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Mike Campbell - One of the best experts on this subject based on the ideXlab platform.
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Test to Determine Hydrodynamic Interaction Between Drilling Riser, Drill String and Mud
Volume 5B: Pipelines Risers and Subsea Systems, 2017Co-Authors: Songcheng Li, Massimiliano Russo, Mike Campbell, Erling KatlaAbstract:Drilling Riser damping can have a significant effect on the dynamic response of the Drilling system, especially the fatigue response of the wellhead and conductor system. The presence of any Drilling Riser damping helps to diminish the transfer of Riser motions into the wellhead system, which can improve any wellhead fatigue issues.One of the little studied contributors to the system damping is the hydrodynamic damping effect of the interaction between the drill pipe and Drilling fluid inside the Riser. As part of the ongoing Structural Well Integrity Joint Industry Project (JIP), finite element analysis (FEA) with a wide range of drag and inertia coefficients is conducted to simulate the mud drag and inertia on the drill string and the Riser. These sensitivity studies demonstrate that the mud drag and inertia on the drill string could be one of the key driving factors in Riser system damping. To verify the FEA work, the Structural Well Integrity JIP conducted a laboratory test to determine the drag coefficient and added mass coefficient of drill pipe inside a marine Drilling Riser with and without flowing mud and water in the Riser annulus.In this paper, the test setup and the test matrix are introduced, and the methodology for determining drag coefficient and added mass coefficient are explained. The test results are also presented and compared with published test data for open water.Copyright © 2017 by ASME
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maximizing Drilling Riser installation operability for tlp top tensioned Risers
ASME 2013 32nd International Conference on Ocean Offshore and Arctic Engineering, 2013Co-Authors: Mike Campbell, Jim Kaculi, Ryan Koska, Darren MillsAbstract:Top tensioned Risers (TTRs) are a key component in Dry Tree Tension Leg Platform (TLP) systems. TTRs are used for both production and Drilling operations.The operability of the Drilling Riser system can be a key factor in the project economics. In addition to the in-place operability, maximizing the weather windows for running and retrieval of the Drilling Riser system minimizes down time and increases operational flexibility.This paper presents the approach taken to determine Drilling Riser installation envelopes. It discusses the solutions evaluated for increasing Drilling Riser installation envelopes and documents the associated equipment selection and specification.Copyright © 2013 by ASME
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an approach to include observed viv likelihood in Drilling Riser fatigue analyses
ASME 2009 28th International Conference on Ocean Offshore and Arctic Engineering, 2009Co-Authors: Michael Tognarelli, Rene D Gabbai, Mike CampbellAbstract:Field measurements of the response of a number of Drilling Risers indicate that vortex-induced vibration (VIV) occurs significantly less often than predicted by the industry-standard fatigue analysis computer program SHEAR7 V4.4. Several comparisons to model tests and field data, including one published by BP and 2H in 2007 [1], demonstrate that this analysis program is generally quite conservative, given that VIV occurs. Furthermore, this conservatism does not take into account those situations in which VIV fatigue is predicted but none is observed in the field, which adds yet another layer of “hidden” conservatism to design analyses. In an effort to address this and reduce conservatism to a more appropriate level, the probability of occurrence of vortex-induced vibration (VIV) is examined using full-scale measured data. The data has been collected over the past several years from five Drilling Risers without VIV suppression devices. These Risers are on rigs under contract to BP at high-current-susceptible sites worldwide. Collectively, the data correspond to 9,600 10-minute field measurements, equivalent to 0.18 years of continuous monitoring. The Riser response is obtained from motion loggers placed at selected positions along the Riser as described in [1]. Each logger measures 3D accelerations and 2D angular rates. Through-depth currents are measured via Acoustic Doppler Current Profilers (ADCP). By comparison of measurements to computer predictions based on the observed current profile, a relationship is developed between the intensity of the fatigue damage predicted and the probability that VIV is observed in the field. Subsequently, an approach is proposed for scaling analysis predictions to reflect the relative likelihood of VIV. The database of measured and SHEAR7 maximum predicted fatigue damage rates is statistically characterized to determine how it may be used to determine factors of safety (FOS) for VIV design. A worked example for a deepwater Drilling Riser in the GoM is used to show how the FOS methodology can be applied in the case of multiple design currents each with a different annual probability of occurrence.Copyright © 2009 by ASME
Shouwei Zhou - One of the best experts on this subject based on the ideXlab platform.
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Effect of Drilling pipe rotation on vortex induced vibration response of Drilling Riser
Journal of Vibroengineering, 2017Co-Authors: Guorong Wang, Shouwei ZhouAbstract:An experiment was carried out in a basin to investigate rotation of Drilling pipe on vortex induced vibration response of Drilling Riser. Vibration displacement time-history and frequency are obtained. Results show that dominant vibration frequency in the in-line direction is almost twice as high as that in the cross-flow direction. The vibration amplitudes in both the cross-flow and in-line direction increase with an increase in rotation speed of Drilling pipe under the experimental conditions. However, the influence of rotation speed Drilling pipe on Drilling Riser vibration amplitude is insignificant. Dominant frequencies are invariant with variation of Drilling pipe rotation under experimental conditions.
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Experimental study of vortex-induced vibration for Drilling Risers under uniform flow current
Journal of Vibroengineering, 2017Co-Authors: Shouwei Zhou, Zugang LongAbstract:An experiment was conducted in a deep water basin to investigate the vortex-induced vibration mechanism of a Drilling Riser. Various measurements were obtained by the fiber Bragg grating strain sensors, and data was analyzed by modal analysis method. Results show that the vibration mode of the Drilling Riser increases with the increasing flow velocity, and the vibration amplitude in the CF direction is larger than that in the IL direction. The vibrations in the CF and IL directions interact and mutually affect each other. The vibration mode in the IL direction is usually larger than that in the CF direction as the dominant vibration frequency is twice of that in the CF direction. Higher stresses may occur rather in the IL direction than in the CF direction. Hence, fatigue induced by the IL direction should also be taken into consideration when analyzing the fatigue life of a Drilling Riser. The three-time harmonic appears, and the phenomenon becomes more obvious as the flow velocity increased for the effect of the “2T” wake mode under the experiment condition. Displacement trajectories are significantly influenced by dominant vibration frequency and phase angle between the CF and IL directions. Crescent shapes, figure-eight, and inclined figure-eight are appeared in the experiment with the increasing flow velocity.
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deep water Drilling Riser mechanical behavior analysis considering actual Riser string configuration
Journal of Natural Gas Science and Engineering, 2016Co-Authors: Shouwei Zhou, Guorong Wang, Qiang FuAbstract:Abstract A dynamic analysis model considering the actual Riser string configuration is established to analyze the mechanical behavior of a Drilling Riser. The Riser in this model is regarded as a simply supported beam located in the vertical plane and is subjected to axial and lateral ocean environment loadings. The model is solved using the finite element method. The validity of the analysis model has been proved by a similar experiment conducted in a deep water basin and ANSYS. Riser lateral displacement, bending moment, and deflection of the deep water well considering actual Riser string configuration in South China Sea are simulated. The effects of top tension, Drilling platform drift distance, surface current speed, wave height, wave period, wave length, wind speed and damping coefficient on Riser lateral displacement, bending moment, and deflection are also discussed. Results indicate that Riser string configuration has a significant effect on Riser mechanical behavior, particularly in the distribution of bending moment. Riser string configuration designing according to concrete ocean environment can significantly improve the Riser’s mechanical behavior. The distribution of Riser lateral displacement, bending moment, and deflection increases with the increase in surface current speed and Drilling platform drift distance, whereas decreases with the increasing top tension and damping coefficient. The distribution of Riser lateral displacement, bending moment, and deflection significantly increases with the increase in surface current speed and large current speed may lead to large lateral displacement, bending moment, and deflection. Increasing top tension can significantly decrease Riser mechanical behavior parameters and avoid large lateral displacement, bending moment, and deflection when suffering extreme ocean environment conditions in deepwater Drilling field. Drilling platform should avoid a large drift distance, which may result in the deflection over the flex joint working range and the enlargement of the Riser bend moment.
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vortex induced vibration mechanism of Drilling Riser under shear flow
Petroleum Exploration and Development, 2015Co-Authors: Shouwei Zhou, Wei Jiang, Tao PengAbstract:Abstract Vortex-induced vibration of the Drilling Riser under shear flow was studied by experimental method, and the characteristic parameters of vortex-induced vibration under the shear flow were obtained. The vortex-induced vibration response in both in-line and cross-flow directions were captured by measuring technique based on the fiber Bragg grating sensor. The influence of the pre-tension during the experiment was eliminated and the experimental data was analyzed by modal analysis method. Results show that, under the shear flow, the shedding frequencies at different locations are different, however the dominant frequencies of the Drilling Riser at different locations are the same; when the vortex shedding frequency is close to the maximum order of the natural frequency, the lock-in phenomenon occurs, and the dominant frequency equals to this natural frequency; the vortex-induced vibration caused by shear flow is in the form of multi-modal for the influence of modal competition; a single vibration period of the Riser's displacement trajectory appears as an inclined “8” shape, and the multiple vibration period of the Riser's overlapped displacement trajectory appears as a crescent shape in the experimental condition.
Yuanjiang Chang - One of the best experts on this subject based on the ideXlab platform.
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Failure Probability Analysis for Emergency Disconnect of Deepwater Drilling Riser Using Bayesian Network
Bayesian Networks for Reliability Engineering, 2020Co-Authors: Baoping Cai, Zengkai Liu, Yonghong Liu, Yuanjiang Chang, Lei JiangAbstract:Drilling Risers are the crucial connection of subsea wellhead and floating Drilling vessel. Emergency disconnect (ED) is the most important protective measure to secure the Risers and wellhead under extreme conditions. This paper proposes a methodology for failure probability analysis of ED operations using Bayesian network (BN). The risk factors associated with ED operations and the potential consequences of ED failure were investigated. A systematic ED failure and consequence model was established through fault tree and event sequence diagram (FT-ESD) analyses and, then the FT-ESD model was mapped into BN. Critical root causes of ED failure were inferred by probability updating, and the most probable accident evolution paths as well as the most probable consequence evolution paths of ED failure were figured out. Moreover, the probability adaptation was performed at regular intervals to estimate the probabilities of ED failure, and the occurrence probabilities of consequences caused by ED failure. The practical application of the developed model was demonstrated through a case study. The results showed that the probability variations of ED failure and corresponding consequences depended on the states of critical basic events (BEs). Eventually, some active measures in Drilling Riser system design, Drilling operation, ED test, and operation were proposed for mitigating the probability of ED failure.
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A Bayesian Network model for risk analysis of deepwater Drilling Riser fracture failure
Ocean Engineering, 2019Co-Authors: Yuanjiang Chang, Changshuai Zhang, Xiangfei Wu, Jihua Ye, Guoming Chen, Liangbin XuAbstract:Abstract Drilling Risers are crucial connection of subsea wellhead and floating Drilling platform. Fracture failure of deepwater Drilling Risers is the most serious accident in offshore Drilling, which would lead to disastrous consequences. This paper presents a Bayesian Network (BN) model to conduct risk analysis for fracture failure of deepwater Drilling Riser. A Bow-Tie (BT) model is developed to identify the risk factors associated with fracture failure and the potential consequences. Subsequently, evidence theory is used to calculate the prior probability of the input event, and the developed BT model is mapped into BN to carry out risk analysis of fracture failure of Drilling Riser. Finally, the probability updating is implemented using forward reasoning in BN model when new evidence is obtained, and a dynamic risk profile of fracture failure and consequence status are performed using probability adaption of BN with the occurrence of the new identified critical factors over a period of time. The application of the developed model is demonstrated through a case study, and some suggestions drawn from the investigation are presented to further mitigate the risk and the severity of accident consequences of Drilling Riser fracture failure during Drilling operations.
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comprehensive risk assessment of deepwater Drilling Riser using fuzzy petri net model
Process Safety and Environmental Protection, 2018Co-Authors: Yuanjiang Chang, Xiangfei Wu, Jihua Ye, Liangbin Xu, Guoming Chen, Bin Chen, Jianliang ZhouAbstract:Abstract Drilling Risers are the critical connection of subsea wellhead and the floating Drilling unit. With exploration and development of oil and gas resources moving into deepwater, Drilling Riser operations have been characterized with high safety risk and occurrence rate of accidents causing high Drilling downtime and Drilling cost. In the present study, a Fuzzy Petri Net (FPN) methodology is proposed to evaluate the comprehensive risk of deepwater Drilling Risers. A risk index evaluation system was established based on analyses of Drilling Riser accidents and identification of risk factors, and the AHP-EM method was used to determine the weights of them. A 9-tuple set was defined to model Drilling Riser risks according to the FPN theories, and by using the fuzzy reasoning algorithm, risk values of risk factors at different levels and the integrated system were gained by iteration of state matrix. A specific case study of deepwater Drilling Risers of NANHAI-8 Drilling unit in Liuhua oilfield in South China Sea is presented to illustrate the application of proposed approach, and some suggestions drawn from the investigation are presented to further mitigate the risk of Drilling Riser operations. The case study showed that FPN is a practical and reliable method in comprehensive risk evaluation of deepwater Drilling Riser system.
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Analysis on the Operation Fatigue of Deepwater Drilling Riser System
The Open Petroleum Engineering Journal, 2016Co-Authors: Guoming Chen, Jingjie Fu, Jingqi Ji, Qiang Song, Yuanjiang ChangAbstract:Fatigue is one of main failure modes of deepwater Drilling Riser system. Analysis models of wave induced fatigue and vortex induced fatigue of deepwater Drilling Riser are established according to the Riser connection, installation and hang-off operations. Characteristics of wave induced fatigue and vortex induced fatigue of Riser system in different operation modes are studied. The influence of each operation fatigue on the combined fatigue is also identified. The results show that wave induced fatigue damage and vortex induced fatigue damage of upper Riser are large in installation and hard hang-off modes. The fatigue damage of Riser system in soft hang-off mode is less than that in hard hang-off mode. The combined fatigue damage of the upper and lower Riser is large. The lower Riser is under the influence of wave induced fatigue and vortex induced fatigue, while the upper Riser is mainly under the influence of wave induced fatigue, especially that in installation and hang-off modes. The fatigue damages of Riser in installation and hang-off modes have a great influence on the combined fatigue of Riser and cannot be neglected in Riser fatigue analysis.
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analyses and countermeasures of deepwater Drilling Riser grounding accidents under typhoon conditions
Petroleum Exploration and Development, 2013Co-Authors: Guoming Chen, Yuanjiang Chang, Lei Zhang, X U LiangbinAbstract:Abstract For deepwater Drilling Riser system facing grounding risk in the South China Sea, a mechanical analysis model of deepwater Drilling Riser grounding accident was established. Focusing on Drilling Riser grounding accidents of a deepwater floating Drilling platform in the South China Sea, mechanical characteristics and grounding accidents of Riser were analyzed. And the Riser retrieving window was determined. The results showed that the shape of the Riser system after Riser grounding is catenary. The maximums of bending moment and von Mises stress are located at lower flex joint. Platform moon pool, tensioner and lower flex joint are damaged due to severe bending deformation in the upper and lower Drilling Riser system after Riser grounding accidents. The Riser may fracture if Drilling platform continues to move toward shallow water. Drilling platform displacement and Riser lift height must be within the Riser operation window during Riser retrieving, or else the Riser may fracture and the LMRP may suffer further damage. Residual Riser and LMRP can be retrieved in a fixed position when the Drilling Riser system is separated from seabed.
Massimiliano Russo - One of the best experts on this subject based on the ideXlab platform.
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Drilling Riser Model Test for Software Verification
Journal of Offshore Mechanics and Arctic Engineering-transactions of The Asme, 2017Co-Authors: Massimiliano Russo, Guttorm GrytøyrAbstract:Marine Drilling Riser is subject to complicated environmental loads which include top motions due to mobile offshore Drilling unit (MODU), wave loads, and current loads. Cyclic dynamic loads will cause severe fatigue accumulation along the Drilling Riser system, especially at the subsea wellhead (WH). Statoil and BP have carried out a comprehensive model test program on Drilling Riser in MARINTEK's Towing Tank in February 2015. The objective is to validate and verify software predictions of Drilling Riser behavior under various environmental conditions by the use of model test data. Six Drilling Riser configurations were tested, including different components such as upper flex joint (UFJ), tensioner, marine Riser, lower marine Riser package (LMRP), blow-out preventer (BOP), lower flex joint (LFJ), buoyancy elements, and seabed boundary model. The Drilling Riser models were tested in different load conditions. Measurements were made of microbending strains and accelerations along the Riser in both in-line (IL) and crossflow (CF) directions. Video recordings were made both above and under water. In this paper, the test setup and test program are presented. Comparisons of results between model test and RIFLEX simulation are presented on selected cases. Preliminary results show that the Drilling Riser model tests are able to capture the typical dynamic responses observed from field measurement, and the comparison between model test and RIFLEX simulation is promising.
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Test to Determine Hydrodynamic Interaction Between Drilling Riser, Drill String and Mud
Volume 5B: Pipelines Risers and Subsea Systems, 2017Co-Authors: Songcheng Li, Massimiliano Russo, Mike Campbell, Erling KatlaAbstract:Drilling Riser damping can have a significant effect on the dynamic response of the Drilling system, especially the fatigue response of the wellhead and conductor system. The presence of any Drilling Riser damping helps to diminish the transfer of Riser motions into the wellhead system, which can improve any wellhead fatigue issues.One of the little studied contributors to the system damping is the hydrodynamic damping effect of the interaction between the drill pipe and Drilling fluid inside the Riser. As part of the ongoing Structural Well Integrity Joint Industry Project (JIP), finite element analysis (FEA) with a wide range of drag and inertia coefficients is conducted to simulate the mud drag and inertia on the drill string and the Riser. These sensitivity studies demonstrate that the mud drag and inertia on the drill string could be one of the key driving factors in Riser system damping. To verify the FEA work, the Structural Well Integrity JIP conducted a laboratory test to determine the drag coefficient and added mass coefficient of drill pipe inside a marine Drilling Riser with and without flowing mud and water in the Riser annulus.In this paper, the test setup and the test matrix are introduced, and the methodology for determining drag coefficient and added mass coefficient are explained. The test results are also presented and compared with published test data for open water.Copyright © 2017 by ASME
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Drilling Riser Model Tests for Software Verification
Volume 2: CFD and VIV, 2016Co-Authors: Massimiliano Russo, Guttorm GrytøyrAbstract:Marine Drilling Riser is subject to complicated environmental loads which include top motions due to Mobile Offshore Drilling Unit (MODU), wave loads and current loads. Cyclic dynamic loads will cause severe fatigue accumulation along the Drilling Riser system, especially at the subsea well head (WH).Statoil and BP have carried out a comprehensive model test program on Drilling Riser in MARINTEK’s Towing Tank in February 2015. The objective is to validate and verify software predictions of Drilling Riser behaviour under various environmental conditions by use of model test data.Six Drilling Riser configurations were tested, including different components such as Upper Flex Joint (UFJ), tensioner, marine Riser, Lower Marine Riser Package (LMRP), Blow-Out Preventer (BOP), Lower Flex Joint (LFJ), buoyancy elements and seabed boundary model.The Drilling Riser models were tested in different load conditions:1. Forced top motion tests2. Regular wave test3. Combined regular wave and towing test4. Irregular wave test5. Combined irregular wave and towing test6. Towing test (VIV)Measurements were made of micro bending strains and accelerations along the Riser in both In-Line (IL) and Cross-Flow (CF) directions. Video recordings were made both above and under water.In this paper, the test set-up and test program are presented. Comparisons of results between model test and RIFLEX simulation are presented on selected cases. Preliminary results show that the Drilling Riser model tests are able to capture the typical dynamic responses observed from field measurement, and the comparison between model test and RIFLEX simulation is promising.Copyright © 2016 by ASME
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Drilling Riser viv tests with prototype reynolds numbers
ASME 2013 32nd International Conference on Ocean Offshore and Arctic Engineering, 2013Co-Authors: Henning Braaten, Massimiliano Russo, Jamison Szwalek, Rolf BaarholmAbstract:For deep-water Riser systems, Vortex Induced Vibrations (VIV) may cause significant fatigue damage. It appears that the knowledge gap of this phenomenon is considerable and this has caused a high level of research activity over the last decades. Small scale model tests are often used to investigate VIV behaviour. However, one substantial uncertainty in applying such results is scaling effects, i.e. differences in VIV response in full scale flow and small scale flow. To (partly) overcome this obstacle, a new innovative VIV test rig was designed and built at MARINTEK to test a rigid full scale Riser model. The rigid Riser model is mounted vertically and can either be elastically mounted or be given a forced motion. In the present version, the cylinder can only move in the cross-flow (CF) direction and is restricted in the in-line (IL) direction.The paper reports results from a Drilling Riser VIV experiment where the new rest rig has been used. The overall objective of the work is to study possible VIV suppression to improve operability of retrievable Riser systems with auxiliary lines by adding Riser fins. These fins are normally used as devices for protection of the auxiliary lines.The test program has recently been completed and analysis is an on-going activity. However, some results can be reported at this stage and more results are planned to be published.A bare Riser model was used in a Reynolds number (Rn) scaling effect study. The Riser model was elastically mounted and towed over a reduced velocity range around 4 – 10 in two different Rn ranges, 75 000 – 192 000 (subcritical regime) and 347 000 – 553 000 (critical regime). The difference in the displacement amplitude to diameter ratio, A/D, is found to be significant.The elastically mounted Riser was also towed with various Drilling Riser configurations in order to study VIV/galloping responses. One configuration included a slick joint Riser model with 6 kill & choke lines; another has added Riser fins too. The Riser model is based on a specific Drilling Riser and the kill and choke lines have various diameters and have a non-symmetrical layout.The various Riser configurations have also been used in forced motion tests where the towed model has been given a sinusoidal CF motion. Forces have been measured. Determination of the force coefficients is still in progress and is planned to be reported later.Scaling effects appear to be a significant uncertainty and further research on the subject is recommended.The slick joint Drilling Riser configuration generally increased the displacements compared to displacements of the bare Riser model. The Drilling Riser configuration with protection fins, kill and choke lines generally reduced the displacements compared to displacements of the bare Riser model. For both Riser systems, tests showed that the response is sensitive to the heading of the current.Copyright © 2013 by ASME
Liangbin Xu - One of the best experts on this subject based on the ideXlab platform.
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Numerical Solutions and Model Test Design for Anti-Typhoon Drilling Riser
Volume 1: Offshore Technology; Offshore Geotechnics, 2019Co-Authors: Jinlong Wang, Liangbin Xu, Lihui Li, Hui Zhang, Leixiang ShengAbstract:Abstract Anti-typhoon Drilling Riser, a solution to overcome high time cost of offshore Drilling Riser emergency retrieval under the situation of imminent arrival of a typhoon, is to modify the existing Drilling Riser to make it disconnectable closer to the surface and leave the long Riser string below (and subsea blowout preventer (BOP)) in a safe and freestanding mode to survive the typhoon. The freestanding Riser is held up by a buoyancy can system. And during the normal Drilling operation, the buoyancy can maintain neutral thus it has limited effect on the Riser overall global performance. However, locally the buoyancy can system will have some effect on the Riser system nearby. To study these effects, numerical analytical methodology and results of anti-typhoon Drilling rise under connected mode and freestanding mode are proposed, and a model test of 1:21 scale factor is designed. Three configuration modes: freestanding mode, connected mode and disconnecting mode are simulated in the tank test. A series of load cases under various current and wave, buoyancy upthrust are conducted in the experimental test to evaluate the hydrodynamic and strength performance of the Riser near buoyancy can. The numerical solution and model test design can be a significant basis of water tank test for anti-typhoon Drilling Riser and a valuable reference for deepwater Drilling engineering.
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A Bayesian Network model for risk analysis of deepwater Drilling Riser fracture failure
Ocean Engineering, 2019Co-Authors: Yuanjiang Chang, Changshuai Zhang, Xiangfei Wu, Jihua Ye, Guoming Chen, Liangbin XuAbstract:Abstract Drilling Risers are crucial connection of subsea wellhead and floating Drilling platform. Fracture failure of deepwater Drilling Risers is the most serious accident in offshore Drilling, which would lead to disastrous consequences. This paper presents a Bayesian Network (BN) model to conduct risk analysis for fracture failure of deepwater Drilling Riser. A Bow-Tie (BT) model is developed to identify the risk factors associated with fracture failure and the potential consequences. Subsequently, evidence theory is used to calculate the prior probability of the input event, and the developed BT model is mapped into BN to carry out risk analysis of fracture failure of Drilling Riser. Finally, the probability updating is implemented using forward reasoning in BN model when new evidence is obtained, and a dynamic risk profile of fracture failure and consequence status are performed using probability adaption of BN with the occurrence of the new identified critical factors over a period of time. The application of the developed model is demonstrated through a case study, and some suggestions drawn from the investigation are presented to further mitigate the risk and the severity of accident consequences of Drilling Riser fracture failure during Drilling operations.
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comprehensive risk assessment of deepwater Drilling Riser using fuzzy petri net model
Process Safety and Environmental Protection, 2018Co-Authors: Yuanjiang Chang, Xiangfei Wu, Jihua Ye, Liangbin Xu, Guoming Chen, Bin Chen, Jianliang ZhouAbstract:Abstract Drilling Risers are the critical connection of subsea wellhead and the floating Drilling unit. With exploration and development of oil and gas resources moving into deepwater, Drilling Riser operations have been characterized with high safety risk and occurrence rate of accidents causing high Drilling downtime and Drilling cost. In the present study, a Fuzzy Petri Net (FPN) methodology is proposed to evaluate the comprehensive risk of deepwater Drilling Risers. A risk index evaluation system was established based on analyses of Drilling Riser accidents and identification of risk factors, and the AHP-EM method was used to determine the weights of them. A 9-tuple set was defined to model Drilling Riser risks according to the FPN theories, and by using the fuzzy reasoning algorithm, risk values of risk factors at different levels and the integrated system were gained by iteration of state matrix. A specific case study of deepwater Drilling Risers of NANHAI-8 Drilling unit in Liuhua oilfield in South China Sea is presented to illustrate the application of proposed approach, and some suggestions drawn from the investigation are presented to further mitigate the risk of Drilling Riser operations. The case study showed that FPN is a practical and reliable method in comprehensive risk evaluation of deepwater Drilling Riser system.
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dynamic analysis of a hang off Drilling Riser considering internal solitary wave and vessel motion
Journal of Natural Gas Science and Engineering, 2017Co-Authors: Chaowei Li, Liangbin Xu, Zhiming Wang, Yu Wang, Xu FengAbstract:Abstract Hang-off mode of a Drilling Riser is occasionally needed during subsea installation/platform relocation operations or evacuation after an emergency disconnection. A suspending Riser without any restriction at its bottom is more flexible and more dangerous in complex sea states than a connected Riser with excess axial tension. Internal solitary waves (ISWs) can particularly exert a sudden impact and shearing force on Risers, and vessel motion can expand horizontal dynamic responses of the Risers. In this paper, considering vessel motion and the combined excitation of ocean currents, surface waves and ISWs, a dynamic model is constructed based on the Euler-Bernoulli theory, in which ISW is simulated by the Korteweg-de Vries (KdV) equation with a two-layer seawater model. Then, the structural governing equation is numerically solved by the Wilson- θ method and preconditioned generalized minimal residual method (GMRES) with a self-developed MATLAB program. Case calculation shows that ISW can largely increase the envelopes of Riser properties in the upper seawater layer and dramatically expand the horizontal deviation of the bottom of a hang-off Riser during ISW spreading. Particularly, the dynamic responses of a Riser will be larger with ISW amplitude augmentation, and larger with an increase in the density difference between the two seawater layers. In addition, vessel motion can increase the horizontal deviation along the entire length of a Riser with a range that is nearly the same as that of the vessel motion amplitude, and increase the envelopes of bending moment and shearing force at the lower section of the Riser near the Riser bottom. Therefore, limiting the vessel motion amplitude, optimizing the vessel towing speed, maintaining a lower marine Riser package (LMRP) at the Riser bottom to strengthen axial tension, and using slick joints with larger wall thicknesses in the upper depth may be effective engineering considerations. More importantly, much attention should be paid to avoid the Riser bottom/LMRP striking other subsea equipment in oceans in which ISWs occur frequently.
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flow and flow control modeling for a Drilling Riser system with auxiliary lines
Ocean Engineering, 2016Co-Authors: Wenbo Wu, Liangbin Xu, Jiasong Wang, Shiquan Jiang, Leixiang ShengAbstract:In this numerical study, it was mainly intended to investigate the flow and flow control for a practical Drilling Riser system with auxiliary lines at various incidence angles. The flow past the Riser system was simulated through solving the Reynolds averaged Navier–Stokes equations and k−ω turbulence model. The cases about fluid flow past single cylinder, two staggered cylinders and eight even-distributed auxiliary lines around main line were simulated first, and the results match well with previous researches. The Reynolds number (Re) used here was 35,000, which belongs to the subcritical Reynolds region, and the flow in this Reynolds region can shows the typical flow characteristics in practical Drilling operator. The effects of the incidence angle, which was in the range of 0–360° and at 30° intervals, on the drag and lift coefficients, the pressure distribution around the main line, the vortex shedding frequencies and the flow structure were investigated. The mean and RMS values of the drag and lift coefficients of the main line vary with the incidence angle irregularly due to the complexity of the geometry of the Riser system. The flow patterns can be classified into six types based on the time-averaged streamlines. The effects of the auxiliary lines on mean force coefficients of the main line in different flow patterns were discussed in detail based on the distributions of the pressure on the main line. The auxiliary lines can suppress the vortex shedding on the main line at all incidence angles. Especially, in the CVP (clamped vortices pair, α=210° and α=330°) pattern, the vortex shedding behind the main line is suppressed most effectively by multiple downstream auxiliary lines. The mean value of the drag coefficient is just about 45.5% of that of the single cylinder, and the RMS value of the lift coefficient is about 1.5% of that of the single cylinder. This is the favorable condition for Drilling operation. The worst effect of suppression occurs in the SLA (shear layers afflux, α=90°) pattern, and the RMS value of the lift coefficient is about 76.8% of that of the single cylinder. Due to the interaction between the vortices shed from different lines in Riser system, the frequencies of the lift coefficients of the lines in Riser system change largely, and some higher frequencies appear in the lift coefficients of the main line. As α=60° and α=120°, the Strouhal number of the main line is about 0.75.
