Reliability Study of a North-Sea Jack-Up Under Action of Wave-in-Deck, SH- and SV-Seismic Waves Considering Spud-Can-Soil Interaction

2010 ◽  
Author(s):  
M. Reza Emami Azadi
Keyword(s):  
North Sea ◽  
Seismic Waves ◽  
Soil Parameters ◽  
Wave Load ◽  
Load Modeling ◽  
Annual Probability ◽  
Plate Elements ◽  
Hyper Elastic ◽  
Interaction Modeling ◽  
Jack Up

In the current study, the effect of spud-can-soil interaction modeling as well as wave load modeling and sea-state on the reliability index of a three-leg North-sea drilling type jack-up platform is studied. The platform has operated in depths of 95–105m and its three main legs modeled as pipe elements and the main deck is also modeled using general beam and also shell/plate elements. The spud-can foundation is modeled using elasto-plastic, hyper-elastic springs as well as spud-model of usfos using a general non-associative plasticity model. The wave-in-deck load is considered using API-RP2A [1], Shell and Statoil models. The SH and SV-seismic waves are considered separately at spud-can base as scaled. The preliminary results of this study showed that the annual probability of failure for the Jack-up platform is significantly affected by the random-sea and wave-in-deck modeling as well as spud-can-soil interaction modeling and soil parameters. Study of importance factors indicated that more refined spud-can-soil interaction modeling as well as wave-in-deck load modeling might improve the calculation models and hence reduce their associated uncertainty in reliability analysis of jack-up type platform.

Influence of Spud-Can-Soil Interaction Modeling and Parameters on the Reliability Index of Neka Drilling Jack-Up Platform

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
M. R. Emami Azadi
Keyword(s):  
Reliability Index ◽  
Clayey Soil ◽  
Interaction Model ◽  
Soil Parameters ◽  
The Caspian Sea ◽  
Foundation Soil ◽  
Soil System ◽  
Dense Sand ◽  
Interaction Modeling ◽  
Jack Up

In the present study, the influence of spud-can-soil modeling and parameters on the reliability index of jack-up platform is investigated. Neka platform is studied as a case, which is a three-leg drilling jack-up type platform located in water depth of about 91 m in the Caspian Sea region. Various spud-can-soil interaction models such as pinned, fixed-base, hyperelastic, and nonlinear elastoplastic spud-can models are applied. The soil type is varied from loose to dense sand and also from soft NC clay to very stiff OC Clay. The effect of bias and coefficient of variation (COV) of the spud-can-soil interaction modeling and also the soil parameters such as the effective interface soil friction angle and also the undrained shear strength of clayey soil are studied. The results showed that inclusion of spud-can-soil interaction may have a considerable effect on the reliability of the jack-up platform. In particular, the bias and COV of soil have shown to have more significant effect on the reliability of jack-up platform in loose sand and soft clayey type soils. It is also found that bias in strength modeling of jack-up itself has less profound effect on the reliability index of the jack-up-foundation-soil system. Importance factors of spud-can-soil modeling are found to be quite considerable. The key aspect is that the inclusion of jack-up-spud-can-soil interaction is more crucial with respect to the reliability of jack-up platform than the choice of interaction model itself.

Influence of Spud-Can-Soil Interaction Modeling and Parameters on the Reliability Index of Neka Drilling Jack-Up Platform

2008 ◽  
Author(s):  
M. R. Emami Azadi
Keyword(s):  
Reliability Index ◽  
Clayey Soil ◽  
Interaction Model ◽  
Friction Angle ◽  
Soil Parameters ◽  
Foundation Soil ◽  
Soil System ◽  
Dense Sand ◽  
Interaction Modeling ◽  
Jack Up

In the present study, the influence of spud-can-soil modeling and parameters on the reliability index of jack-up platform is investigated. Neka platform is studied as a case which is a 3-leg drilling jack-up type platform located in water depth of about 91m in Caspian Sea region. Various spud-can-soil interaction models such as pinned, fixed-base, hyper-elastic and non-linear elasto-plastic spud-can models are applied. The soil type is varied from loose to dense sand and also from soft NC-clay to very stiff OC-Clay. The effects of bias and COV of the spud-can-soil interaction modeling and also the soil parameters such as effective interface soil friction angle and also un-drained shear strength of clayey soil are studied. The results showed that inclusion of spud-can-soil interaction may have a considerable effect on the reliability of the Jack-up platform. In particular, the bias and COV of soil shown to have more significant influence on the reliability of jack-up platform in loose sand and soft clayey type soils. It is also found that bias in strength modeling of jack-up itself has less profound effect on the reliability index of the jack-up-foundation-soil system. Importance factors of spud-can-soil modeling are found to be quite considerable. The key aspect is that the inclusion of jack-up-spud-can-soil interaction is more crucial with respect to the reliability of jack-up platform than the choice of interaction model itself.

scholarly journals An Analytical Procedure to Predict Transverse Vibration Response of Jack-Up Riser under the Random Wave Load

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Fengde Wang ◽  
Wensheng Xiao ◽  
Yanan Yao ◽  
Qi Liu ◽  
Changjiang Li
Keyword(s):  
Dynamic Response ◽  
Oil And Gas ◽  
Beam Theory ◽  
Random Wave ◽  
Wave Load ◽  
Main Component ◽  
Gas Leaks ◽  
Jack Up ◽  
Euler Bernoulli Beam ◽  
Transverse Response

Marine riser is a key equipment in offshore drilling operation, and failure of the riser can lead to drilling moratorium; in severe cases, it may cause oil and gas leaks. In this paper, the time-dependent boundary conditions of the riser and the randomness of wave load are considered to improve the calculation efficiency and accuracy of the dynamic response of the jack-up riser. Based on the Euler–Bernoulli beam theory, an analytical method to determine the response of the jack-up riser subjected to the random wave load was established by the Mindlin–Goodman method in the frequency domain, and an experiment was carried out to verify it. The research shows that transverse dynamic response is the main component of the transverse response of the riser, and the method proposed is feasible to calculate the transverse response of the riser.

System Identification of Jack-Up Platform by Spectral Analysis

2010 ◽  
Author(s):  
X. M. Wang ◽  
C. G. Koh ◽  
T. N. Thanh ◽  
J. Zhang
Keyword(s):  
Spectral Analysis ◽  
System Identification ◽  
Time Domain ◽  
Time History ◽  
Offshore Structures ◽  
Wave Load ◽  
History Of ◽  
Structural Responses ◽  
Jack Up ◽  
Numerical Strategy

For the purpose of structural health monitoring (SHM), it is beneficial to develop a robust and accurate numerical strategy so as to identify key parameters of offshore structures. In this regard, it is difficult to use time-domain methods as the time history of wave load is not available unless output-only methods can be developed. Alternatively, spectral analysis widely used in offshore engineering to predict structural responses due to random wave conditions can be used. Thus the power spectral density (PSD) of structural response may be more appropriate than time history of structural responses in defining the objective (fitness) function for system identification of offshore structures. By minimizing PSD differences between measurements and simulations, the proposed numerical strategy is completely carried out in frequency domain, which can avoid inherent problems rising from random phase angles and unknown initial conditions in time domain. A jack-up platform is studied in the numerical study. A search space reduction method (SSRM) incorporating the use of genetic algorithms (GA) as well as a substructure approach are adopted to improve the accuracy and efficiency of identification. As a result, the stiffness parameters of jack-up legs can be well identified even under fairly noisy conditions.

Wave Load and Structural Analysis for a Jack-Up Platform in Freak Waves

2007 ◽  
Author(s):  
Ould el Moctar ◽  
Thomas E. Schellin ◽  
Milovan Peric
Keyword(s):  
Structural Model ◽  
Stokes Equations ◽  
Nonlinear Effects ◽  
Breaking Waves ◽  
Wave Loads ◽  
Wave Load ◽  
Two Phase ◽  
Freak Waves ◽  
Highly Nonlinear ◽  
Jack Up

The paper analyzed effects of freak waves on a mobile jack-up drilling platform stationed in exposed waters of the North Sea. Under freak wave conditions, highly nonlinear effects, such as wave run-up on platform legs and impact-related wave loads on the hull, had to be considered. Traditional methods based on the Morison formula needed to be critically examined to accurately predict these loads. Our analysis was based on the use of advanced CFD techniques. The code used here solves the Reynolds-averaged Navier-Stokes equations and relies on the interface-capturing technique of the volume-of-fluid type. It computed the two-phase flow of water and air to describe the physics associated with complex free-surface shapes with breaking waves and air trapping, hydrodynamic phenomena that had to be considered to yield reliable predictions. Lastly, the FEM was used to apply the wave-induced loads onto a comprehensive finite element structural model of the platform, yielding deformations and stresses.

scholarly journals Proximate underwater soundscape of a North Sea offshore petroleum exploration jack-up drilling rig in the Dogger Bank

2020 ◽  
Vol 148 (6) ◽  
pp. 3971-3979
Author(s):  
Victoria L. G. Todd ◽  
Laura D. Williamson ◽  
Jian Jiang ◽  
Sophie E Cox ◽  
Ian B. Todd ◽  
...  
Keyword(s):  
North Sea ◽  
Petroleum Exploration ◽  
Dogger Bank ◽  
Drilling Rig ◽  
Jack Up ◽  
Offshore Petroleum
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