Investigation of VIV Fatigue Prediction for a Top Tensioned Riser

2009 ◽  
Author(s):  
Yongming Cheng ◽  
Lixin Xu ◽  
Kostas F. Lambrakos ◽  
Karl Muriby
Keyword(s):  
Production Systems ◽  
Direct Access ◽  
Mode Shapes ◽  
Floating Platform ◽  
Finite Element Program ◽  
Prediction Program ◽  
Mode Cutoff ◽  
Element Program ◽  
Offshore Industry ◽  
The Time Domain

Top tensioned risers (TTRs) have been widely used with floating production systems such as Spars and TLPs in deepwater field developments. A TTR system provides direct access to subsea wellheads from a floating platform for drilling, workover, and completion operations. It is often subjected to Vortex-Induced Vibrations (VIVs) caused by ambient ocean currents. This paper investigates the VIV fatigue prediction for a TTR used with a Spar in deep water. The riser VIV predictions are mainly based on the frequency domain program SHEAR7 that is widely used in the offshore industry. The nonlinear finite element program ABAQUS is used to model the riser for the generation of modal data, including natural frequencies, mode shapes and mode curvatures. The riser is modeled using generic beam elements with equivalent section properties. The model considers the lateral supports from the keel guide and hard tank. The riser tensioner is modeled with non-linear springs. The riser VIV is predicted using different SHEAR7 versions. This paper investigates the sensitivity of the results to key parameters such as the type of lift coefficients, mode bandwidth, mode cutoff, and the Strouhal number. In addition, the time domain VIV prediction program ABAVIV is used to compute the VIV response for a few governing current profiles. The results by SHEAR7 are compared with those by ABAVIV.

Time Domain VIV Prediction for Top Tensioned Risers

2010 ◽  
Author(s):  
Yongming Cheng ◽  
Kostas F. Lambrakos ◽  
Roger Burke ◽  
Paul Stanton
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Production Systems ◽  
Vertical Direction ◽  
Direct Access ◽  
Frequency Domain Method ◽  
Floating Platform ◽  
Prediction Program ◽  
Use Of Time ◽  
The Time Domain

Top Tensioned Risers (TTRs) have been widely used with floating production systems such as Spars and TLPs in deepwater field developments. A TTR system provides direct access to subsea wells from a floating platform for drilling, workover, and completion operations. It is often subjected to Vortex-Induced Vibration (VIV) caused by ambient ocean currents or vessel motions. This paper investigates time domain VIV prediction for TTRs used in a typical Spar floating production system. A typical TTR has strong nonlinear and time-varying dynamic characteristics. The existing gaps between the riser and keel guide and between riser top centralizers and the supporting conductor result in intermittent VIV behaviors of the riser. In addition, hydraulic tensioners are widely used to provide tension to a TTR. The tension from tensioners varies with the riser’s dynamic response especially in the vertical direction. The time domain approach, which has been benchmarked and published in about ten technical papers, is thus more appropriate to predict TTRs’ VIV performance than a frequency domain method. This paper first introduces a typical TTR structure and then presents the analysis methodology and features of the time domain VIV prediction program ABAVIV. An example TTR is used to illustrate intermittent VIV behaviors such as top tension, interaction load at the keel guide, and VIV response at the location of top centralizers. This paper further studies the sensitivity of the VIV response to different current profiles. It finally uses the time domain approach to analyze the VIV response of the riser with its boundary conditions fixed and compares the results with those from a frequency domain program. A conclusion is finally drawn about the use of time domain VIV prediction for Spar TTRs.

Investigation of Impact of New Design Code on Riser System Design

2009 ◽  
Author(s):  
Alan Yu ◽  
Paul Stanton ◽  
Yongming Cheng
Keyword(s):  
System Design ◽  
Production Systems ◽  
Design Code ◽  
Finite Element Program ◽  
Stress Evaluation ◽  
Element Program ◽  
Steel Catenary Risers ◽  
Ease Of Access ◽  
The Impact ◽  
Gas Lift

Top tensioned risers are fluid conduits from subsea equipment to surface floating production platforms. The advantages of using top tensioned risers are the ability to drill and complete through the production riser, ease of access of the production trees for gas lift operation, and the simplicity of workover and redrill. The integrity of a riser system plays an important role in deepwater developments. Top tensioned risers (TTRs) and steel catenary risers (SCRs) have been widely used with floating production systems such as Spars and TLPs. API RP 2RD [1] has been used to guide riser system design for the last decade. API RP 2RD is being revised as a code (ISO 13628-12) that will also be adopted as a new API code. This paper investigates the impacts of the new design code on the riser system design. This paper first discusses the differences between ISO/WD 13628-12 and the existing API RP 2RD code, particularly the section on design criteria for pipes. The Holstein top tensioned riser system is chosen as an example to evaluate the riser system design impacts. The risers have been installed and successfully producing oil since 2005. The results of the nonlinear finite element program ABAQUS used to analyze the Holstein top tensioned risers were evaluated according to the API RP 2RD. The same analytical results are used for evaluating the impact of the proposed ISO 13628-12 in the area of stress evaluation.

Dynamical Model Updating Based on Gradient Regularization Method

2013 ◽  
Vol 351-352 ◽  
pp. 118-121
Author(s):  
He Long Xu ◽  
Jun Xiao ◽  
Yu Xin Zhang
Keyword(s):  
Regularization Method ◽  
Solution Method ◽  
Model Updating ◽  
Input Parameter ◽  
Mode Shapes ◽  
Problem Solution ◽  
Finite Element Program ◽  
Element Program ◽  
Important Input ◽  
The Mathematical Model

Modulus of elasticity is an important input parameter in all kinds of structural analyses. The mathematical model used to identify the structural elastic modulus with measured Frequencies and mode shapes at several points is thusly built up in this paper, and then Gradient-Regularization method, an inverse problem solution method, is employed to solve the problem. General finite element program is compiled, and numerical examples have proved that the method of this thesis is efficient. The issues such as the choice of model error and the choice of measuring points are discussed as well.

Some Aspects of Spar Platform Buoyancy Can Loads

2002 ◽  
Author(s):  
Hugh Thompson ◽  
Mehemosh B. Irani ◽  
Lyle D. Finn
Keyword(s):  
Finite Element ◽  
Field Measurements ◽  
Element Model ◽  
Scale Model ◽  
Spar Platform ◽  
Finite Element Program ◽  
Numerical Predictions ◽  
Element Program ◽  
Actual Field ◽  
The Time Domain

A finite element program is developed to analyze the dynamics of buoyancy cans within the centerwell of Spar platforms. The time domain non-linear finite element model includes the effects of the hydrodynamics of the water within the centerwell, and, the gap between the buoyancy cans and guides. The forces on the buoyancy can guide structure due to Spar motions is studied in the present paper. The theoretical results are validated with experimental and field measurements. 1:20.89 scale model tests are conducted to measure the buoyancy can motions and guide reaction forces for a range of gap sizes and specified Spar motions. A Spar platform is also instrumented to measure the guide forces in actual field conditions. The prototype field data is analyzed and compared with the numerical predictions.

Design Challenges of Top Tensioned Risers in Ultra Deepwater Applications

2011 ◽  
Author(s):  
Yongming Cheng ◽  
Lixin Xu ◽  
Paul Stanton
Keyword(s):  
Production Systems ◽  
Direct Access ◽  
Floating Platform ◽  
Stick Slip ◽  
Capacity Limit ◽  
Global Performance ◽  
Riser Design ◽  
Vessel Motion ◽  
High Payload ◽  
Design Challenges

A Top Tensioned Riser (TTR) system provides direct access to subsea wells from a floating platform for drilling, workover, and completion operations. TTRs have been widely used with floating production systems such as Spars and TLPs in deepwater field developments. This paper investigates design challenges of TTRs in ultra deepwater applications. As application moves to ultra deepwater, challenges of TTRs increase in terms of riser design, analysis, installation and global performance. This paper first introduces a typical TTR configuration in ultra deepwater applications. The TTR design issues cover riser wall thickness which is especially driven by extreme high pressure and high temperature, tension limits, high payload, and long tensioner stroke. The installation concerns come from hook capacity limit, riser Vortex-Induced Vibration (VIV) when the riser is disconnected, and riser bottom drift caused by vessel motion during installation. This paper further investigates the coupling between the risers and floating platform, the interference between riser pairs, riser VIV, and tensioner stick-slip phenomenon. Examples are given to illustrate various aspects of TTRs in ultra deepwater applications. In addition, this paper also explores likely solutions to TTR design challenges.

Water Hammer Response of Flexible Piping by Component Synthesis

1991 ◽  
Vol 113 (1) ◽  
pp. 115-119 ◽  
Author(s):  
F. J. Hatfield ◽  
D. C. Wiggert
Keyword(s):  
Finite Element ◽  
Dynamic Pressure ◽  
Equations Of Motion ◽  
Computer Code ◽  
Water Hammer ◽  
Mode Shapes ◽  
Finite Element Program ◽  
Coupled Equations ◽  
Alternative Approach ◽  
Element Program

Water hammer pressure in piping is modified by the consequent motion of the piping. In general, accurate estimates of dynamic pressure and pipe displacement must account for this interaction. One approach is to formulate and solve the coupled equations of motion for the liquid and pipe structure. Implementation for practical pipe systems would require a computer code comparable in scope to a structural finite element program combined with a hydrodynamics program. This paper presents an alternative approach that utilizes any available finite element program to compute natural frequencies and mode shapes of the piping, and then uses those modes to modify a hydrodynamic analysis and to predict motion of the piping. An example analysis demonstrates application of the method to assess the consequence of removing a brace intended to restrain pipe motion caused by water hammer. Results are compared to those given by analyses that neglect the effect of pipe motion on pressure.

Friction Force and Stresses Analysis for Contact of Assembled Details

2006 ◽  
Vol 113 ◽  
pp. 334-338
Author(s):  
Z. Dreija ◽  
O. Liniņš ◽  
Fr. Sudnieks ◽  
N. Mozga
Keyword(s):  
Mechanical Properties ◽  
Surface Roughness ◽  
Plastic Deformation ◽  
Friction Force ◽  
Sliding Friction ◽  
Friction Model ◽  
Contact Interface ◽  
Finite Element Program ◽  
Elastic Plastic ◽  
Element Program

The present work deals with the computation of surface stresses and deformation in the presence of friction. The evaluation of the elastic-plastic contact is analyzed revealing three distinct stages that range from fully elastic through elastic-plastic to fully plastic contact interface. Several factors of sliding friction model are discussed: surface roughness, mechanical properties and contact load and areas that have strong effect on the friction force. The critical interference that marks the transition from elastic to elastic- plastic and plastic deformation is found out and its connection with plasticity index. A finite element program for determination contact analysis of the assembled details and due to details of deformation that arose a normal and tangencial stress is used.

scholarly journals The impact of drilling and slitting construction on damage field: evolution characteristics in low-permeability coal seam

2021 ◽  
Vol 37 ◽  
pp. 205-215
Author(s):  
Heng Chen ◽  
Hongmei Cheng ◽  
Aibin Xu ◽  
Yi Xue ◽  
Weihong Peng
Keyword(s):  
Finite Element ◽  
Rock Mass ◽  
Damage Mechanics ◽  
Effective Strain ◽  
Secondary Development ◽  
Distribution Area ◽  
Finite Element Program ◽  
Element Program ◽  
Mining Face ◽  
The Impact

ABSTRACT The fracture field of coal and rock mass is the main channel for gas migration and accumulation. Exploring the evolution law of fracture field of coal and rock mass under the condition of drilling and slitting construction has important theoretical significance for guiding efficient gas drainage. The generation and evolution process of coal and rock fissures is also the development and accumulation process of its damage. Therefore, based on damage mechanics and finite element theory, the mathematical model is established. The damage variable of coal mass is defined by effective strain, the elastoplastic damage constitutive equation is established and the secondary development of finite element program is completed by FORTRAN language. Using this program, the numerical simulation of drilling and slitting construction of the 15-14120 mining face of Pingdingshan No. 8 Mine is carried out, and the effects of different single borehole diameters, different kerf widths and different kerf heights on the distribution area of surrounding coal fracture field and the degree of damage are studied quantitatively. These provide a theoretical basis for the reasonable determination of the slitting and drilling arrangement parameters at the engineering site.

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