Numerical Investigation of Vertical Penetration of Steel Catenary Riser Near the Touch Down Zone

2016 ◽  
Author(s):  
Sujan Dutta ◽  
Bipul Hawlader ◽  
Ryan Phillips ◽  
Mike Paulin
Keyword(s):  
Soft Clay ◽  
Sea Waves ◽  
Factors Affecting ◽  
Steel Catenary Riser ◽  
Rate Dependent ◽  
Physical Experiments ◽  
Ansys Cfx ◽  
Waves And Currents ◽  
Steel Catenary Risers ◽  
Uplift Resistance

Steel catenary risers (SCR) are widely used in offshore to transport hydrocarbon from the seabed to floating or fixed platforms. The fatigue life of SCR near the touchdown zone (TDZ) is one of the main design concerns because the risers are often subjected to cyclic loading (vertical penetration/uplift, lateral and axial displacements) from various sources of environmental loadings, such as sea waves and currents. Numerical modeling of the penetration and uplift behaviour of an SCR is a challenging task. Most of the models available in the literature for uplift resistance are empirical, which have been developed mainly from the results of physical experiments. In this study, numerical simulation of vertical resistance is presented. Analysis is performed using ANSYS CFX software. Strain-softening and strain-rate dependent undrained shear strength behavior of soft clay sediment has been reported by many researchers. Unfortunately, these models were not available in CFX. Numerical simulations presented in this paper are performed implementing this behavior in CFX. Numerical results are compared with available empirical models. The present CFX modeling explains some mechanisms involved in trench formation and suction development during uplift. Factors affecting uplift resistance such as the size and shape of the trench are also discussed from a parametric study.

Dynamic Optimization of Steel Catenary Risers Based on Reliability Using Metamodel

2010 ◽  
Author(s):  
Wenqing Zheng ◽  
Hezhen Yang
Keyword(s):  
Dynamic Optimization ◽  
Computational Cost ◽  
Minimum Cost ◽  
Probabilistic Constraints ◽  
Optimization Approach ◽  
Element Analysis ◽  
Steel Catenary Riser ◽  
Reliability Based Design ◽  
Minimum Cost Design ◽  
Steel Catenary Risers

Reliability based design optimization (RBDO) of a steel catenary riser (SCR) using metamodel is investigated. The purpose of the optimization is to find the minimum-cost design subjecting to probabilistic constraints. To reduce the computational cost of the traditional double-loop RBDO, a single-loop RBDO approach is employed. The performance function is approximated by using metamodel to avoid time consuming finite element analysis during the dynamic optimization. The metamodel is constructed though design of experiments (DOE) sampling. In addition, the reliability assessment is carried out by Monte Carlo simulations. The result shows that the RBDO of SCR is a more rational optimization approach compared with traditional deterministic optimization, and using metamodel technique during the dynamic optimization process can significantly decrease the computational expense without sacrificing accuracy.

Sensitivity Study of Critical Parameters Influencing the Uncertainty of Fatigue Damage in Steel Catenary Risers

2010 ◽  
Author(s):  
Feng Zi Li ◽  
Ying Min Low
Keyword(s):  
Fatigue Damage ◽  
Cost Effective ◽  
Sensitivity Study ◽  
Structural Safety ◽  
Critical Parameters ◽  
Design Parameters ◽  
Steel Catenary Riser ◽  
Bending Stresses ◽  
Steel Catenary Risers ◽  
Touchdown Point

The most challenging aspect of a deepwater development is the riser system, and a cost-effective choice is the Steel Catenary Riser (SCR). Fatigue is often a governing design consideration, and it is usually most critical at the touchdown point (TDP) where static and dynamic bending stresses are highest. Unfortunately, it is also at this region that uncertainty is the maximum. The increased uncertainty casts doubt on the applicability of generic safety factors recommended by design codes, and the most consistent way of ensuring the structural safety of the SCR is to employ a reliability-based approach, which has so far not received attention in SCR design. As the number of basic random variables affects the complexity of a reliability analysis, these variables should be selected with caution. To this end, the aim of this paper is to draw up a comprehensive list of design parameters that may contribute meaningfully to the uncertainty of the fatigue damage. From this list, several parameters are selected for sensitivity studies using the commercial package Orcaflex. It is found that variations in seabed parameters such as soil stiffness, soil suction and seabed trench can have a pronounced influence on the uncertainty of the fatigue damage at the touchdown point.

scholarly journals Experimental Analyses of the Major Parameters Affecting the Intensity of Outbursts of Coal and Gas

2014 ◽  
Vol 2014 ◽  
pp. 1-9
Author(s):  
W. Nie ◽  
S. J. Peng ◽  
J. Xu ◽  
L. R. Liu ◽  
G. Wang ◽  
...  
Keyword(s):  
Water Content ◽  
Relative Intensity ◽  
Gas Content ◽  
Horizontal Load ◽  
Vertical Load ◽  
Range Analysis ◽  
Factors Affecting ◽  
Mining Depth ◽  
Physical Experiments ◽  
Relative Threshold

With an increase in mining depth and production, the intensity and frequency of outburst of coal and gas have a tendency to increase. Estimating the intensity of outbursts of coal and gas plays an important role because of its relation with the risk value. In this paper, we described the semiquantitative relations between major parameters and intensity of outburst based on physical experiments. The results showed increment of geostress simulated by horizontal load (from 1.4, 2.4, 3.2, to 3.4 MPa) or vertical load (from 2, 3, 3.6, to 4 MPa) improved the relative intensity rate (3.763–7.403% and 1.273–7.99%); the increment of porosity (from 1.57, 2.51, 3, to 3.6%) improved the relative intensity rate from 3.8 to 13.8%; the increment of gas pressure (from 0, 0.5, 0.65, 0.72, 1, to 1.5 Mpa) induced the relative intensity rate to decrease from 38.22 to 0%; the increment of water content (from 0, 2, 4, to 8%) caused the relative intensity rate to drop from 5.425 to 0.5%. Furthermore, sensitivity and range analysis evaluates coupled factors affecting the relative intensity. In addition, the distinction with initiation of outburst of coal and gas affected by these parameters is discussed by the relative threshold of gas content rate.

A Parametric Study for the Design of Steel Catenary Riser System in Deepwater Harsh Environments

2008 ◽  
Author(s):  
Jie Xia ◽  
Purnendu K. Das ◽  
Daniel Karunakaran
Keyword(s):  
Parametric Study ◽  
Computer Time ◽  
Harsh Environments ◽  
Analysis Tool ◽  
Primary Analysis ◽  
Steel Catenary Riser ◽  
Analysis Process ◽  
Steel Catenary Risers ◽  
Northern North Sea

In recent years, offshore reservoirs have been developed in deeper and deeper water environments, where floating production, storage and offloading (FPSO), semi-submersibles, spars and TLPs are considered to be the most economically viable platforms. Steel catenary risers (SCRs) are being considered for these production units in deepwater development such as Northern North Sea. A variety of uncertainties are associated with material behaviour, environmental loading, hydromechanics modelling, structural modelling, and fatigue / corrosion / wear characteristics, especially around hang-off and touch down areas. SCRs used in conjunction with a semi-submersible or a FPSO in deepwater harsh environments present significant design challenges. The large vertical motions at the FPSO or semi induce severe riser response, which results in difficulty meeting strength and fatigue criteria at the hang-off and touch down point locations. To improve the understanding of SCR behaviour and increase the confidence in the design of such systems in deepwater harsh environments, a parametric study was carried out in this paper to deal with the factors that mainly influence the loading condition and fatigue life of the riser. Two cases, one steel catenary riser connected to a semi-submersible and one steel catenary riser connected to a FPSO, were studied and compared. And weight-optimized configurations were applied for both risers. Riflex combined with DeepC was the primary analysis tool used for the long-term response of the nonlinear structure SCR’s simulations, which is high computer time consuming. Hence, the parameters affecting the efficiency and accuracy of the simulations have also been studied during the analysis process.

Process-Structure-Property Fatigue Characterisation for Welding of X100 Steel Catenary Risers

2019 ◽  
Author(s):  
Ronan J. Devaney ◽  
Adrian Connaire ◽  
Padraic E. O’Donoghue ◽  
Sean B. Leen
Keyword(s):  
Weld Metal ◽  
Fatigue Testing ◽  
Weld Zone ◽  
Parent Material ◽  
Strain History ◽  
Structure Property ◽  
Steel Catenary Riser ◽  
Thermomechanical Simulation ◽  
Steel Catenary Risers ◽  
Process Structure

Abstract Welded connections are a fatigue sensitive location for offshore steel catenary risers. The susceptibility to fatigue is due to the notch effect of the weld and the gradient in microstructure and material properties across the weld which result from welding thermal cycles and differences in the composition of the parent material and weld metal. In this work, a representative full-scale steel catenary riser girth weld is conducted using X100Q steel. The thermal and strain history in the weld zone are captured using a thermocouple and strain gauge array. A parallel programme of Gleeble thermomechanical simulation is implemented to develop microstructurally uniform heat affected zone (HAZ) test specimens. The parent material, weld metal, simulated HAZ and a cross-weld sample are characterised using a programme of nanoindentation, tensile and fatigue testing. A softened region with microstructure corresponding to intercritical HAZ (ICHAZ) is identified in the girth weld. Tensile and fatigue failures are shown to occur in a representative microstructural region for simulated HAZ specimens, indicating a susceptibility to failure in the ICHAZ for matched or over-matched X100Q welds.

Model Test of a Steel Catenary Riser in a Towing Tank

2009 ◽  
Author(s):  
Celso K. Morooka ◽  
Raphael I. Tsukada ◽  
Sergio da Silva ◽  
Ricardo Franciss ◽  
Cyntia G. C. Matt
Keyword(s):  
Model Test ◽  
Forced Oscillation ◽  
Cross Flow ◽  
Towing Tank ◽  
Steel Catenary Riser ◽  
Flow Response ◽  
Numerical Predictions ◽  
Steel Catenary Risers ◽  
Numerical Tools ◽  
Scr Model

The objective of the present work is the study of the dynamic behavior of steel catenary risers (SCRs), focusing on the contribution of vortex-induced vibration (VIV), through model test in a towing tank. Nowadays, a great deal of effort is being spent in order to better understand VIV’s contribution in the dynamics of riser structures through experiments, analytical analysis and numerical predictions. In the present work, the design of a SCR model test, along with its setup in a towing tank, will be described in detail and discussions of main results from the experiments will be presented. The experiment has been conducted under several simulated environmental condition combinations, varying the towing speed, riser top forced oscillation amplitudes, waves amplitudes and periods. Very promising results have been observed from the experiment. Riser oscillations due to high harmonics of vortex shedding were observed. Analysis of the experimental results, coupled with the support of numerical tools, showed the influence of the phenomena of traveling waves in the cross-flow response as is reported from the literature.

Compression Assessment of Deepwater Steel Catenary Risers at Touch Down Zone

2007 ◽  
Author(s):  
Yongming Cheng ◽  
Ruxin Song ◽  
Basim Mekha ◽  
Andrew Torstrick ◽  
Hugh Liu
Keyword(s):  
Failure Modes ◽  
Nonlinear Finite Element ◽  
Nonlinear Finite Element Method ◽  
Short Term ◽  
Shell Elements ◽  
Steel Catenary Riser ◽  
Compression Load ◽  
Steel Catenary Risers ◽  
Significant Compression ◽  
The Time Domain

A steel catenary riser (SCR) is a widely used concept for deepwater floating production facilities. Severe motions of a floating host facility such as a semisubmersible or FPSO may cause a significant compression load on SCRs at the touch down zone (TDZ). This paper investigates how to assess the compression that could be experienced by deepwater SCRs, including methodology, failure modes considered, acceptance criteria, computer modeling, and describe the steps necessary for assessing the compression forces. To demonstrate the proposed methodology and criteria, a recent example of the Independence Hub 20-inch Gas Export SCR in ultra deepwater (i.e. 8,000 ft) is given to illustrate the compression and buckling phenomenon. The behavior of the SCR compression and buckling at the TDZ is investigated by using a nonlinear finite element method to determine the mechanism and governing factors. Both beam and shell elements are used in the detailed analysis for comparison purposes. In addition a strain-based criterion is implemented to determine if the compression level is acceptable. Short term fatigue damage is also calculated by using the time domain rain-flow method. In general, the paper presents an analysis procedure outlining the steps necessary for evaluating the compression and buckling phenomenon of deepwater SCRs.

Fatigue Life Analysis for a Steel Catenary Riser in Ultra-Deep Waters

2012 ◽  
Author(s):  
Marcos V. Rodrigues ◽  
Caroline Ferraz ◽  
Danilo Machado L. da Silva ◽  
Bruna Nabuco
Keyword(s):  
Fatigue Life ◽  
Global Analysis ◽  
Fatigue Behavior ◽  
Density Variation ◽  
Steel Catenary Riser ◽  
Deep Waters ◽  
Internal Fluid ◽  
Steel Catenary Risers ◽  
Fatigue Life Analysis ◽  
Definition Of

With new discoveries in the Brazilian Pre-Salt area, the oil industry is facing huge challenges for exploration in ultra-deep waters. The riser system, to be used for the oil transportation from seabed to the production unit, is one of them. The definition of riser configurations for ultra-deep waters is a real challenge. Problems have being identified for flexible risers, hybrid risers and steel catenary risers (SCR) configurations to comply with rules requirements and criteria in water depths of 2000m. The objective of this work is to present a study on the fatigue behavior of a Steel Catenary Riser in 1800m of water depth. One of the main challenges for SCRs in ultra-deep waters is the fatigue, due to platform 1st order motions, at the touch down zone (TDZ). A case study is presented for a Steel Catenary Riser connected to a semi-submersible platform. The influence of some design and analysis parameters is studied in order to evaluate their impact on the SCR fatigue life. The main parameters to be evaluated in this work are: The mesh refinement, in the global analysis, at the Touch Down Zone; The internal fluid density variation along the riser, and; The 1st order platform motions applied to the top of riser; In addition to the results of this paper, some highlights are presented for SCR analysis in similar conditions.

VSIV (Vortex Self-Induced Vibration) Kinematics

2008 ◽  
Author(s):  
Antonio C. Fernandes ◽  
Erika M. C. Silva ◽  
Ricardo Franciss ◽  
Fabio M. Coelho ◽  
Severino F. S. Neto
Keyword(s):  
Graduate School ◽  
Transverse Direction ◽  
Horizontal Cylinder ◽  
Forced Oscillations ◽  
Lateral Motion ◽  
Steel Catenary Riser ◽  
The Past ◽  
Waves And Currents ◽  
Dimensional Parameters ◽  
A Current

The Vortex Induced Vibration (VIV) of cylindrical lines that may occur when the lines are submitted to currents has been extensively discussed in the past few years and its behavior has become well known. However, it is not so well known that the vibrations may occur in a current-less situation, induced by the lateral motion of the structure itself. The present work refers to the last as the Vortex Self-Induced Vibration, the VSIV. This occurrence has been made clear in the LOC/COPPE/UFRJ (Laboratory of Waves and Currents of COPPE, the Graduate School of Federal University of Rio de Janeiro) by specifically designed tests. In these tests, a totally submerged horizontal cylinder was submitted to harmonic forced oscillations, being free to move in the transverse direction of the forced excitation. The VSIV then showed up, with the cylinder segment, describing vertical trajectories in two (vertical 8-shape), three, four, etc., almost circular trajectories (called the rings in the work). Subsequently, the work shows that the measurements in full scale with the VIV bottle on a Steel Catenary Riser in the PETROBRAS 18 platform also indicate the existence of the VSIV. The tests were carried out with Keulegan-Carpenter equal to 10, 20 and 30 and for several amplitudes. The response of the cylinder was represented in non-dimensional parameters corresponding to the amplitude, the excitation and the response frequencies.

scholarly journals A Study on Evacuation Behavior in Physical and Virtual Reality Experiments

2021 ◽  
Author(s):  
Silvia Arias ◽  
Axel Mossberg ◽  
Daniel Nilsson ◽  
Jonathan Wahlqvist
Keyword(s):  
Virtual Reality ◽  
Virtual Environment ◽  
Waiting Times ◽  
Physical Experiment ◽  
Evacuation Time ◽  
Factors Affecting ◽  
Head Mounted Display ◽  
Physical Experiments ◽  
Exit Choice ◽  
In Fire

AbstractComparing results obtained in Virtual Reality to those obtained in physical experiments is key for validation of Virtual Reality as a research method in the field of Human Behavior in Fire. A series of experiments based on similar evacuation scenarios in a high-rise building with evacuation elevators was conducted. The experiments consisted of a physical experiment in a building, and two Virtual Reality experiments in a virtual representation of the same building: one using a Cave Automatic Virtual Environment (CAVE), and one using a head-mounted display (HMD). The data obtained in the HMD experiment is compared to data obtained in the CAVE and physical experiment. The three datasets were compared in terms of pre-evacuation time, noticing escape routes, walking paths, exit choice, waiting times for the elevators and eye-tracking data related to emergency signage. The HMD experiment was able to reproduce the data obtained in the physical experiment in terms of pre-evacuation time and exit choice, but there were large differences with the results from the CAVE experiment. Possible factors affecting the data produced using Virtual Reality are identified, such as spatial orientation and movement in the virtual environment.

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