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Quantitative risk assessment for wellbore stability analysis using different failure criteria

Alireza Noohnejad, Kaveh Ahangari, Kamran Goshtasbi
Journal PaperGeomechanics and Engineering , Volume 24 , Issue 3, 2021 January , {Pages 281-293 }

Abstract

Uncertainties in geomechanical input parameters which mainly related to inappropriate data acquisition and estimation due to lack of sufficient calibration information, have led wellbore instability not yet to be fully understood or addressed. This paper demonstrates a workflow of employing Quantitative Risk Assessment technique, considering these uncertainties in terms of rock properties, pore pressure and in-situ stresses to makes it possible to survey not just the likelihood of accomplishing a desired level of wellbore stability at a specific mud pressure, but also the influence of the uncertainty in each input parameter on the wellbore stability. This probabilistic methodology in conjunction with Monte Carlo numerical modeling technique

Calculation of Felicity ratio for phyllites specimens with different angles of anisotropy under uniaxial loading

Kamran Goshtasbi
Journal PaperKharazmi journal of earth sciences , Volume 6 , Issue 2, 2021 February 10, {Pages 0-0 }

Abstract

The utilize of Kaiser effect during acoustic emission testing is a novel approach for computing the amount of stress in the rock, which has been tremendously exploited due to the immense reduction in the cost and time of determining the in-situ stress. The Felicity ratio is a precise and appropriate criterion for assessing the accuracy in the evaluation of the Kaiser effect. Numerous factors influence the accuracy of the Kaiser effect. This paper investigates the effect of anisotropy on the Kaiser effect on the rock. For this purpose, acoustic emission effect in the unconfined compression test on the Phyllites specimens with various angles of anisotropy (0, 30, 60, and 90) has been conducted. The results demonstrate that in all unconfined c

Investigation of the Kaiser effect in anisotropic rocks with different angles by acoustic emission method

Mehdi Kharghani, Kamran Goshtasbi, Majid Nikkah, Kaveh Ahangari
Journal PaperApplied Acoustics , Volume 175 , 2021 April 1, {Pages 107831 }

Abstract

The utilize of Kaiser effect during acoustic emission testing is a novel approach for computing the amount of stress in the rock, which has been tremendously exploited due to the immense reduction in the cost and time of determining the in-situ stress. Several parameters influence the accuracy of the Kaiser effect. This paper investigates the effect of anisotropy on the Kaiser effect on the rock. For this purpose, acoustic emission effect in the uniaxial compression test and Brazilian tensile strength test on the Phyllites specimens with various angles of anisotropy (0, 30, 60, and 90?) has been conducted. The results demonstrate that in all uniaxial compression tests, the Felicity ratio of acoustic emission, which is defined as the ratio o

Simulation of hydraulic fracturing and Darcy fluid flow in a porous medium using a coupled Discrete Element Method with fluid flow

Ali Asghar Safari Varzaneh, Morteza Ahmadi, Kamran Goshtasbi
Journal PaperJournal of Petroleum Science and Engineering , 2021 March 24, {Pages 108706 }

Abstract

Studying fluid penetration of the rock matrix during fracture propagation is one of the most difficult technical challenges of hydraulic fracture engineering. To deal with this issue, a coupled hydraulic-mechanical model was performed to simulate fracture propagation during hydraulic fracturing. For this purpose, a new discrete elements approach with a force-displacement law was used for simulating the fracturing process in a flow-coupled Discrete Element Method (DEM). A series of cases was simulated to evaluate the effect of different rates of injection and permeability. Good agreement was obtained between the numerical results of this study and the reported experimental results. The results of hydraulic fracture modeling indicated that a

STRESS-DEPENDENCE OF THE PERMEABILITY, POROSITY, AND COMPRESSIBILITY OF FRACTURED CARBONATE ROCK

Parisa Bagherzadeh, Kamran Goshtasbi, Ezatallah Kazemzadeh
Journal PaperJournal of Porous Media , Volume 24 , Issue 5, 2021 January , {Pages }

Abstract

Although fractured reservoirs are important hydrocarbon resources, the increase in effective stress due to production causes fractures to be sealed and hence production rates decrease. A better understanding of permeability, porosity, and compressibility of fractures would be useful in optimizing production. This research paper describes experiments on carbonate fractured reservoir rocks by measuring the permeability, porosity, and compressibility of different types of fractures, based on their orientation, opening, density, and persistency. Fractured cylindrical rock samples from a south Iran oil reservoir were tested by helium gas apparatus in hydrostatic condition. Microscopic X-ray computerized tomography (CT) scanning was utilized to s

Stress-dependence of the permeability, porosity, and compressibility in fractured porous media regarding fracturing condition

Parisa Bagherzadeh, Kamran Goshtasbi, Ezatallah Kazemzadeh, Mojtaba Kashef, Hessam Aloki Bakhtiari
Journal PaperBulletin of Engineering Geology and the Environment , 2021 April 11, {Pages 19-Jan }

Abstract

Fractured reservoirs are important hydrocarbon resources. However, the production of hydrocarbon makes fractures to be sealed which in turn decreases the production rate. A better understanding of permeability, porosity, and compressibility of fractures would be useful in optimizing the production rate. This research paper explored stress-dependent permeability, porosity, and compressibility of fractured porous media, both experimentally and numerically. The laboratory results are used to calibrate numerical models. With this regard, the roles of fracturing parameters such as orientation, opening, fracture density, persistency, and the intersection of fractures on hydro-mechanical parameters of the fractured sample are analyzed

Scaling geological fracture network from a micro to a macro scale

Rouhollah Basirat, Kamran Goshtasbi, Morteza Ahmadi
Journal PaperFrattura ed Integrit? Strutturale , Volume 14 , Issue 51, 2020 January , {Pages 71-80 }

Abstract

Characterizing fracture systems at various scales, modeling fracture distributions, and clarifying scale relations that correlate total fracture systems are of paramount importance in geology, mining, civil engineering, and petroleum engineering. In this paper, the conditions of fracture network geometry are investigated in a field scale (about 100 m) and a core sample scale (several centimeters). To achieve this purpose, field surveys and coring of rock outcrops were performed in the Asmari Formation of Iran. Fractures were manually sampled from rock outcrops on the field scale while micro-fractures were surveyed using CT-scan images of core samples on a small scale. To compare the fracture network geometry, two perspectives of fractal dim

Identifying the geological hazards during mechanized tunneling in urban areas–the case of Tehran alluvium conditions

A Alebouyeh, AN Dehghan, K Goshtasbi
Journal PaperTunnels and Underground Cities: Engineering and Innovation Meet Archaeology, Architecture and Art: Volume 11: Urban Tunnels-Part 1 , 2020 May 22, {Pages 5264 }

Abstract

The current study addresses the various types of challenges and geological hazards during tunnel excavation by mechanized tunneling method (TBM) in Tehran Alluvium conditions. In addition to introduction of tunnel construction projects in the city of Tehran, challenges existing in their implementation along with strategy and solutions to deal with them, which are considered as valuable experiences of the projects, are described in this study. The results of this study showed that among the various hazards that occur during the excavation of a tunnel, eleven hazards are more important than other hazards, such as abrasion of the machine cutting tools, clogging around the machine cutting tools, soil mass displacement in the tunnel face, liquef

A new technical and economic model to calculate specific charge and specific drilling using hole diameter, height bench, uniaxial compressive strength, and joint set orientation

Ali Ghanizadeh Zarghami, Kourosh Shahriar, Kamran Goshtasbi, Afshin Akbari Dehkharghani
Journal PaperJournal of Mining and Environment , 2020 June 30, {Pages }

Abstract

Calculation of the specific charge and specific drilling before blasting operation play a significant role in blasting pattern design and reduction of the final extraction cost of minerals. Information from Sungun, Miduk and Chah-Firouzeh copper mines in Iran was assessed, and found that there is a significant relationship between specific charge and specific drilling with hole diameter, bench height, uniaxial compressive strength and joint set orientation and tested this model in Sungun copper mine. Due to insufficient consideration during the design of the blast pattern and because of the high hardness in the rock in some parts of the mine, lots of destructive events such as boulders, back break, bench toe, high specific charge and high s

Prediction of shear strain induced by blasting waves in surface structures based on coupled frequency, velocity, and displacement effects

Reza Nateghi, Kamran Goshtasbi, Hamid Reza Nejati
Journal PaperJournal of Vibration and Control , 2020 June 17, {Pages 1.0775463209e+15 }

Abstract

Blasting ground vibration is an undesirable side effect of using explosives to fragment rocks. There is not any universally accepted standard to determine limitations of blast vibrations; however, velocity is the most commonly used method to measure ground vibrations. Because the structural response is highly frequency dependent, the frequency content is an essential characteristic of blast-induced shock waves along with the velocity. The magnitude of blast-induced displacement or velocity and their relative stress and strain are directly related to the quantity of charge, distance from blasting point, and geological conditions. These effects were not considered in the response spectrum theory of structures. This article tries to propose a

Coupled Effects of Confining Pressure and Loading Rate on the Mechanical Behavior of Plastic Concrete

Reza Nateghi, Kamran Goshtasbi, Hamid Reza Nejati
Journal PaperJournal of Materials in Civil Engineering , Volume 32 , Issue 10, 2020 October 1, {Pages 04020292 }

Abstract

Plastic concrete is used widely in the construction of cut-off walls. These structures might be exposed to coupled effects of dynamic load along with confining pressure. Therefore, careful study of the impacts of these combined stress conditions is one of the primary issues to be considered in analysis and design. Although there is a large number of experiments on the mechanical properties of plastic concrete in static loading and triaxial condition, none have studied the behavior of this material in dynamic state loading. Therefore, a series of unconfined and triaxial compression tests has been carried out under different confining pressures and strain rates to experimentally investigate the behavior of this material under combined stress

Comprehensive mechanical earth modeling using well data

Alireza Noohnejad, Kaveh Ahangari, Kamran Goshtasbi
Journal PaperInnovative Infrastructure Solutions , Volume 6 , Issue 1, 2020 October 5, {Pages 13-Jan }

Abstract

Mechanical earth model is a numerical representation of the stress state, pore pressure and rock mechanical properties. While the different parameters in the MEM are interconnected in various ways, they fundamentally stem from the same basic set of log measurements. This paper demonstrates a scientific workflow to build a comprehensive well-centric MEM for a well in a carbonate reservoir in Persian Gulf and calibrate it via utilizing the existing data including LOT, MDT, drilling incidents, etc., to minimize the uncertainties related to data limitations. Finally, the calibrated MEM was used for sensitivity analysis of various wellbore trajectories and mud weight/pressure window for planning future wells and safe drilling in this underdevelo

Integrated mechanical earth model and quantitative risk assessment to successful drilling

Alireza Noohnejad, Kaveh Ahangari, Kamran Goshtasbi
Journal PaperJournal of Petroleum Exploration and Production Technology , 2020 October 20, {Pages 13-Jan }

Abstract

Use of vital geomechanical parameters for determination of safe mud pressure window is generally associated with high level of uncertainty primarily because of absence of sufficient calibration data including laboratory and field test information. The traditional deterministic wellbore stability analysis methodologies usually overlooked the uncertainty of these key parameters. This paper exhibits implementing a quantitative risk assessment technique on the basis of Monte-Carlo modeling to consider uncertainty from input data so as to make it possible to survey not just the likelihood of accomplishing a desired level of wellbore stability at a particular mud weight, but also the impacts of the uncertainty in each single parameter on the wel

Determination of plastic concrete behavior at different strain rates to determine Cowper-Symonds constant for numerical modeling

Reza Nateghi, Kamran Goshtasbi, Hamid Reza Nejati
Journal PaperComputers and Concrete , Volume 26 , Issue 3, 2020 January , {Pages 227-237 }

Abstract

Strain rate investigations are needed to calibrate strain-rate-dependent material models and numerical codes. An appropriate material model, which considers the rate effects, need to be used for proper numerical modeling. The plastic concrete cut-off wall is a special underground structure that acts as a barrier to stop or reduce the groundwater flow. These structures might be subjected to different dynamic loads, especially earthquake. Deformability of a structure subjected to dynamic loads is a principal issue which need to be undertaken during the design phase of these structures. The characterization of plastic concrete behavior under different strain rates is essential for proper designing of cut-off walls subjected to dynamic loads. T

A Numerical Investigation for TBM Disc Cutter Life Prediction in Hard Rocks

Masood Zahiri, Kamran Goshtasbi, Jafar Khademi Hamidi, Kaveh Ahangari
Journal PaperJournal of Mining and Environment , 2020 September 29, {Pages }

Abstract

There is a direct relationship between the efficiency of mechanized excavation in hard rocks and that of disc cutters. Disc cutter wear is an important effective factor involved in the functionality of tunnel boring machines. Replacement of disc cutters is a time-consuming and costly activity that can significantly reduce the TBM utilization and advance rate, and has a major effect on the total time and cost of the tunneling projects. When these machines bore through hard rocks, the cutter wear considerably affects the excavation process. To evaluate the performance of the cutters, first, it is essential to figure out how they operate the rock cutting mechanism; secondly, it is important to identify the key factors that cause the wear. In t

Umbrella arch method performance, structural behavior and design elements utilizing in collapsing zones

Parisa Bagherzadeh, Kamran Goshtasbi, Mojtaba Kashef
Journal PaperEnvironmental Earth Sciences , Volume 79 , Issue 23, 2020 December , {Pages 15-Jan }

Abstract

The umbrella arch method is a pre-reinforcement technique that ensures tunnel stability in poor ground conditions or shallow overburden. Quantitative assessment of this method is still challenging due to its complexity, there is no accurate method to model the behavior of reinforced arch forming with steel pipes and grout. This paper uses finite difference numerical simulation to model and analyze the effectiveness of the umbrella arch method in Qazvin–Rasht railway tunnel as well as in-situ measurement. Umbrella arch has modeled considering pipe, grout and soilcrete as pipe umbrella components; each pipe simulated individually. The structural behaviour of pipes in the excavation sequence is analyzed as well as the importance of geometri

On the effect of grain size on rock behavior under cyclic loading by distinct element method

ابوالفضل دلیرنسب, کامران گشتاسبی, کامران, نجاتی
Journal Paperروش های تحلیلی و عددی در مهندسی معدن , Volume 10 , Issue 25, 2020 December 21, {Pages 23-32 }

Abstract

It is well-known that the mechanical behavior of rocks under cyclic loading is much different from static loading conditions. In most constructions, the load applied to structures is within dynamic ranges. That’s why a great deal of attention has been paid to this field to identify the dynamic behavior of rocks in more detail. Nevertheless, the nature of dynamic failure in rocks has not yet been identified, particularly when it comes to cyclic loading The purpose of this study was to investigate the influence of grain size on the mechanical behavior of rocks under cyclic loading using numerical modeling by UDEC. A total of three grain-categories with a diameter of 1, 2, and 4 mm were modeled in the software. All models were of Brazilian t

A Numerical Investigation of TBM Disc Cutter Life Prediction in Hard Rocks

M Zahiri, K Goshtasbi, J Khademi Hamidi, K Ahangari
Journal Paper , , {Pages }

Abstract

A New Technical and Economic Model to Calculate Specific Charge and Specific Drilling Using Hole Diameter, Bench Height, Uniaxial Compressive Strength, and Joint Set Orientation

A Ghanizadeh Zarghami, K Shahriar, K Goshtasbi, ...
Journal Paper , , {Pages }

Abstract

Geomechanical key parameters of the process of hydraulic fracturing propagation in fractured medium

Rouhollah Basirat, Kamran Goshtasbi, Morteza Ahmadi
Journal PaperOil & Gas Science and Technology–Revue d’IFP Energies nouvelles , Volume 74 , 2019 June 21, {Pages 58 }

Abstract

Hydraulic Fracturing (HF) is a well-stimulation technique that creates fractures in rock formations through the injection of hydraulically pressurized fluid. Because of the interaction between HF and Natural Fractures (NFs), this process in fractured reservoirs is different from conventional reservoirs. This paper focuses mainly on three effects including anisotropy in the reservoir, strength parameters of discontinuities, and fracture density on HF propagation process using a numerical simulation of Discrete Element Method (DEM). To achieve this aim, a comprehensive study was performed with considering different situations of in situ stress, the presence of a joint set, and different fracture network density in numerical models. The analys

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