Stiff String Casing Design: Tortuosity and Centralisation

2021 ◽  
Author(s):  
Benjamin Nobbs ◽  
Florian Aichinger ◽  
Ngoc-Ha Dao ◽  
Regis Studer
Keyword(s):  
Stress State ◽  
Axial Stress ◽  
String Model ◽  
Additional Stress ◽  
Radial Clearance ◽  
Drilling Process ◽  
Bending Stress ◽  
Drag Model ◽  
Contact Points ◽  
Casing Wear

Abstract The forces and stresses along casing strings are modeled using a stiff string torque and drag model. The effect of wellbore tortuosity and centralization are quantified in preplanning phase in addition to the effect of 3D orientated casing wear. A realistic case study is presented to show the resulting effect on axial, burst, collapse and Von Mises equivalent (VME) safety factor as well as VME body and connection design envelopes. While running a tubular downhole, a smooth wellbore is normally assumed when performing a torque and drag calculation. In reality, the inherent tortuosity of the wellbore which is caused by the drilling process can cause significant local doglegs. When applying a soft-string torque and drag model, the stiffness, radial clearance and high frequency surveys needed to fully model local doglegs are rarely modeled. The stiff string torque and drag and buckling model can model these effects, as well as the addition of rigid and flexible centralisers. This study involves the comparison of different casing design load cases, under different centralizer programs and tortuosity taking into account a 3D orientated casing wear. The results show that there can be significant differences in overall axial stress depending on the centraliser program and tortuosity used. The soft string model doesn't directly account for bending stress, normally this is estimated using a Bending Stress Magnification Factor (BSMF). In contract the stiff string model can directly calculate the additional bending stress. This additional stress can be particularly prevalent while RIH casing with centralisers and high tortuosity. The reduction in American Petroleum Institute (API) and VME stress envelope is also quantified using a 3D orientated casing wear model. A better understanding of axial stress state reduces risk of well integrity issues. This paper will show the benefits of using a stiff string model, considering additional contact points, bending stress as well as the benefits of modelling tortuosity and centralizer program early in the design process. During extended reach drilling (ERD) and high-pressure, high temperature (HPHT) wells, this information can be critical when correctly assessing the axial stress state.

scholarly journals Non-destructive Assessment of the Axial Stress State in Iron and Steel Truss Structures by Dynamic Measurements

2017 ◽  
Vol 199 ◽  
pp. 3380-3385 ◽  
Author(s):  
Hoa T.M. Luong ◽  
Volkmar Zabel ◽  
Werner Lorenz ◽  
Rolf G. Rohrmann
Keyword(s):  
Stress State ◽  
Axial Stress ◽  
Truss Structures ◽  
Dynamic Measurements ◽  
Iron And Steel ◽  
Steel Truss ◽  
Non Destructive

Application of Large Size and High Strength Angle in UHV Transmission Line Tower

2014 ◽  
Vol 680 ◽  
pp. 418-421
Author(s):  
Feng Lin Gan ◽  
Xin Wang
Keyword(s):  
Transmission Line ◽  
Axial Stress ◽  
High Strength ◽  
Additional Stress ◽  
Large Size ◽  
Section Area ◽  
Stiffness Variation ◽  
Large Width ◽  
Angle Steel ◽  
Normal Angle

Considering width and thickness of large width angle steel, the section area of large width angle steel is larger than that of normal angle steel. Application of large width angle can increase bearing capacity of the member. Therefore it is feasible that large width angle steel replaces double combined angle steels. Taking the tower for ±800 kV DC transmission line from Jin ping to south Jiangsu Province, under the same design conditions, large width angle steel and double combined angle steels are used respectively in the main members of the tower to modeling finite element analysis.The results indicate that the stiffness variation is more uniform, causing rod end bending bar additional stress is about the axial stress of about 2%~3%.

Neutron Evaluation of Stress in Industrial Screws

2005 ◽  
Vol 490-491 ◽  
pp. 269-274
Author(s):  
Agnès Fabre ◽  
Ivan Lillamand ◽  
Jean-Éric Masse ◽  
Laurent Barrallier
Keyword(s):  
Stress State ◽  
Service Life ◽  
Neutron Diffraction ◽  
Axial Stress ◽  
Stress Gradient ◽  
In Situ Measurements ◽  
Nondestructive Technique

Neutron diffraction measurements were used in this study in order to determine the axial stress state in loaded screw from a specific assembly. The knowing of stress gradient is need to qualify a standard gauge used to calibrate the response of in-situ measurements using ultrasonic nondestructive technique. US is well adapted to perform measurements of the evolution of stress state on industrial screws during service life of the bolded assemblies.

scholarly journals Prediction of fatigue limit of journal bearings considering a multi-axial stress state

2016 ◽  
Vol 68 (3) ◽  
pp. 430-438 ◽  
Author(s):  
Christopher Sous ◽  
Henrik Wünsch ◽  
Georg Jacobs ◽  
Christoph Broeckmann
Keyword(s):  
Stress State ◽  
Axial Stress ◽  
Design Guidelines ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Test Results ◽  
Content Type ◽  
Operation Conditions ◽  
Component Test ◽  
Material Tests

Purpose The purpose of this paper is to investigate the applicability of the quadratic failure hypothesis (QFH) on journal bearings coated with a white metal sliding layer on the prediction of safe and unsafe operating conditions. The hypothesis covers operation conditions under static and dynamical loading. Design/methodology/approach Material tests and elastohydrodynamic, as well as structural, simulations were conducted to provide the required input data for the failure hypothesis. Component samples were tested to verify the results of the QFH. Findings The load bearing capacity of journal bearings was analysed for different operating conditions by the use of the QFH. Results allow for the identification of critical and non-critical loading conditions and are in accordance with component test results. Originality/value Today’s design guidelines for journal bearings do not consider a multi-axial stress state and actual stress distribution. The applied hypothesis enables consideration of multiaxiality inside the sliding surface layer, as well as determining the location of bearing fatigue due to material overload.

scholarly journals Fault model of the 2012 doublet earthquake, near the up-dip end of the 2011 Tohoku-Oki earthquake, based on a near-field tsunami: implications for intraplate stress state

2019 ◽  
Vol 6 (1) ◽  
Author(s):  
Tatsuya Kubota ◽  
Ryota Hino ◽  
Daisuke Inazu ◽  
Syuichi Suzuki
Keyword(s):  
Stress State ◽  
Frictional Coefficient ◽  
Fault Model ◽  
Japan Trench ◽  
Time Interval ◽  
Depth Range ◽  
Seismic Zone ◽  
Bending Stress ◽  
Normal Faulting ◽  
Brittle Strength

AbstractOn December 7, 2012, an earthquake occurred within the Pacific Plate near the Japan Trench, which was composed of deep reverse- and shallow normal-faulting subevents (Mw 7.2 and 7.1, respectively) with a time interval of ~10 s. It had been known that the stress state within the plate was characterized by shallow tensile and deep horizontal compressional stresses due to the bending of the plate (bending stress). This study estimates the fault model of the doublet earthquake utilizing tsunami, teleseismic, and aftershock data and discusses the stress state within the incoming plate and spatiotemporal changes seen in it after the 2011 Tohoku-Oki earthquake. We obtained the vertical extents of the fault planes of deep and shallow subevents as ~45–70 km and ~5 (the seafloor)–35 km, respectively. The down-dip edge of the shallow normal-faulting seismic zone (~30–35 km) deepened significantly compared to what it was in 2007 (~25 km). However, a quantitative comparison of the brittle strength and bending stress suggested that the change in stress after the Tohoku-Oki earthquake was too small to deepen the down-dip end of the seismicity by ~10 km. To explain the seismicity that occurred at a depth of ~30–35 km, the frictional coefficient in the normal-faulting depth range required would have had to be ~0.07 ≤ μ ≤ ~0.2, which is significantly smaller than the typical friction coefficient. This suggests the infiltration of pore fluid along the bending faults, down to ~30–35 km. It is considered that the plate had already yielded to a depth of ~35 km before 2011 and that the seismicity of the area was reactivated by the increase in stress from the Tohoku-Oki earthquake.

scholarly journals Investigation of the Residual Stress State in an Epoxy Based Specimen

2015 ◽  
Vol 651-653 ◽  
pp. 375-380
Author(s):  
Ismet Baran ◽  
Johnny Jakobsen ◽  
Jens H. Andreasen ◽  
Remko Akkerman
Keyword(s):  
Elastic Modulus ◽  
Stress State ◽  
Residual Stresses ◽  
Process Model ◽  
Coefficient Of Thermal Expansion ◽  
Numerical Models ◽  
Mechanical Analysis ◽  
Biaxial Stress ◽  
Image Correlation ◽  
Drilling Process

Process induced residual stresses may play an important role under service loading conditions for fiber reinforced composite. They may initiate premature cracks and alter the internal stress level. Therefore, the developed numerical models have to be validated with the experimental observations. In the present work, the formation of the residual stresses/strains are captured from experimental measurements and numerical models. An epoxy/steel based sample configuration is considered which creates an in-plane biaxial stress state during curing of the resin. A hole drilling process with a diameter of 5 mm is subsequently applied to the specimen and the released strains after drilling are measured using the Digital Image Correlation (DIC) technique. The material characterization of the utilized epoxy material is obtained from the experimental tests such as differential scanning calorimetry (DSC) for the curing behavior, dynamic mechanical analysis (DMA) for the elastic modulus evolution during the process and a thermo-mechanical analysis (TMA) for the coefficient of thermal expansion (CTE) and curing shrinkage. A numerical process model is also developed by taking the constitutive material models, i.e. cure kinetics, elastic modulus, CTE, chemical shrinkage, etc. together with the drilling process using the finite element method. The measured and predicted in-plane residual strain states are compared for the epoxy/metal biaxial stress specimen.

A Model for Determining Crack Opening Stress Intensity Factor Ratio under Tri-Axial Stress State

2005 ◽  
Vol 297-300 ◽  
pp. 1572-1578
Author(s):  
Yu Ting He ◽  
Feng Li ◽  
Rong Shi ◽  
G.Q. Zhang ◽  
L.J. Ernst ◽  
...  
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Stress State ◽  
Intensity Factor ◽  
Present Model ◽  
Axial Stress ◽  
Crack Opening ◽  
Factor Ratio ◽  
Crack Opening Stress ◽  
Good Agreement

When studying 3D fatigue crack growth behaviors of materials, to determine the crack opening stress intensity factor ratio is the key issue. Elastic-plastic Fracture Mechanics theory and physical mechanism of cracks’ closure phenomena caused by plastic deformation are employed here. A model for determining the crack opening stress intensity factor ratio under tri-axial stress state is presented. The comparison of the present model with available data and models shows quite good agreement.

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