scholarly journals IMPACT OF FRACTURED-POROUS MEDIA TRANSPORT PROPERTIES CHANGE IN SEISMIC WAVEFIELDS

2019 ◽  
Vol 2 (2) ◽  
pp. 248-253
Author(s):  
Mikhail Novikov ◽  
Vadim Lisitsa ◽  
Tatiana Khachkova
Keyword(s):  
Co2 Sequestration ◽  
Velocity Dispersion ◽  
Ct Scans ◽  
Filling Material ◽  
Wave Fields ◽  
Poroelastic Material ◽  
Porous Reservoir ◽  
Saturated Media ◽  
Wave Induced ◽  
Dispersion And Attenuation

In this paper we research the response of carbonates dissolution when interacting with carbon dioxide in the seismic wave fields in a fractured-porous reservoir. We numerically estimate the change of limestone physical properties due to CO2 sequestration based on the analysis of samples CT-scans. Obtained estimations is then used to model a poroelastic material, which we use as fracture-filling material in statistically generated fractured porous fluid-saturated media models. A numerical modeling of wave propagation is performed to estimate a velocity dispersion and attenuation caused by a wave-induced fluid flow.

scholarly journals NUMERICAL ALGORITHM OF SEISMIC ATTENUATION ESTIMATION IN ANISOTROPIC FRACTURED POROUS FLUID-SATURATED MEDIA

2021 ◽  
Vol 2 (2) ◽  
pp. 186-195
Author(s):  
Mikhail A. Novikov ◽  
Vadim V. Lisitsa
Keyword(s):  
Fluid Flow ◽  
Seismic Wave ◽  
Numerical Algorithm ◽  
Wave Attenuation ◽  
Seismic Attenuation ◽  
Staggered Grid ◽  
Filling Material ◽  
Seismic Wave Attenuation ◽  
Saturated Media ◽  
Wave Induced

In our work we investigate the effect of transport and elastic properties anisotropy on seismic attenuation due to fracture-to-fracture wave-induced fluid flow using numerical algorithm of estimation of seismic wave attenuation in anisotropic fractured porous fluid-saturated media. Algorithm is based on numerical solution of anisotropic Biot equations using finite-difference scheme on staggered grid. We perform a set of numerical experiments to model wave propagation in fractured media with anisotropic fractured-filling material providing wave-induced fluid flow within interconnected fractures. Recorded signals are used for numerical estimation of inverse quality factor. Results demonstrate the effect of fracture-filling material anisotropy on seismic wave attenuation.

Wave-induced mean flows in rotating shallow water with uniform potential vorticity

2018 ◽  
Vol 839 ◽  
pp. 408-429 ◽  
Author(s):  
Jim Thomas ◽  
Oliver Bühler ◽  
K. Shafer Smith
Keyword(s):  
Shallow Water ◽  
Potential Vorticity ◽  
Rotation Rate ◽  
Standing Waves ◽  
Leading Order ◽  
Mean Flow ◽  
Wave Fields ◽  
The Mean ◽  
Rotating Shallow Water ◽  
Wave Induced

Theoretical and numerical computations of the wave-induced mean flow in rotating shallow water with uniform potential vorticity are presented, with an eye towards applications in small-scale oceanography where potential-vorticity anomalies are often weak compared to the waves. The asymptotic computations are based on small-amplitude expansions and time averaging over the fast wave scale to define the mean flow. Importantly, we do not assume that the mean flow is balanced, i.e. we compute the full mean-flow response at leading order. Particular attention is paid to the concept of modified diagnostic relations, which link the leading-order Lagrangian-mean velocity field to certain wave properties known from the linear solution. Both steady and unsteady wave fields are considered, with specific examples that include propagating wavepackets and monochromatic standing waves. Very good agreement between the theoretical predictions and direct numerical simulations of the nonlinear system is demonstrated. In particular, we extend previous studies by considering the impact of unsteady wave fields on the mean flow, and by considering the total kinetic energy of the mean flow as a function of the rotation rate. Notably, monochromatic standing waves provide an explicit counterexample to the often observed tendency of the mean flow to decrease monotonically with the background rotation rate.

Impact of fluid saturation on the reflection coefficient of a poroelastic layer

Geophysics ◽  
2011 ◽  
Vol 76 (2) ◽  
pp. N1-N12 ◽  
Author(s):  
Beatriz Quintal ◽  
Stefan M. Schmalholz ◽  
Yuri Y. Podladchikov
Keyword(s):  
Fluid Flow ◽  
Reflection Coefficient ◽  
Analytical Solution ◽  
Quality Factor ◽  
Velocity Dispersion ◽  
Normal Incidence ◽  
Sand Layer ◽  
Partially Saturated ◽  
Fluid Saturation ◽  
Wave Induced

The impact of changes in saturation on the frequency-dependent reflection coefficient of a partially saturated layer was studied. Seismic attenuation and velocity dispersion in partially saturated (i.e., patchy saturated) poroelastic media were accounted for by using the analytical solution of the 1D White’s model for wave-induced fluid flow. White’s solution was applied in combination with an analytical solution for the normal-incidence reflection coefficient of an attenuating layer embedded in an elastic or attenuating background medium to investigate the effects of attenuation, velocity dispersion, and tuning on the reflection coefficient. Approximations for the frequency-dependent quality factor, its minimum value, and the frequency at which the minimum value of the quality factor occurs were derived. The approximations are valid for any two alternating sets of petrophysical parameters. An approximation for the normal-incidence reflection coefficient of an attenuating thin (compared to the wavelength) layer was also derived. This approximation gives insight into the influence of contrasts in acoustic impedance and/or attenuation on the reflectivity of a thin layer. Laboratory data for reflections from a water-saturated sand layer and from a dry sand layer were further fit with petrophysical parameters for unconsolidated sand partially saturated with water and air. The results showed that wave-induced fluid flow can explain low-frequency reflection anomalies, which are related to fluid saturation and can be observed in seismic field data. The results further indicate that reflection coefficients of partially saturated layers (e.g., hydrocarbon reservoirs) can vary significantly with frequency, especially at low seismic frequencies where partial saturation may often cause high attenuation.

scholarly journals Unified theory of global flow and squirt flow in cracked porous media

Geophysics ◽  
2009 ◽  
Vol 74 (2) ◽  
pp. WA65-WA76 ◽  
Author(s):  
Morten Jakobsen ◽  
Mark Chapman
Keyword(s):  
Porous Media ◽  
Velocity Dispersion ◽  
Solid Matrix ◽  
Global Flow ◽  
Local Pressure ◽  
Fluid Mass ◽  
T Matrix ◽  
Wave Induced ◽  
Cracked Porous Media ◽  
Single Set

Approximations for frequency-dependent and complex-valued effective stiffness tensors of cracked porous media (saturated with a single fluid) are developed on the basis of an inclusion-based model (the T-matrix approach to rock physics) and a unified treatment of the global-flow and squirt-flow mechanisms. Essentially, this study corrects an inconsistency or error related to fluid-mass conservation in an existing expression for the t-matrix (wave-induced deformation) of a communicating cavity, a cavity that is isolated with respect to stress propagation (through the solid matrix) but that can exchange fluid mass with other cavities because of global and/or local pressure gradients associated with passage of a long viscoelastic wave. An earlier demonstration of Gassmann consistency remains valid because the new theory of global flow and squirt flow (which also takes into account solid mechanical effects of stress interaction by us-ing products of communicating t-matrices associated with two-point correlation functions of ellipsoidal symmetry) only differs from an earlier version by a correction term that goes to zero in the low-frequency limit. If the unified model is applied to the special case of a model involving a single set of spheroidal cavities (having the same aspect ratio and orientation), the results become identical with those obtained using a special theory of global flow that predicts that at zero frequency the cavities will behave as though they are isolated with respect to wave-induced fluid flow (in accordance with Gassmann’s formulas) and that at high frequencies, they will behave as though they are dry. Our theory predicts that there will be a continuous transition from a global-flow-dominated system (characterized by a negative velocity dispersion) to a squirt-flow-dominated system (characterized by a positive velocity dispersion) if one begins with a single set of cavities and then introduces a distribution of shapes and/or orientations that gradually becomes wider (more realistic).

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