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Development of Directional Drilling Key Performance Indicators (KPIs) for Optimization Purposes
, M.Sc. Thesis Sharif University of Technology ; Jamshidi, Saeed (Supervisor) ; Fazaelizadeh, Mohammad (Co-Supervisor)
Abstract
In drilling operations, cost, time, and quality are the three factors to consider for evaluation. Drilling optimization means reducing project costs and completing them as quickly as possible while still meeting the standards. Due to the complexity and specificity of directional drilling and the increasing need for this type of drilling, optimizing the directional drilling operation is of great importance. Drilling rate of penetration and hydromechanical specific energy are considered as two main indicators of drilling performance in this thesis. In the first step, drilling rate of penetration is predicted using drilling data and machine learning algorithms and then single-objective and...
Numerical simulation of sanding using a coupled hydro-mechanical sand erosion model
, Article Journal of Rock Mechanics and Geotechnical Engineering ; Volume 12, Issue 4 , 2020 , Pages 811-820 ; Pak, A ; Sharif University of Technology
Chinese Academy of Sciences
2020
Abstract
Mechanical failure of materials adjacent to the production cavity and material disaggregation caused by fluid drag are considered as the most important parameters that affect sand production. In light of such factors, the coupling of two mechanisms-mechanical instability and hydrodynamic erosion-is indispensable in order to model this phenomenon successfully. This paper examines the applicability of a coupled hydro-mechanical erosion criterion for simulating sand production using the finite element method. The porous medium was considered fully saturated. The onset of sanding and production of sand were predicted by coupling mechanical failure and subsequent erosion of the grain particles...
Numerical-probabilistic modeling of the liquefaction-induced free fields settlement
, Article Soil Dynamics and Earthquake Engineering ; Volume 149 , 2021 ; 02677261 (ISSN) ; Pak, A ; Pakzad, A ; Ayoubi, P ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
Liquefaction is a phenomenon through which saturated sandy soil loses its shear strength and turns into a liquefied state. One of the most detrimental consequences of liquefaction is the reconsolidation volumetric settlements after the earthquakes, which is due to the dissipation of excess pore pressure caused by earthquakes. Severe floods can follow these settlements in free fields such as grounds close to the sea or rivers. Several researchers studied this phenomenon using data obtained from experiments in the lab or observations in the fields. Previous works were mainly based on a limited number of experimental observations and considered loadings and boundary conditions that were...
Hybrid finite volume-finite element methods for hydro-mechanical analysis in highly heterogeneous porous media
, Article Computers and Geotechnics ; Volume 132 , 2021 ; 0266352X (ISSN) ; Ataie Ashtiani, B ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
In this study, two classes of advanced finite volume schemes, including Multi-Point Flux Approximation (MPFA) and Dual Discrete Finite Volume (DDFV) method, have been employed in conjunction with the finite element (FE) geomechanics simulator to model the coupled fluid-solid system. Fully saturated porous media with poroelastic behavior, random field permeability and elastic modulus are considered as parameters. The performance of the proposed hydro-mechanical models, including MPFA O-FEM and DDFV-FEM, is examined through different test cases. First, the models are validated and compared with the closed-form solutions in the homogeneous domain. Second, the methods' stability and convergence...
Impact of Hydraulic Hysteresis on Hydro-mechanical Behaviour of Infilled Fractured Rocks in Unsaturated Condition
, M.Sc. Thesis Sharif University of Technology ; Khosravi, Ali (Supervisor)
Abstract
Recent studies have shown that comprehensive characterization of the behavior of infilled rock fractures under saturated and unsaturated conditions requires knowledge of morphological details of fracture surface, as well as state of stress of infill materials and their initial innate conditions (e.g., void ratio, water content, degree of saturation and dry density). This study presents the details and typical results from a new testing approach to study the hydro-mechanical behavior of the infilled rock fractures under different stress states and saturation conditions. The new testing approach incorporates the axis translation technique for suction control, a flow pump for the measurement of...
Development of a model for Hydro-Mechanical Deep Drawing Process to Analyze the Effects of Assumptions and Parameters
, M.Sc. Thesis Sharif University of Technology ; Assempour, Ahmad (Supervisor)
Abstract
It is the goal of this thesis to develop an analytical model for the hydro-mechanical deep drawing (HDD) process of an axisymmetric sheet metal with the fixed gap method to evaluate the effects of some assumptions such as: proportional loading, plane stress, and constant thickness conditions. The effect of parameters on the HDD process is also studied. The main model is developed with considering the normal stress and part thickness change, non-proportional loading, bending and unbending effects at the top of the cup wall. The interrelationships between geometrical and mechanical variables are obtained in the finite difference form based on the incremental strain theory, thereby being solved...
Development of Unsaturated Triaxial Device in Order to Conduct Stress-Controlled Tests and Study of the Hydromechanical Behavior of Collapsible Soils under Anisotropic Consolidation Case Study: Loess of Gorgan
, M.Sc. Thesis Sharif University of Technology ; Haeri, Mohsen (Supervisor)
Abstract
Collapsible soils such as loess, which are naturally nearly dry or unsaturated, are problematic soils that experience significant decrease in volume when they are subjected to increasing moisture under loading. This type of soils are present in some parts of Iran such as province of Golestan. Most of the researches to date has tended to focus on measuring the values of collapse using conventional double oedometer. However, the study of hydromechanical behavior of this type of soils considering the effect of initial shear stress using unsaturated triaxial device has been rarely investigated by the researchers. The study on the unsaturated behavior of collapsible soils has started at Sharif...
Assessment of Initial Shear Stress Effect on Unsaturated Behavior of Reconstituted Collapsible Soils (A Case Study of the Gorgan Loess)
, M.Sc. Thesis Sharif University of Technology ; Haeri, Mohsen (Supervisor)
Abstract
Collapsible soils such as loess, are kinds of problematic soils which are found as the unsaturated state in nature. Due to strong inter-particle bonds, these soils have a high rather shear strength in their low water content. Upon wetting and under existence or absence of external loading these bonds are loose and soils structure undergo to collapse. These type of soils are found in various regions of Iran such as Gorgan plain. Despite previous studies in order to investigate the behavior of collapsible soils, but assessing the effect the anisotropic compression or initial shear stress on the hydromechanical behavior of these soils has been rarely investigated by the researchers. According...
A Micro-structural Study on Hydro-mechanical Behavior of Loess
, Ph.D. Dissertation Sharif University of Technology ; Jafarzadeh, Fardin (Supervisor) ; W. W. NG, Charles (Supervisor)
Abstract
Loess soil layers in semi-arid to arid areas have been deposited through the accumulation of aeolian sediments, resulted in a special metastable and open structure being usually unsaturated in nature. Since naturally occurred loess is widespread, it has been recently considered as a promising resource for constructing earth-fill structures. However, due to different microstructures of intact and recompacted loess, different responses to hydraulic and mechanical loading would be expected. Up to now, the hydro-mechanical behavior of loess from different perspectives has not been linked to its microstructural characteristics. The current research, therefore, aims to provide insight into the...
Thermo-Hydro-Mechanical Modeling of Fractured Porous Media with phase Change
, M.Sc. Thesis Sharif University of Technology ; Khoei, Amir Reza (Supervisor)
Abstract
The main goal of the research is to formulate and implement the governing equations of Thermo-Hydro-Mechanical (THM) phenomena in fractured/fracturing unsaturated porous media with two-phase fluid flow using the Extended Finite Element Method (XFEM)with phase change consideration(evaporation/condensation). The medium is assumed to be isotropic, and the fluid phases are liquid water, vapor and dry air. The four governing equations are linear momentum equilibrium of the media, continuity equation of water (liquid water and vapor), continuity equation of dry air, and the thermal equilibrium of the medium which are considered to be fully coupled. The fracture is modeled in mode I with...
Numerical Modeling of Thermo-Hydro-Mechanical Behavior of Deep Geothermal Reservoirs
, M.Sc. Thesis Sharif University of Technology ; Pak, Ali (Supervisor)
Abstract
All societies need energy to meet the basic needs of the people and to carry out the production processes. From 1850 onwards, the global use of fossil fuels (coal, oil and gas) for energy production increased, leading to a dramatic increase in the emission of carbon dioxide (CO2) into the atmosphere. Rising carbon dioxide and other greenhouse gases in the Earth's atmosphere and seeing adverse effects such as global warming have prompted the international community to replace fossil fuels with clean energy as much as possible. Geothermal energy as one of the clean, sustainable and extensive sources can be one of the available solutions to meet this need.Numerical modeling of geothermal...
Study of the Shear Stress Effect on the Behavior of Collapsible Soils and Introducing an Innovative Consecutive Model: “Three linear Stages” to Predict Behavior of Gorgan Loess
, M.Sc. Thesis Sharif University of Technology ; Haeri, Mohsen (Supervisor)
Abstract
In all five continents, existence of collapsible soils such as Loess has been reported. These kinds of soils have mutual properties such as open structure, high void ratio and low dry density. Collapsible soils are always at risk of experiencing significant reduction in volume due to increasing water content or degree of saturation. Hence, this kind of soil can lead to serious problems including reduce of load bearing capacity, excessive deformation and failure of foundations.Collapsible soils exist in several regions of Iran. Consequently, researching their properties is a key point of geotechnical studies in our country. Hence, in past 10 years, several studies have been conducted by...
Modeling of Enhanced Geothermal Systems Using XFEM Technique
, M.Sc. Thesis Sharif University of Technology ; Khoei, Amir Reza (Supervisor)
Abstract
In this study, a fully coupled thermo-hydro-mechanical model for modeling Enhanced geothermal systems (EGS) is introduced using the extended finite method for numerical solution. Enhanced geothermal systems are fractured porous media that in addition to the solid phase usually consist of one or more fluids. Heat extraction from Enhanced geothermal systems involves several Multiphysics coupling processes, including the seepage flow through the fractured porous media, the thermal exchange between the working fluid and the matrix, and the deformation of fractured porous media. modeling of these processes is complex and has several parameters. Therefore, a thermal-hydraulic-mechanical (THM)...
An extended finite element method for hydraulic fracture propagation in deformable porous media with the cohesive crack model
, Article Finite Elements in Analysis and Design ; Volume 73 , 2013 , Pages 77-95 ; 0168874X (ISSN) ; Khoei, A. R ; Sharif University of Technology
Abstract
In this paper, a fully coupled numerical model is developed for the modeling of the hydraulic fracture propagation in porous media using the extended finite element method in conjunction with the cohesive crack model. The governing equations, which account for the coupling between various physical phenomena, are derived within the framework of the generalized Biot theory. The fluid flow within the fracture is modeled using the Darcy law, in which the fracture permeability is assumed according to the well-known cubic law. By taking the advantage of the cohesive crack model, the nonlinear fracture processes developing along the fracture process zone are simulated. The spatial discretization...
Three-Dimensional Numerical Modeling of Oil Reservoir Stimulation by Hydraulic Fracturing Technique Using EFG Mesh-less Method and Considering Two-Phase Fluid Flow
, Ph.D. Dissertation Sharif University of Technology ; Pak, Ali (Supervisor)
Abstract
Hydraulic fracturing is a process during which a viscous fluid under relatively high pressure and flow rate is injected into a wellbore to induce and propagate a system of cracks in the ground.Hydraulic fracturing of underground formations has been widely used in different fields of
engineering, such as petroleum engineering, geotechnical engineering, environmental engineering, mining engineering,and so on.Despite the technological advances in the techniques of in-situ hydraulic fracturing, the industry lacks a realistic and reliable numerical model to design cost - effective and efficient hydraulic fracturing treatment.This is due to the complex interaction and strong coupling between...
engineering, such as petroleum engineering, geotechnical engineering, environmental engineering, mining engineering,and so on.Despite the technological advances in the techniques of in-situ hydraulic fracturing, the industry lacks a realistic and reliable numerical model to design cost - effective and efficient hydraulic fracturing treatment.This is due to the complex interaction and strong coupling between...
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 ; 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...
Fully Coupled Numerical Modeling Of CO2 Sequestration in Deep Underground Formations with EFG Method
,
M.Sc. Thesis
Sharif University of Technology
;
Pak, Ali
(Supervisor)
Abstract
Greenhouse gas emissions into the atmosphere have multiplied with the increase in fossil fuel consumption, which directly affects global warming. Global warming has other undesirable consequences such as rising sea water level and declining snow cover. To reduce greenhouse gases in the atmosphere, researchers have studied various ways, one of which is carbon dioxide injection into underground formations, which has a significant effect on reducing the amount of these gases in the atmosphere. Existence of high volume underground reservoirs with suitable conditions for gas injection to prevent gas escape has made it a widely used and effective method. Despite many advantages of this method, it...
The Study of the Effect of Geomechanical Parameters on Hydraulic Fracturing Characteristics in Hydrocarbon Reservoirs by Numerical Modeling
, M.Sc. Thesis Sharif University of Technology ; Pak, Ali (Supervisor)
Abstract
The exploitation of oil and gas were changed dramatically with the advent of hydraulic fracturing. By using enhanced oil recovery methods in unconventional reservoirs, USA could raise the rate of production in comparison with the rate of consumption. Hydraulic fracturing is one of the enhanced oil recovery methods.The purpose of this research is the study of the effects of geomechanical parameters in the characteristics of the cracks induced by hydraulic fracturing in unconventional oil reservoirs. The minimum in-situ stress and tensile stress of rock can be overcome by injecting fluid and thus the rock will be cracked. Changes in geomechanical parameters such as modulus of elasticity,...
Numerical Modeling of CO2 Sequestration in Nonhomogeneous (layered) Saline Underground Formations
, M.Sc. Thesis Sharif University of Technology ; Pak, Ali (Supervisor)
Abstract
Due to a rapid growth in the consumption of fossil fuels, the emission of greenhouse gases has multiplied in the atmosphere in the past few decades. This issue can directly affect on the rise of global temperature. Because of the intensification of the global warming, international organizations are looking for ways to reduce the greenhouse effect. One of these methods is injecting and trapping greenhouse gases, especially carbon dioxide, resulting from the operation of power plants and other large industries and preventing it from entering the atmosphere. The injection of carbon dioxide in underground salt water reservoirs can have various effects such as mechanical, hydraulic, thermal, and...
A coupled hydro-mechanical analysis for prediction of hydraulic fracture propagation in saturated porous media using EFG mesh-less method
, Article Computers and Geotechnics ; Vol. 55, issue , January , 2014 , p. 254-266 ; Pak, A ; Soga, K ; Sharif University of Technology
Abstract
The details of the Element Free Galerkin (EFG) method are presented with the method being applied to a study on hydraulic fracturing initiation and propagation process in a saturated porous medium using coupled hydro-mechanical numerical modelling. In this EFG method, interpolation (approximation) is based on nodes without using elements and hence an arbitrary discrete fracture path can be modelled.The numerical approach is based upon solving two governing partial differential equations of equilibrium and continuity of pore water simultaneously. Displacement increment and pore water pressure increment are discretized using the same EFG shape functions. An incremental constrained Galerkin...