽  
Porous Rocks ◽  
Compliance Matrix ◽  
Frequency Dependent ◽  
Attenuation Mechanism ◽  
Wave Induced ◽  
Complex Valued ◽  
Good Agreement

Numerical simulations of seismic wave propagation in fractured media are often performed in the framework of the linear slip theory (LST). Therein, fractures are represented as interfaces and their mechanical properties are characterized through a compliance matrix. This theory has been extended to account for energy dissipation due to viscous friction within fluid-filled fractures by using complex-valued frequency-dependent compliances. This is, however, not fully adequate for fractured porous rocks in which wave-induced fluid flow (WIFF) between fractures and host rock constitutes a predominant seismic attenuation mechanism. In this letter, we develop an approach to incorporate WIFF effects directly into the LST for a 1D system via a complex-valued, frequency-dependent fracture compliance. The methodology is validated for a medium permeated by regularly distributed planar fractures, for which an analytical expression for the complex-valued normal compliance is determined in the framework of quasistatic poroelasticity. There is good agreement between synthetic seismograms generated using the proposed recipe and those obtained from comprehensive, but computationally demanding, poroelastic simulations.

Anisotropic P-SV-wave dispersion and attenuation due to inter-layer flow in thinly layered porous rocks

Geophysics ◽  
2011 ◽  
Vol 76 (3) ◽  
pp. WA135-WA145 ◽  
Author(s):  
Fabian Krzikalla ◽  
Tobias M. Müller
Keyword(s):  
Wave Attenuation ◽  
Fluid Pressure ◽  
Pore Fluid ◽  
P Wave ◽  
Angle Of Incidence ◽  
Porous Rocks ◽  
Frequency Dependent ◽  
Symmetry Properties ◽  
Wave Induced ◽  
Attenuation And Dispersion

Elastic upscaling of thinly layered rocks typically is performed using the established Backus averaging technique. Its poroelastic extension applies to thinly layered fluid-saturated porous rocks and enables the use of anisotropic effective medium models that are valid in the low- and high-frequency limits for relaxed and unrelaxed pore-fluid pressures, respectively. At intermediate frequencies, wave-induced interlayer flow causes attenuation and dispersion beyond that described by Biot’s global flow and microscopic squirt flow. Several models quantify frequency-dependent, normal-incidence P-wave propagation in layered poroelastic media but yield no prediction for arbitrary angles of incidence, or for S-wave-induced interlayer flow. It is shown that generalized models for P-SV-wave attenuation and dispersion as a result of interlayer flow can be constructed by unifying the anisotropic Backus limits with existing P-wave frequency-dependent interlayer flow models. The construction principle is exact and is based on the symmetry properties of the effective elastic relaxation tensor governing the pore-fluid pressure diffusion. These new theories quantify anisotropic P- and SV-wave attenuation and velocity dispersion. The maximum SV-wave attenuation is of the same order of magnitude as the maximum P-wave attenuation and occurs prominently around an angle of incidence of [Formula: see text]. For the particular case of a periodically layered medium, the theoretical predictions are confirmed through numerical simulations.

Macroscopic framework for viscoelasticity, poroelasticity, and wave-induced fluid flows — Part 1: General linear solid

Geophysics ◽  
2016 ◽  
Vol 81 (1) ◽  
pp. L1-L13 ◽  
Author(s):  
Igor B. Morozov ◽  
Wubing Deng
Keyword(s):  
Continuum Mechanics ◽  
Fluid Flows ◽  
Seismic Wave Propagation ◽  
Double Porosity ◽  
Pore Fluid ◽  
General Linear ◽  
Macroscopic Models ◽  
Wave Velocities ◽  
Wave Induced ◽  
Complex Valued

Field and laboratory observations of seismic wave propagation and attenuation are usually explained using the viscoelastic (VE) model and effective moduli. However, in sedimentary rocks, wave velocities and attenuation rates are dominated by pore-fluid effects, such as poroelasticity, squirt, and mesoscopic wave-induced fluid flows. Physically, such effects are significantly different from viscoelasticity, and the pore-fluid and VE phenomena are difficult to compare quantitatively without a common theoretical framework. We develop such a unified macroscopic framework that we call the general linear solid (GLS). The GLS is based on Lagrangian continuum mechanics, and it can be summarized as multiphase poroelasticity extended by solid and fluid viscosities. The formulation is carried out strictly in terms of continuum mechanics, measurable physical properties, and boundary conditions, from which the observable wave velocities and attenuation are predicted. Explicit differential equations are derived in matrix form, from which a variety of numerical modeling schemes can be obtained. A rigorous correspondence principle is formulated, in which viscosity effects contribute to complex-valued VE moduli, and Darcy friction lead to a complex-valued density matrix. Within the GLS framework, the viscoelasticity represents an end member characterized by zero Darcy-type friction, whereas the poroelasticity is an end member with zero solid viscosity. Transitions between these end members and their extensions yield macroscopic models of viscoporoelasticity, poroelasticity with multiple saturating fluids and double porosity, and poroelasticity with squirt flows. The approach is illustrated on models of layered poroelastic and viscoporoelastic media. Applications of the GLS framework are continued in part 2 of this study.

scholarly journals Experimental Methods for Measuring the Viscous Friction Coefficient in Hydraulic Spool Valves

2021 ◽  
Vol 13 (13) ◽  
pp. 7174
Author(s):  
Massimo Rundo ◽  
Paolo Casoli ◽  
Antonio Lettini
Keyword(s):  
Friction Coefficient ◽  
Viscous Friction ◽  
Experimental Tests ◽  
Experimental Methods ◽  
Displacement Transducer ◽  
A Posteriori ◽  
Displacement Control ◽  
Spool Valves ◽  
The University ◽  
Good Agreement

In hydraulic components, nonlinearities are responsible for critical behaviors that make it difficult to realize a reliable mathematical model for numerical simulation. With particular reference to hydraulic spool valves, the viscous friction coefficient between the sliding and the fixed body is an unknown parameter that is normally set a posteriori in order to obtain a good agreement with the experimental data. In this paper, two different methodologies to characterize experimentally the viscous friction coefficient in a hydraulic component with spool are presented. The two approaches are significantly different and are both based on experimental tests; they were developed in two distinct laboratories in different periods of time and applied to the same flow compensator of a pump displacement control. One of the procedures was carried out at the Fluid Power Research Laboratory of the Politecnico di Torino, while the other approach was developed at the University of Parma. Both the proposed methods reached similar outcomes; moreover, neither method requires the installation of a spool displacement transducer that can significantly affect the results.

The Frequency Response of Electrochemical Wall Shear Probes in Pulsatile Flow

1987 ◽  
Vol 109 (1) ◽  
pp. 60-64 ◽  
Author(s):  
L. Talbot ◽  
J. J. Steinert
Keyword(s):  
Mass Transfer ◽  
Frequency Response ◽  
Pulsatile Flow ◽  
Straight Tube ◽  
Asymptotic Results ◽  
Frequency Dependent ◽  
Shear Rates ◽  
Pulsatile Flows ◽  
Wall Shear ◽  
Good Agreement

The frequency response of surface-mounted electrochemical mass transfer probes used to deduce wall shear rates has been investigated experimentally for the case of fully developed laminar pulsatile flow in a straight tube. Generally good agreement is found with the asymptotic results obtained by Lighthill’s methods. The significance of the results with regard to the investigation of models of pulsatile flows of physiological interest is discussed. It is concluded that the frequency-dependent phase and amplitude corrections required to obtain accurate wall shear measurements are of such magnitudes as to render impractical the use of electrochemical probes to determine wall shear rates in these flows.

Frequency-dependent seismic analysis: Data processing, modeling, and interpretation

2019 ◽  
Vol 38 (7) ◽  
pp. 556-557
Author(s):  
Yi Shen ◽  
Kui Bao ◽  
Doug Foster ◽  
Dhananjay Kumar ◽  
Kris Innanen ◽  
...  
Keyword(s):  
Model Building ◽  
Seismic Analysis ◽  
Rock Physics ◽  
Analysis Data ◽  
Seismic Interpretation ◽  
Seismic Attenuation ◽  
Frequency Dependent ◽  
University Of Texas ◽  
Q Model ◽  
Physics Modeling

A one-day postconvention workshop held during the 2018 SEG Annual Meeting in Anaheim, California, focused on seismic attenuation model building and compensation through imaging in the morning and on frequency-dependent seismic interpretation and rock physics in the afternoon. The workshop was organized by Dhananjay Kumar (BP), Yi Shen (Shell), Kui Bao (Shell), Mark Chapman (University of Edinburgh), Doug Foster (The University of Texas at Austin), Wenyi Hu (Advanced Geophysical Tech Inc.), and Tieyuan Zhu (Pennsylvania State University). The main topics discussed were: attenuation and Q model building using seismic, vertical seismic profiling, well-log and core data, seismic attenuation compensation, rock-physics modeling, seismic modeling, and frequency-dependent seismic interpretation.

Attenuation study of a clay-rich dense zone in fractured carbonate reservoirs

Geophysics ◽  
2019 ◽  
Vol 84 (3) ◽  
pp. B205-B216
Author(s):  
Fateh Bouchaala ◽  
Mohammed Y. Ali ◽  
Jun Matsushima
Keyword(s):  
United Arab Emirates ◽  
Soft Clay ◽  
Seismic Profile ◽  
Seismic Attenuation ◽  
Carbonate Reservoirs ◽  
Intrinsic Attenuation ◽  
Flow Mechanisms ◽  
Order Of Magnitude ◽  
Attenuation Mechanism ◽  
Dense Zone

Seismic attenuation in clay-rich dense zones remains unknown, despite the importance of such zones in hydrocarbon reservoirs, where they delimit the reservoir zones and isolate them from nearby aquifers. We have determined that a dense zone separating two carbonate reservoirs of an onshore oilfield in Abu Dhabi, United Arab Emirates, exhibits the highest intrinsic attenuation even though the zone contains no hydrocarbons. The frictional movement due to the elastic contrast between the hard carbonates and soft clay is most likely the dominant mechanism in the dense zone. The compressional sonic and vertical seismic profile (VSP) attenuation are on the same order of magnitude and are both maximum in the dense zone. Therefore, it is possible that the same attenuation mechanism in this zone exists at low and high frequencies; whereas the intrinsic attenuation mechanism in the reservoir zones, which are more permeable and porous than the dense zone, can be explained by the coexistence of global and squirt-flow mechanisms. Moreover, sonic attenuation exhibits higher magnitudes than VSP attenuation in these zones. This is due to the fact that the squirt-flow mechanism, which can take place between pores and fractures, is more important at sonic frequencies. The scattering mechanism is also important in the reservoir zones; this is due to the high heterogeneity and the presence of fractures in these zones.

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