Pore Collapse in Weakly Cemented and Porous Rocks

1994 ◽  
Vol 116 (2) ◽  
pp. 97-103 ◽  
Author(s):  
M. Zaman ◽  
J.-C. Roegiers ◽  
A. Abdulraheem ◽  
M. Azeemuddin
Keyword(s):  
Experimental Data ◽  
Constitutive Model ◽  
Isotropic Hardening ◽  
High Porosity ◽  
Porous Rocks ◽  
Pore Collapse ◽  
Reservoir Rocks ◽  
Model Predictions ◽  
Elasto Plasticity ◽  
Collapse Behavior

Withdrawal of fluids from hydrocarbon reservoirs results in a decrease in pore pressure which in turn leads to an increase in effective stress on rock matrix. Such a situation may lead to the occurrence of pore collapse in reservoirs having weakly cemented, porous rocks. It is considered to be a potential problem in several producing reservoirs. Numerical simulation of a compacting reservoir due to pore collapse requires an appropriate constitutive model. Consequently, a constitutive model based on the concept of elasto-plasticity using isotropic hardening is developed to predict pre and post-pore collapse behavior of reservoir rocks. An experimental study is carried out on a high-porosity rock susceptible to pore collapse for different stress paths. The developed constitutive model is tested with respect to two different materials exhibiting such behavior. Parameters for the model are evaluated based on the experimental results, highlighting the procedure involved. Further, the data is used to demonstrate the strengths and the weaknesses of the constitutive model. Experimental data for the second material is obtained from literature. Satisfactory agreement is achieved between experimental data and model predictions.

Cyclic Viscoplastic Constitutive Equations, Part II: Stored Energy—Comparison Between Models and Experiments

1993 ◽  
Vol 60 (4) ◽  
pp. 822-828 ◽  
Author(s):  
J.-L. Chaboche
Keyword(s):  
Experimental Data ◽  
Constitutive Equations ◽  
Mechanical Response ◽  
Isotropic Hardening ◽  
Half Cycle ◽  
Stored Energy ◽  
Closed Form Solutions ◽  
Independent Form ◽  
Model Predictions ◽  
Present Part

The cyclic constitutive equations developed at ONERA have been incorporated into a general thermodynamic framework (Part I). In the present part, systematic comparisons are given between the model predictions and experimental data for both the mechanical response and the energy stored in the material. The models are specified in their rate—independent-form and closed-form solutions are obtained for tension-compression monotonic and cyclic conditions. By superposing one or two nonlinear kinematic rules and one isotropic hardening equation, the available experimental data are fairly well reproduced. In particular it is possible to describe the low values of stored energy, the decrease of the ratio of stored energy to total plastic work as a function of strain, and the partial release of stored energy at every half cycle of a cyclic loading.

Effect of Loading Path and Porosity on the Failure Mode of Porous Rocks

1992 ◽  
Vol 45 (8) ◽  
pp. 281-293 ◽  
Author(s):  
Teng-fong Wong ◽  
Hiram Szeto ◽  
Jiaxiang Zhang
Keyword(s):  
Acoustic Emission ◽  
Strain Hardening ◽  
Yield Locus ◽  
Loading Path ◽  
High Porosity ◽  
Porous Rocks ◽  
Stress Space ◽  
Pore Collapse ◽  
Clastic Rocks ◽  
Grain Crushing

Grain crushing and pore collapse are the dominant compaction mechanisms in high porosity clastic rocks. These micromechanical processes control the evolution of strain hardening during cataclastic flow, and they can also result in embrittlement of the rock. The mechanics of the transition from brittle fracture to homogeneous cataclastic flow for the Berea and Kayenta sandstones were investigated in the laboratory. The mechanical data show that the transition is sensitively dependent on the stress state as well as the porosity. In the stress space, the complete locus for brittle failure by shear localization can be determined by tests on normally consolidated and overconsolidated samples along different loading paths. Using porosity as the hardening parameter, the evolution of the inelastic yield locus with strain hardening can be mapped out in the stress space. This yield locus expands with decreasing porosity. Scanning electron microscope and acoustic emission measurements were used to elucidate the micromechanics. The onset of grain crushing and pore collapse was marked by a surge in acoustic emission activity. A Hertzian fracture mechanics model was formulated to analyze the roles of porosity, grain size and fracture toughness in controlling the onset of hydrostatic and shear-enhanced compaction. Stereological measurements of the microcrack density show that significant stress-induced anisotropy was induced by shear-enhanced compaction, with preferred orientations of the stress-induced microcracks subparallel to the maximum compression direction.

STUDY OF THE EFFECT OF CAPILLARY PRESSURE ON PERMEABILITY

Fractals ◽  
2007 ◽  
Vol 15 (01) ◽  
pp. 55-62 ◽  
Author(s):  
YANJUN LIU ◽  
BOMING YU ◽  
PENG XU ◽  
JINSUI WU
Keyword(s):  
Experimental Data ◽  
Capillary Pressure ◽  
Significant Influence ◽  
Present Model ◽  
Pressure Effect ◽  
High Porosity ◽  
Permeability Model ◽  
Model Predictions ◽  
Good Agreement ◽  
Low Porosity

A fractal permeability model which accounts for the capillary pressure is derived, and the permeability contribution from the capillary pressure is analyzed. The predicted permeability is compared with the available experimental data, and good agreement is found between the present model predictions and available experimental data. The results show that at low porosity (< 0.35), the capillary pressure has the significant influence on the total permeability, and the capillary pressure effect cannot be neglected. But at high porosity (> 0.35), the effect of capillary pressure on permeability is insignificant.

Predictions of MSMA Response Under Bi-Axial Mechanical Loading

2014 ◽  
Author(s):  
Jason L. Dikes ◽  
Heidi P. Feigenbaum ◽  
Constantin Ciocanel
Keyword(s):  
Magnetic Field ◽  
Experimental Data ◽  
Constitutive Model ◽  
Shape Memory ◽  
Mechanical Loading ◽  
Magnetic Shape Memory ◽  
Magnetic Shape Memory Alloys ◽  
Power Harvesting ◽  
Compressive Stresses ◽  
Model Predictions

Magnetic shape memory alloys (MSMAs) are materials commonly used for actuation, sensing, and/or power harvesting applications. To date, these applications have primarily been explored under a magnetic field and/or a compressive stress, with the stress and the field acting along directions perpendicular to each other. However, other applications may be envisioned, and existing applications may be optimized, with alternate load configurations. The alternate load configuration to be explored in this work is the application of bi-axial compressive stresses. This configuration could be used in actuation or power harvesting applications. A constitutive model, proposed by LaMaster et al. [1], is simplified and used to predict the response of the material under bi-axial compressive stresses. Model predictions are compared with experimental data from the literature.

scholarly journals Constitutive Modeling of the Densification Behavior in Open-Porous Cellular Solids

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2731
Author(s):  
Ameya Rege
Keyword(s):  
Constitutive Model ◽  
Cell Walls ◽  
Compressive Strain ◽  
Pore Collapse ◽  
Compressive Response ◽  
Linear Elastic ◽  
Nonlinear Springs ◽  
Different Types ◽  
Point Of Intersection ◽  
Good Agreement

The macroscopic mechanical behavior of open-porous cellular materials is dictated by the geometric and material properties of their microscopic cell walls. The overall compressive response of such materials is divided into three regimes, namely, the linear elastic, plateau and densification. In this paper, a constitutive model is presented, which captures not only the linear elastic regime and the subsequent pore-collapse, but is also shown to be capable of capturing the hardening upon the densification of the network. Here, the network is considered to be made up of idealized square-shaped cells, whose cell walls undergo bending and buckling under compression. Depending on the choice of damage criterion, viz. elastic buckling or irreversible bending, the cell walls collapse. These collapsed cells are then assumed to behave as nonlinear springs, acting as a foundation to the elastic network of active open cells. To this end, the network is decomposed into an active network and a collapsed one. The compressive strain at the onset of densification is then shown to be quantified by the point of intersection of the two network stress-strain curves. A parameter sensitivity analysis is presented to demonstrate the range of different material characteristics that the model is capable of capturing. The proposed constitutive model is further validated against two different types of nanoporous materials and shows good agreement.

A Cyclic Plasticity Modeling for Uniaxial and Multiaxial Ratcheting Simulation of Austenitic Steel

2012 ◽  
Author(s):  
Salim Meziani ◽  
Lynda Djimli
Keyword(s):  
Experimental Data ◽  
Stainless Steel ◽  
Constitutive Model ◽  
Data Base ◽  
Good Choice ◽  
Cyclic Plasticity ◽  
Strain History ◽  
Material Parameters ◽  
Plastic Shakedown

The first objective of this paper investigates the influence of the previous strain history on ratcheting of the 304 L stainless steel on ambient temperature. The identification is done using the Chaboche constitutive model. New tests were performed where different strain-controlled histories have been applied prior to ratcheting tests. It is demonstrated that under the same conditions, one can observe ratcheting, plastic shakedown or elasticity according to the prior strain-controlled history. The second objective points out the correlation between the experimental data base devoted to the identification of the material parameters and the quality of the predictions in cyclic plasticity. The results suggest that the choice of the tests should be closely linked to the capabilities of the model. In particular, the presence of non proportional strain-controlled tests in the data base may be not a good choice if the model itself is not able to represent explicitly such a character.

scholarly journals Multi-Scale Analyses and Modeling of Metallic Nano-Layers

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 450
Author(s):  
Zara Moleinia ◽  
David Bahr
Keyword(s):  
Experimental Data ◽  
Constitutive Model ◽  
Crystal Plasticity ◽  
Single Layer ◽  
Adaptive Boosting ◽  
Multi Scale ◽  
Nano Scale ◽  
Boosting Technique ◽  
Constitutive Parameters ◽  
Computational Processes

The current work centers on multi-scale approaches to simulate and predict metallic nano-layers’ thermomechanical responses in crystal plasticity large deformation finite element platforms. The study is divided into two major scales: nano- and homogenized levels where Cu/Nb nano-layers are designated as case studies. At the nano-scale, a size-dependent constitutive model based on entropic kinetics is developed. A deep-learning adaptive boosting technique named single layer calibration is established to acquire associated constitutive parameters through a single process applicable to a broad range of setups entirely different from those of the calibration. The model is validated through experimental data with solid agreement followed by the behavioral predictions of multiple cases regarding size, loading pattern, layer type, and geometrical combination effects for which the performances are discussed. At the homogenized scale, founded on statistical analyses of microcanonical ensembles, a homogenized crystal plasticity-based constitutive model is developed with the aim of expediting while retaining the accuracy of computational processes. Accordingly, effective constitutive functionals are realized where the associated constants are obtained via metaheuristic genetic algorithms. The model is favorably verified with nano-scale data while accelerating the computational processes by several orders of magnitude. Ultimately, a temperature-dependent homogenized constitutive model is developed where the effective constitutive functionals along with the associated constants are determined. The model is validated by experimental data with which multiple demonstrations of temperature effects are assessed and analyzed.

CH4 Direct Reduction of In-Flight Fe3O4 Concentrate Particles

2018 ◽  
Vol 14 (1) ◽  
Author(s):  
Bahador Abolpour ◽  
M. Mehdi Afsahi ◽  
Ataallah Soltani Goharrizi
Keyword(s):  
Experimental Data ◽  
Mathematical Model ◽  
Fine Particles ◽  
Direct Reduction ◽  
Constant Heat Flux ◽  
Constant Heat ◽  
Dynamic Motion ◽  
Magnetite Ore ◽  
Model Predictions ◽  
Kinetics Of

Abstract In this study, reduction of in-flight fine particles of magnetite ore concentrate by methane at a constant heat flux has been investigated both experimentally and numerically. A 3D turbulent mathematical model was developed to simulate the dynamic motion of these particles in a methane content reactor and experiments were conducted to evaluate the model. The kinetics of the reaction were obtained using an optimizing method as: [-Ln(1-X)]1/2.91 = 1.02 × 10−2dP−2.07CCH40.16exp(−1.78 × 105/RT)t. The model predictions were compared with the experimental data and the data had an excellent agreement.

scholarly journals A combined model for pseudo-rapidity distributions in Cu–Cu collisions at BNL-RHIC energies

2016 ◽  
Vol 25 (04) ◽  
pp. 1650025 ◽  
Author(s):  
Z. J. Jiang ◽  
J. Wang ◽  
Y. Huang
Keyword(s):  
Experimental Data ◽  
Proper Time ◽  
Charged Particles ◽  
Dense Matter ◽  
Rapidity Distribution ◽  
Experimental Measurements ◽  
Combined Model ◽  
Model Predictions ◽  
Phobos Collaboration ◽  
Rapidity Distributions

The charged particles produced in nucleus–nucleus collisions come from leading particles and those frozen out from the hot and dense matter created in collisions. The leading particles are conventionally supposed having Gaussian rapidity distributions normalized to the number of participants. The hot and dense matter is assumed to expand according to the unified hydrodynamics, a hydro model which unifies the features of Landau and Hwa–Bjorken model, and freeze out into charged particles from a time-like hypersurface with a proper time of [Formula: see text]. The rapidity distribution of this part of charged particles can be derived analytically. The combined contribution from both leading particles and unified hydrodynamics is then compared against the experimental data performed by BNL-RHIC-PHOBOS Collaboration in different centrality Cu–Cu collisions at [Formula: see text] and 62.4[Formula: see text]GeV, respectively. The model predictions are consistent with experimental measurements.

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