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    A transient fully coupled thermo-poroelastic finite element analysis of wellbore stability

    , Article Arabian Journal of Geosciences ; Volume 8, Issue 6 , 2014 , Pages 3855-3865 ; ISSN: 18667511 Gomar, M ; Goodarznia, I ; Shadizadeh, S. R ; Sharif University of Technology
    Abstract
    Stress variations around wellbores and in the reservoirs are of much interest in subsequent drilling operations, future production, and petroleum reservoir development. Stress variations induced by in situ stresses, pore pressure, and temperature changes during drilling operations may lead to various modes of instabilities in forms of induced fractures and borehole breakouts. Previous studies of thermally induced stresses were primarily based on either assumptions of heat conduction through rock matrix or heat convection, in this case, without considering the effect of solid grain thermal conductivity. To analyze wellbore stability, in the present work, a thermo-poro-mechanical model that is... 

    A poroelastic finite element model to describe the time-dependent response of lumbar intervertebral disc

    , Article Journal of Medical Imaging and Health Informatics ; Volume 1, Issue 3 , 2011 , Pages 246-251 ; 21567018 (ISSN) Nikkhoo, M ; Haghpanahi, M ; Wang, J. L ; Parnianpour, M ; Sharif University of Technology
    2011
    Abstract
    Investigation of the relationship between different types of mechanical loading and the failure of the intervertebral disc requires a well-defined finite element model. The objective of this paper was to develop and validate a nonlinear axisymmetric poroelastic finite element model of intervertebral disc and show its capability for studying the time-dependent response. After presenting the poroelastic model of intervertebral disc, the results of prolonged (short-term and long-term creep tests) and cyclic loading were compared with in vivo and in vitro experimental data. The trends predicted by FE model agreed well with measured experimental data and showed its validity for dynamic analysis.... 

    Simulation of wellbore stability with thermo-hydro-chemo-mechanical coupling in troublesome formations: an example from Ahwaz oil field, SW Iran

    , Article Arabian Journal of Geosciences ; Volume 8, Issue 1 , 2015 , Pages 379-396 ; 18667511 (ISSN) Rafieepour, S ; Jalayeri, H ; Ghotbi, C ; Pishvaie, M. R ; Sharif University of Technology
    Abstract
    Wellbore stability is a main concern in drilling operation. Troublesome drilling issues are chemically active formations and/or high-pressure–high-temperature environments. These are mainly responsible for most of wellbore instabilities. Wellbore failure is mostly controlled by the interaction between active shales and drilling fluid in shale formations. The factors influencing this interaction consist of fluid pressure, temperature, composition of drilling fluid, and exposure time. In this paper, a non-linear fully coupled chemo-thermo-poroelasticity model is developed. At first, a fully implicit finite difference model is presented to analyze the problem, and then, it is verified through... 

    Evaluation of sample scale effect on geomechanical tests

    , Article Petroleum Research ; Volume 7, Issue 4 , 2022 , Pages 527-535 ; 20962495 (ISSN) Kashfi, M ; Shad, S ; Zivar, D ; Sharif University of Technology
    KeAi Publishing Communications Ltd  2022
    Abstract
    The size of the rock specimen affects the stress concentrates in the vicinity of the top/bottom of the rock specimen during the evaluation of the geomechanical parameters in the laboratory, which causes unreliable results. However, the appropriate size for geomechanical evaluation is not well understood yet because of limitations in the sampling and analysis. In this study, a series of numerical simulations using a finite element package was conducted to investigate the effect of sample aspect ratio, fluid saturation, and porosity, on the mechanical behavior of the rock under elastic and poroelastic conditions. In addition, two concepts, stress/strain homogeneity index (SHI) and... 

    Fully coupled analysis of interaction between the borehole and pre-existing fractures

    , Article International Journal of Rock Mechanics and Mining Sciences ; Volume 89 , 2016 , Pages 151-164 ; 13651609 (ISSN) Gomar, M ; Goodarznia, I ; Shadizadeh, S. R ; Sharif University of Technology
    Elsevier Ltd  2016
    Abstract
    The coupling of rock and thermal stresses along with fluid pressure are particularly important in fractured rock masses, since stress-induced changes in permeability can be large and irreversible under perturbations resulting from various natural and induced activities. A new method is presented to model fracture permeability changes during drilling in fractured rocks. The approach includes finite element method (FEM) for fully coupled thermo-poroelastic analysis of stress distribution around borehole and displacement discontinuity method (DDM) to model fracture deformation. Three cases of overbalanced, underbalanced, and balanced drilling fluid pressure conditions are employed. The... 

    Wellbore Stability Analysis in Multiple Wells

    , M.Sc. Thesis Sharif University of Technology Yasami, Sina (Author) ; Goodarznia, Iraj (Supervisor)
    Abstract
    In an oil field, there always have been several wells which are produced or injected for several years, parameters such as pore pressure, temperature and stresses have been altered due to these production and injection wells. Having knowledge about the changes in mentioned parameters, new wellbores will confronts instability during drilling in high depth and sensitive layers. This thesis deals with the wellbore instability of sandstone formation with special focus on the effects of stresses and pore pressure changes caused by production and/or injection wells in the vicinity of the area that the new well would be drilled, to begin with the general assumptions and input parameters used in the... 

    An axisymmetric poroelastic model for description of the short-term and long-term creep behavior of L4-L5 intervertebral disc

    , Article 2011 1st Middle East Conference on Biomedical Engineering, MECBME 2011, Sharjah, 21 February 2011 through 24 February 2011 ; 2011 , Pages 308-311 ; 9781424470006 (ISBN) Nikkhoo, M ; Haghpanahi, M ; Parnianpour, M ; Wang, J. L ; Sharif University of Technology
    2011
    Abstract
    Understanding the relationship between different kinds of mechanical loading and the failure of the intervertebral disc is difficult to study in vivo and in vitro. Through finite element studies some of these issues may be overcome enabling more detailed assessment of the biomechanical behavior of the intervertebral disc. The objective of this paper is to develop a nonlinear axisymmetric poroelastic finite element model of intervertebral disc and show its capability for studying the time-dependent response of disc. After comparison of the response of different models in quasi-static analysis, the poroelastic model of intervertebral disc is presented and the results of a short-term and... 

    SVD analysis of dynamic properties for fatigue loaded intervertebral disc

    , Article 2011 1st Middle East Conference on Biomedical Engineering, MECBME 2011, 21 February 2011 through 24 February 2011, Sharjah ; 2011 , Pages 32-36 ; 9781424470006 (ISBN) Rozana, F ; Malik, A. S ; Wang, J. L ; Parnianpour, M ; Sharif University of Technology
    2011
    Abstract
    This paper uses singular value decomposition (SVD) for studying the dynamic properties of fatigue-loaded intervertebral disc. Previously, this problem had been addressed using mathematical models of using mass, spring and damper or based on poroelastic theory. This paper utilizes the signal processing approach and attempts to describe SVD based feature that can be an indicator for change in behavioral performance of the intervertebral disc warning the occurrence of temporary or permanent change in the structure or abnormality in behavior. The results are encouraging; however, further validation is required with more data  

    Transient thermo-poroelastic analysis of drilling-induced mechanical damage in nonfractured rocks

    , Article Arabian Journal of Geosciences ; Volume 8, Issue 12 , 2015 , Pages 10803-10818 ; 18667511 (ISSN) Gomar, M ; Goodarznia, I ; Shadizadeh, S. R ; Sharif University of Technology
    Springer Verlag  2015
    Abstract
    Permeability variations in reservoirs and around boreholes are of great interest in petroleum engineering due to the fact that they can significantly affect reserve estimates, reservoir development, well production or injection rate, and the likely success of remedial actions of near-wellbore damage. A fully coupled transient thermo-poroelastic concept with and without rock mechanical damage models is employed to evaluate stress distribution and permeability variation around the boreholes and breakouts. The anisotropy concept is applied to permeability, rock modulus, and uniaxial compressive strength using Weibull distribution. The Mogi–Coulomb failure criterion is employed to model breakout... 

    Energy absorption of the strengthened viscoelastic multi-curved composite panel under friction force

    , Article Archives of Civil and Mechanical Engineering ; Volume 21, Issue 4 , 2021 ; 16449665 (ISSN) Shao, Y ; Zhao, Y ; Gao, J ; Habibi, M ; Sharif University of Technology
    Springer Science and Business Media Deutschland GmbH  2021
    Abstract
    This study investigated FG carbon nanotubes filled composites, which are promising metamaterials that can be useful in the energy absorption field. This structure can absorb energy through elastic deformation. For this issue, absorbed energy and dynamic stability analysis of the FG-CNTRC curved panel surrounded by a non-polynomial viscoelastic substrate using three-dimensional poroelasticity theory is investigated. For stability of the structure after vibrating, the viscoelastic substrate as the non-polynomial viscoelastic model is presented. The curved panel comprises multilayer carbon nanotubes (CNT) which are uniformly distributed in all layers of facing sheets; however, the system’s... 

    Material property identification of artificial degenerated intervertebral disc models - comparison of inverse poroelastic finite element analysis with biphasic closed form solution

    , Article Journal of Mechanics ; Volume 29, Issue 4 , 2013 , Pages 589-597 ; 17277191 (ISSN) Nikkhoo, M ; Hsu, Y. C ; Haghpanahi, M ; Parnianpour, M ; Wang, J. L ; Sharif University of Technology
    2013
    Abstract
    ABSTRACT Disc rheological parameters regulate the mechanical and biological function of intervertebral disc. The knowledge of effects of degeneration on disc rheology can be beneficial for the design of new disc implants or therapy. We developed two material property identification protocols, i.e., inverse poroelas-tic finite element analysis, and biphasic closed form solution. These protocols were used to find the material properties of intact, moderate and severe degenerated porcine discs. Comparing these two computational protocols for intact and artificial degenerated discs showed they are valid in defining bi-phasic/poroelastic properties. We found that enzymatic agent disrupts the... 

    Coupled thermo-poroelastic analysis of drilling induced mechanical damage in fractured rocks

    , Article Journal of Petroleum Science and Engineering ; Volume 146 , 2016 , Pages 601-616 ; 09204105 (ISSN) Gomar, M ; Goodarznia, I ; Shadizadeh, S. R ; Sharif University of Technology
    Elsevier  2016
    Abstract
    The wellbore represents one of the most crucial components in the hydrocarbon and geothermal reservoir system, as it is the sole conduit to the reservoir for fluid production or injection. Therefore, predicting and controlling of the permeability variations close to the wellbore has been one of the most challenging issues in geothermal and petroleum reservoir systems. A new method is presented to model fracture permeability changes during drilling in fractured rocks. The approach includes finite element method (FEM) for fully coupled thermo-poroelastic analysis of stress distribution around borehole and displacement discontinuity method (DDM) to model fracture deformation. Four models of... 

    Mechanical and thermal stresses in FGPPM hollow cylinder due to radially symmetric loads

    , Article Journal of Pressure Vessel Technology, Transactions of the ASME ; Volume 138, Issue 1 , 2016 ; 00949930 (ISSN) Jabbari, M ; Meshkini, M ; Eslami, M. R ; Sharif University of Technology
    Abstract
    In this paper, the general solution of steady-state 1D radially symmetric mechanical and thermal stresses and electrical and mechanical displacements for a hollow thick cylinder made of fluid-saturated functionally graded poro piezoelectric materials (FGPPMs) is developed. The general form of thermal and mechanical boundary conditions is considered on the inside and outside surfaces. A direct method is used to solve the heat conduction equation and nonhomogenous system of partial differential Navier equations, using complex Fourier series and power law functions method. The material properties, except the Poisson ratio, are assumed to depend on the radial variable r and they are expressed as... 

    Bending analysis of FG-GPLRC axisymmetric circular/annular sector plates by considering elastic foundation and horizontal friction force using 3D-poroelasticity theory

    , Article Composite Structures ; Volume 276 , 2021 ; 02638223 (ISSN) Huo, J ; Zhang, G ; Ghabussi, A ; Habibi, M ; Sharif University of Technology
    Elsevier Ltd  2021
    Abstract
    Composite structures encounter different types of imperfections and defects during the installation, working environment, and fabrication process. In the present research, a 3D-poroflexibility theory has been presented to study the bending responses of the functionally graded graphene nanoplatelets reinforced composite (FG-GPLRC) axisymmetric circular/annular sector plates on the elastic substrate. For modeling elastic substrate, horizontal friction force and the elastic foundation with five elastic parameters have been formulated. For obtaining the exact displacement and stress/strain responses of the current structure, a discrete singular convolution integration method (DSC-IM) has been... 

    A meta-model analysis of a finite element simulation for defining poroelastic properties of intervertebral discs

    , Article Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine ; Volume 227, Issue 6 , 2013 , Pages 672-682 ; 09544119 (ISSN) Nikkhoo, M ; Hsu, Y. C ; Haghpanahi, M ; Parnianpour, M ; Wang, J. L ; Sharif University of Technology
    2013
    Abstract
    Finite element analysis is an effective tool to evaluate the material properties of living tissue. For an interactive optimization procedure, the finite element analysis usually needs many simulations to reach a reasonable solution. The metamodel analysis of finite element simulation can be used to reduce the computation of a structure with complex geometry or a material with composite constitutive equations. The intervertebral disc is a complex, heterogeneous, and hydrated porous structure. A poroelastic finite element model can be used to observe the fluid transferring, pressure deviation, and other properties within the disc. Defining reasonable poroelastic material properties of the... 

    A regenerative approach towards recovering the mechanical properties of degenerated intervertebral discs: Genipin and platelet-rich plasma therapies

    , Article Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine ; Volume 231, Issue 2 , 2017 , Pages 127-137 ; 09544119 (ISSN) Nikkhoo, M ; Wang, J. L ; Abdollahi, M ; Hsu, Y. C ; Parnianpour, M ; Khalaf, K ; Sharif University of Technology
    SAGE Publications Ltd  2017
    Abstract
    Degenerative disc disease, associated with discrete structural changes in the peripheral annulus and vertebral endplate, is one of the most common pathological triggers of acute and chronic low back pain, significantly depreciating an individual's quality of life and instigating huge socioeconomic costs. Novel emerging therapeutic techniques are hence of great interest to both research and clinical communities alike. Exogenous crosslinking, such as Genipin, and platelet-rich plasma therapies have been recently demonstrated encouraging results for the repair and regeneration of degenerated discs, but there remains a knowledge gap regarding the quantitative degree of effectiveness and... 

    A discretized analytical solution for fully coupled non-linear simulation of heat and mass transfer in poroelastic unsaturated media

    , Article International Journal for Numerical and Analytical Methods in Geomechanics ; Volume 33, Issue 13 , 2009 , Pages 1589-1611 ; 03639061 (ISSN) Arfaei Malekzadeh, F ; Pak, A ; Sharif University of Technology
    2009
    Abstract
    Mathematical simulation of non-isothermal multiphase flow in deformable unsaturated porous media is a complicated issue because of the need to employ multiple partial differential equations, the need to take into account mass and energy transfer between phases and because of the non-linear nature of the governing partial differential equations. In this paper, an analytical solution for analyzing a fully coupled problem is presented for the one-dimensional case where the coefficients of the system of equations are assumed to be constant for the entire domain. A major issue is the non-linearity of the governing equations, which is not considered in the analytical solution. In order to... 

    Numerical Evaluation of the Influence of Hydro-Mechanical Factors on the Conventional Methods of Hydraulic Fracture Analysis in Oil Reservoirs

    , M.Sc. Thesis Sharif University of Technology Saligheh Doust, Mostafa (Author) ; Pak, Ali (Supervisor)
    Abstract
    The exploitation of oil and gas has been changed dramatically since the advent of hydraulic fracturing. Hydraulic fracture is one of the enhanced oil recovery methods in which high-pressure injecting fluid is pumped into the well to overcome the lowest in-situ stress and rock resistance to create cracks in the deep-rock formations. It is estimated that the benefits of the mentioned method lead to a net economic profit of $48 billion per year in the world’s oil and gas industry.While there are various analytical models for predicting hydraulic fracture characteristics, KGD and PKN are amongst the most popular Models. The conditions of plane strain in two-dimensional space are taken into... 

    Prediction of Hydraulic Fracturing Technology in Naturally Fractured Rocks, by Considering Immiscible Two-phase Flow

    , Ph.D. Dissertation Sharif University of Technology Ranjbaran, Mohammad (Author) ; Taghikhani, Vahid (Supervisor) ; Ayatollahi, Shahab (Supervisor) ; Shad, Saeed (Supervisor) ; Ranjbaran, Abdolrasul ($item.subfieldsMap.e)
    Abstract
    To have a deeper understanding of Hydraulic fracturing operation, in this study four important parts in this field was developed and simulated. In the first part, continuity and momentum equations for a single phase flow in a propagating penny-shaped fracture inside an impermeable matrix was revisited based on a fixed coordinate system. Its correctness was validated against experimental data and its features were compared with the well-known lubrication theory in analytical form. The new derived continuity equation caused the fracture tip to have a positive and finite pressure while, the conventional model predicted negative infinity for that. In the second part, Finite Volume method was... 

    Analysis of different material theories used in a FE model of a lumbar segment motion

    , Article Acta of Bioengineering and Biomechanics ; Volume 15, Issue 2 , 2013 , Pages 33-41 ; 1509409X (ISSN) Gohari, E ; Nikkhoo, M ; Haghpanahi, M ; Parnianpour, M ; Sharif University of Technology
    2013
    Abstract
    In this study, a nonlinear poroelastic model of intervertebral disc as an infrastructure was developed. Moreover, a new element was defined consisting a disc (Viscoelastic Euler Beam Element) and a vertebra (Rigid Link) as a unit element. Using the new element, three different viscoelastic finite element models were prepared for lumbar motion segment (L4/L5). Prolonged loading (short-term and long-term creep) and cyclic loading were applied to the models and the results were compared with results of in vivo tests. Simplification of the models by using the new element leads to reduction of the runtime of the models in dynamic analyses to few minutes without losing the accuracy in the results