Poroelasticity: Efficient modeling of strongly coupled, slow deformation processes in a multilayered half‐space

Geophysics ◽  
2003 ◽  
Vol 68 (2) ◽  
pp. 705-717 ◽  
Author(s):  
Rongjiang Wang ◽  
Hans‐Joachim Kümpel
Keyword(s):  
Half Space ◽  
Numerical Scheme ◽  
Surface Deformation ◽  
Fluid Pressure ◽  
Mirror Image ◽  
Excess Pore Pressure ◽  
Near Surface ◽  
Strongly Coupled ◽  
Image Technique ◽  
Subsurface Reservoir

We present a fast, powerful numerical scheme to compute poroelastic solutions for excess pore pressure and displacements in a multilayered half‐space. The solutions are based on the mirror‐image technique and use an extension of Haskell's propagator method. They can be applied to assess in‐situ formation parameters from the surface deformation field when fluids are injected into or extracted from a subsurface reservoir, or they can be used to simulate changes in pore‐fluid pressure resulting from matrix displacements induced by an earthquake. The performance of the numerical scheme is tested through comparison with observations of the surface deformation as recorded by tiltmeters in the vicinity of an iteratively pumped well. Modeling of near‐surface tilt data around a productive well is useful in constraining hydraulic diffusivity in the layered subsurface.

scholarly journals Fault source investigation of the 6 December 2016 MwMw 6.5 Pidie Jaya, Indonesia, earthquake based on GPS and its implications of the geological survey result

2020 ◽  
Vol 14 (4) ◽  
pp. 405-412
Author(s):  
Endra Gunawan ◽  
Takuya Nishimura ◽  
Susilo Susilo ◽  
Sri Widiyantoro ◽  
Nanang T. Puspito ◽  
...  
Keyword(s):  
Surface Deformation ◽  
Source Parameters ◽  
Secondary Effects ◽  
Near Surface ◽  
Morphological Attributes ◽  
Ground Shaking ◽  
The North ◽  
Coulomb Failure ◽  
North And South ◽  
Fault Source

AbstractOn 6 December 2016 at 22:03 UTC, a devastating magnitude 6-class strike-slip earthquake occurred along an unidentified and unmapped fault in Pidie Jaya, northern Sumatra. We analysed the possible fault using continuous Global Positioning System (GPS) observation available in the region. In our investigation, we searched for the fault source parameters of the north- and south-dipping left-lateral faults and the west- and east-dipping right-lateral faults. We identified that the fault responsible for the earthquake was located offshore, with a southwest-northeast direction. We also computed the Coulomb failure stress and compared the result with the distribution of the aftershocks. In this study, we demonstrated that the result of the geological field survey conducted soon after the mainshock was attributed to the secondary effects of ground shaking and near-surface deformation, and not surface faulting. The newly identified offshore fault proposed by this study calls for further investigation of the corresponding submarine morphological attributes in this particular region.

scholarly journals Elucidating the Onset of Plasticity in Sliding Contacts Using Differential Computational Orientation Tomography

2021 ◽  
Vol 69 (3) ◽  
Author(s):  
S. J. Eder ◽  
P. G. Grützmacher ◽  
M. Rodríguez Ripoll ◽  
J. F. Belak
Keyword(s):  
Grain Boundary ◽  
Large Scale ◽  
Surface Deformation ◽  
Boundary Migration ◽  
Material Design ◽  
Lattice Rotation ◽  
Time Resolved ◽  
Near Surface ◽  
Color Saturation ◽  
Dynamics Simulations

Abstract Depending on the mechanical and thermal energy introduced to a dry sliding interface, the near-surface regions of the mated bodies may undergo plastic deformation. In this work, we use large-scale molecular dynamics simulations to generate “differential computational orientation tomographs” (dCOT) and thus highlight changes to the microstructure near tribological FCC alloy surfaces, allowing us to detect subtle differences in lattice orientation and small distances in grain boundary migration. The analysis approach compares computationally generated orientation tomographs with their undeformed counterparts via a simple image analysis filter. We use our visualization method to discuss the acting microstructural mechanisms in a load- and time-resolved fashion, focusing on sliding conditions that lead to twinning, partial lattice rotation, and grain boundary-dominated processes. Extracting and laterally averaging the color saturation value of the generated tomographs allows us to produce quantitative time- and depth-resolved maps that give a good overview of the progress and severity of near-surface deformation. Corresponding maps of the lateral standard deviation in the color saturation show evidence of homogenization processes occurring in the tribologically loaded microstructure, frequently leading to the formation of a well-defined separation between deformed and undeformed regions. When integrated into a computational materials engineering framework, our approach could help optimize material design for tribological and other deformation problems. Graphic Abstract .

Inversion of slingram electromagnetic induction data using a Born approximation

Geophysics ◽  
2013 ◽  
Vol 78 (4) ◽  
pp. E201-E212 ◽  
Author(s):  
Jochen Kamm ◽  
Michael Becken ◽  
Laust B. Pedersen
Keyword(s):  
Half Space ◽  
Born Approximation ◽  
High Efficiency ◽  
Three Dimensions ◽  
Background Model ◽  
Desktop Computer ◽  
Near Surface ◽  
Homogeneous Half Space ◽  
Integral Equation Formulation ◽  
Forward Operator

We present an efficient approximate inversion scheme for near-surface loop-loop EM induction data (slingram) that can be applied to obtain 2D or 3D models on a normal desktop computer. Our approach is derived from a volume integral equation formulation with an arbitrarily conductive homogeneous half-space as a background model. The measurements are not required to fulfill the low induction number condition (low frequency and conductivity). The high efficiency of the method is achieved by invoking the Born approximation around a half-space background. The Born approximation renders the forward operator linear. The choice of a homogeneous half-space yields closed form expressions for the required electromagnetic normal fields. It also yields a translationally invariant forward operator, i.e., a highly redundant Jacobian. In connection with the application of a matrix-free conjugate gradient method, this allows for very low memory requirements during the inversion, even in three dimensions. As a consequence of the Born approximation, strong conductive deviations from the background model are underestimated. Highly resistive anomalies are in principle overestimated, but at the same time difficult to resolve with induction methods. In the case of extreme contrasts, our forward model may fail in simultaneously explaining all the data collected. We applied the method to EM34 data from a profile that has been extensively studied with other electromagnetic methods and compare the results. Then, we invert three conductivity maps from the same area in a 3D inversion.

scholarly journals Fluid pressure arrival-time tomography: Estimation and assessment in the presence of inequality constraints with an application to production at the Krechba field, Algeria

Geophysics ◽  
2010 ◽  
Vol 75 (6) ◽  
pp. O39-O55 ◽  
Author(s):  
Alessio Rucci ◽  
D. W. Vasco ◽  
Fabrizio Novali
Keyword(s):  
Surface Deformation ◽  
Transient Flow ◽  
Fluid Pressure ◽  
Inequality Constraints ◽  
Gas Production ◽  
Gas Field ◽  
Peak Displacement ◽  
Geomechanical Properties ◽  
Fluid Production ◽  
Using Data

Deformation in the overburden proves useful in deducing spatial and temporal changes in the volume of a producing reservoir. Based on these changes, we have estimated diffusive traveltimes associated with the transient flow due to production, and then, as the solution of a linear inverse problem, the effective permeability of the reservoir. An advantage of the approach based on traveltimes, as opposed to one based on the amplitude of surface deformation, is that it is much less sensitive to the exact geomechanical properties of the reservoir and overburden. Inequalities constrain the inversion, under the assumption that the fluid production only results in pore volume decreases within the reservoir. The formulation has been applied to satellite-based estimates of deformation in the material overlying a thin gas production zone at the Krechba field in Algeria. The peak displacement after three years of gas production is found to be approximately [Formula: see text], overlying the eastern margin of the anticlinal structure defining the gas field. Using data from 15 irregularly spaced images of range change, we have calculated the diffusive traveltimes associated with the startup of a gas production well. The inequality constraints were incorporated into the estimates of model parameter resolution and covariance, improving the resolution by roughly 30% to 40%.

Residual Stress in Bone: A Parametric Study

2008 ◽  
Author(s):  
A. Hizal ◽  
B. Sadasivam ◽  
D. Arola
Keyword(s):  
Residual Stress ◽  
Particle Size ◽  
Residual Stresses ◽  
Material Removal ◽  
Surface Deformation ◽  
Radius Of Curvature ◽  
Near Surface ◽  
Size And Shape ◽  
Air Jet ◽  
Particle Size And Shape

A preliminary study was conducted to evaluate the parametric dependence of the residual stress distributions in bone that result from an abrasive air-jet surface treatment. Specifically, the influence of particle size and shape used in the treatment on the residual stress, propensity of embedding particles and material removal were studied. Rectangular beams of cortical bone were prepared from bovine femurs and treated with aluminum oxide and glass particles with different treatment angles. Residual stresses within the bone were quantified in terms of the radius of curvature of the bone specimens measured before and after the treatments, as well as a function of time to quantify decay in the stress. The sub-surface distribution was also examined using the layer removal technique. Results showed that the particle size and shape could be used to control the amount of material removal and the magnitude of residual stress within the treated surfaces. An increase in size of the glass particles resulted in an increase in the residual stress and a decrease in material removed during the treatment. The magnitude of residual stress ranged from 22 MPa to nearly 44 MPa through modulation of the particle qualities (size and shape). A microscopic examination of the treated surfaces suggests that the residual stresses resulted primarily from near-surface deformation.

scholarly journals Thermodynamical Extension of a Symplectic Numerical Scheme with Half Space and Time Shifts Demonstrated on Rheological Waves in Solids

Entropy ◽  
2020 ◽  
Vol 22 (2) ◽  
pp. 155 ◽  
Author(s):  
Tamás Fülöp ◽  
Róbert Kovács ◽  
Mátyás Szücs ◽  
Mohammad Fawaier
Keyword(s):  
Finite Element ◽  
Wave Propagation ◽  
Dispersion Relation ◽  
Half Space ◽  
Numerical Stability ◽  
Numerical Scheme ◽  
Nonlinear Dispersion ◽  
Finite Element Software ◽  
Space And Time ◽  
Nonlinear Dispersion Relation

On the example of the Poynting–Thomson–Zener rheological model for solids, which exhibits both dissipation and wave propagation, with nonlinear dispersion relation, we introduce and investigate a finite difference numerical scheme. Our goal is to demonstrate its properties and to ease the computations in later applications for continuum thermodynamical problems. The key element is the positioning of the discretized quantities with shifts by half space and time steps with respect to each other. The arrangement is chosen according to the spacetime properties of the quantities and of the equations governing them. Numerical stability, dissipative error, and dispersive error are analyzed in detail. With the best settings found, the scheme is capable of making precise and fast predictions. Finally, the proposed scheme is compared to a commercial finite element software, COMSOL, which demonstrates essential differences even on the simplest—elastic—level of modeling.

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