Volume 5: Pipelines, Risers, and Subsea Systems最新文献

{"title":"Mitigation of Pipeline Free Span Fatigue due to Vortex Induced Vibration Using Longitudinally Grooved Suppression","authors":"K. Jayasinghe, H. Marcollo, A. Potts, Craig Dillon-Gibbons, P. Kurts, P. Pezet","doi":"10.1115/OMAE2018-77716","DOIUrl":"https://doi.org/10.1115/OMAE2018-77716","url":null,"abstract":"Irregular seabed bathymetry around subsea pipelines can lead to the formation of pipeline free spans. When exposed to on-bottom currents these free spans can be subject to Vortex-Induced Vibration (VIV), with consequential effects on the fatigue life of the pipeline. Traditional VIV suppression technologies such as strakes and fairings present installation challenges and durability concerns due to the significant increase in overall diameter associated with the geometric profiles of strakes and fairings.\u0000 Longitudinally Grooved Suppression (LGS) technology was developed from a concept stage through to field deployment on active drilling risers (Johnstone et. al., OMAE 2017) [1]. The low profile and VIV suppression abilities of LGS present an opportunity for a more effective and operationally beneficial VIV suppression solution for pipeline free spans. Based on existing Class guidance for assessing pipeline free spans, a simplified framework for assessing free spans with LGS under a response based approach is presented. The simplified assessment implied a suppression efficiency (reduction in vibration amplitude) of up to 80%. An alternative comparative analysis using a force based approach was also performed in SHEAR7 of a bare pipeline and a LGS-wrapped pipeline. The requirements for qualification of new VIV mitigation technologies are also addressed and an example of an actual field installation of the device is presented, on an existing pipeline free span with low seabed clearance.","PeriodicalId":155568,"journal":{"name":"Volume 5: Pipelines, Risers, and Subsea Systems","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125525863","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An Inverse Problem for Parameter Estimation in a Bend Stiffener System","authors":"Yangye He, M. Vaz, M. Caire","doi":"10.1115/OMAE2018-78180","DOIUrl":"https://doi.org/10.1115/OMAE2018-78180","url":null,"abstract":"The top connection of the flexible pipe attached to the platform supporting structure is considered to be a critical area as it sustains the highest forces and often the maximum curvature in the riser system. Bend stiffener, a polymeric structure with conical shape, is employed to limit the maximum curvature of the riser at the uppermost connection, and protect it against excessive bending and accumulative fatigue damage. In this work, an inverse problem methodology is proposed for estimating unknown parameters in the bend stiffener system, based on a large displacement beam theoretical model combined with the Levenberg-Marquardt Method. The global mathematical formulation is used for nonlinear analysis of the riser/bend stiffener system considering linear elastic symmetric material. A case study is given considering simulated angle measurements in five monitoring positions to estimate two unknown parameters in the system, top tension and polyurethane Young’s modulus. Monte Carlo method is employed to analyze the statistic properties of the estimated parameters with measurement errors. The effects of sensor locations and measurement error ranges on the accuracy of parameter estimation are investigated. It is shown that the proposed procedure can estimate efficiently and accurately unknown parameters in a bend stiffener system. The parameter estimation procedure can also be used to assess other mechanical parameters of the bend stiffener system by angle measurements in certain monitoring positions in realistic production systems.","PeriodicalId":155568,"journal":{"name":"Volume 5: Pipelines, Risers, and Subsea Systems","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123403197","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental Research on Vortex-Induced Vibration of Flexible Catenary Riser Model","authors":"Lin Zhao, Z. Tan, Yucheng Hou, Yanju Yin, Weihao Meng","doi":"10.1115/OMAE2018-78363","DOIUrl":"https://doi.org/10.1115/OMAE2018-78363","url":null,"abstract":"Vortex-induced vibration (VIV) is one of the most important factors accounted for the fatigue damage of long flexible risers in deep water. In this paper, the VIV response characteristics of flexible catenary riser model with the slenderness ratio of 578 were firstly studied by means of scale physical model experiments. In the experiment, the riser model was installed on a towing carriage, which might move horizontally above a wave basin with constant speed to simulate the working condition of the riser model under uniform current. The tension sensor was used to measure the time-history variation of the top tension. The acceleration sensor was used to measure the accelerations of the riser model in cross-flow (CF) and in-line (IL) directions. And the top tension, vibration spectrum, amplitude and vibration locus of the riser were analyzed in accordance with the flexible riser model experiment, and the VIV law of the model experiment working condition was analyzed; then the hydrodynamic software Orcaflex was used to verify the finite element analysis (FEA) of the experiment. The experimental results show that the flexible catenary riser with lower mass ratio and lower bending stiffness has more complex hydrodynamic characteristics than the steel catenary riser (SCR). When the suspension angle remains the same, the top tension of the riser increases with the increase of flow velocity, and the higher the flow velocity, the faster the growth rate; the natural frequency of the riser increases with the increase of flow velocity; the VIV of the riser is the second-order vibration mode when flow velocities range from 0.2m/s to 0.4m/s. The vibration frequencies corresponding to acceleration sensors at different measuring points along the axis of the riser tend to be the same and increase with the increase of flow velocity, which results in “lock-in” near a certain natural frequency close to the vortex shedding frequency. When V = 0.2m/s, the VIV responses of some measuring points of the flexible riser present a positive “8”-shape or oblique “8”-shape vibration, when the amplitude tends to be the maximum. As the flow velocity approaches to 0.8m/s, the “8”-shape vibration disappears and the VIV vibration locus begins to become cluttered, and the variation rate of the VIV phase angle is faster than that at low speeds. The experimental results show that the physical model experimental results is well matched with that of Orcaflex numerical model. The physical model experimental results can reflect the vibration law of flexible risers under actual working conditions and can be used to predict the actual vibration law and characteristics of the VIV of flexible risers.","PeriodicalId":155568,"journal":{"name":"Volume 5: Pipelines, Risers, and Subsea Systems","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128032334","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Modelling Changes to Submarine Pipeline Embedment and Stability due to Pipeline Scour","authors":"S. Draper, T. Griffiths, Liang Cheng, D. White, H. An","doi":"10.1115/OMAE2018-77985","DOIUrl":"https://doi.org/10.1115/OMAE2018-77985","url":null,"abstract":"In this paper a beam bending model is combined with existing predictive formulas for pipeline scour to study changes to pipeline stability during scour and lowering. The model is introduced and demonstrated for a range of simplified conditions, including scour-induced lowering of a pipeline resulting from multiple uniformly spaced scour initiation points. The model is then used with a synthetic seabed generated with a variety of length scales. In this simulation the pipeline is ‘laid’ onto the seabed, leading to the formation of ‘natural’ initiation points for scour. The distribution and spacing of the initiation points (which are a function of the pipeline bending stiffness, tension and seabed roughness) lead to different rates of pipeline lowering and stability. The resulting model may be used within a probabilistic framework to estimate changes to pipeline stability resulting from sediment mobility and scour.","PeriodicalId":155568,"journal":{"name":"Volume 5: Pipelines, Risers, and Subsea Systems","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133307599","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Performance of Pipe-Soil Interaction Models in a Quasi-Dynamic Approach to Pipeline Stability Analysis","authors":"Kourosh Abdolmaleki, J. Gregory","doi":"10.1115/OMAE2018-77988","DOIUrl":"https://doi.org/10.1115/OMAE2018-77988","url":null,"abstract":"This paper presents performance of pipe-soil interaction models in a quasi-dynamic approach to submarine pipeline stability analysis. The quasi-dynamic method, as implemented in the PRCI-OBS software (Level 2), applies a series of most probable maximum waves to the pipe that are derived from extreme value analysis of the given sea state. The theoretical formulation for selecting the most probable maximum waves are derived for further clarity. The PRCI-OBS software (Level 2) was upgraded to allow for this study. The upgrade included addition of the well known Verley and Sotberg model for sand and Verley and Lund model for clay soils to the existing soil models known as PRCI soil models. The upgrade also included fixing previously reported bugs such as over-prediction of embedment in current-dominated cases. The matrix of performance simulations was sufficiently large to allow for making general conclusions. The results confirmed that the discrepancy between old and new soil models increased as the parameters approached extremities of the input matrix. The newly implemented models are based on larger model test data sets and could produce consistent results across the range of input data and thus are recommended.","PeriodicalId":155568,"journal":{"name":"Volume 5: Pipelines, Risers, and Subsea Systems","volume":"51 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123645615","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Large Scale Earthquake Analysis of Integrated Subsea Facilities","authors":"M. Hesar","doi":"10.1115/OMAE2018-78090","DOIUrl":"https://doi.org/10.1115/OMAE2018-78090","url":null,"abstract":"Subsea facilities located in earthquake-prone regions of the world can be subjected to severe excitation and have to be designed in a two-tier manner against both ELE and ALE level earthquakes. The return period of these earthquake levels can be 100–300 years and greater than 1000 years, respectively. These facilities may typically consist of rigid pipelines, sliding PLET structures on skirted or hybrid mudmat foundations, connected via rigid spools or jumpers to manifolds on suction pile foundations, with flexible flowlines hanging off goosenecks.\u0000 In recent practice Subsea 7 have developed a novel methodology for modelling and simulating the seismic response of such complex clusters in which the so called “system effects” are intractable and dominate the response of certain critical components. Chief amongst the latter are rigid spools and jumpers that span large distances between PLEM, PLET and X-Tree structures without touching the seabed.\u0000 In the nonlinear implicit direct integration dynamic FE analyses in Abaqus each of the cluster models in a project is subjected to time history accelerations of seven representative earthquakes, as per ISO 19901-2 requirements. Hysteretic damping characteristics of soil-structure interfaces are modelled with special kinematically hardening elements, calibrated to the site-specific seabed geotechnical properties. Specially developed post processing scripts are used to automatically extract the vital information from the large amount of data produced and perform the unity checks of various components to their respective codes of practice.","PeriodicalId":155568,"journal":{"name":"Volume 5: Pipelines, Risers, and Subsea Systems","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115919628","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Efficient Computation of Irregular Wave Wire Stresses in Flexible Risers","authors":"Gabriel Rombado, N. Cooke, D. Pasala, X. Ni, Andrew Low, A. Majed","doi":"10.1115/OMAE2018-78405","DOIUrl":"https://doi.org/10.1115/OMAE2018-78405","url":null,"abstract":"Accurate computation of tensile armor wire stresses remains a major challenge in flexible riser fatigue life predictions and integrity management. Accuracy of the results relies heavily on capturing the kinematics of the flexible’s helically contra-wound tensile armor layers and their interaction with the other metallic and thermo-plastic layers in a dynamic simulation. The standard industry practice to assess the fatigue life of flexibles is to use high fidelity 3D Finite Element Models (FEMs) to capture the complex kinematics and produce accurate stresses. However, direct simulation of flexible riser detailed FEMs is limited to regular wave analyses and computation of wire stress time-histories subjected to irregular waves have been computationally infeasible. This is due to the complexity of the nonlinear FEM and the long simulation time of the irregular wave environment coupled with large number of fatigue sea states. As a result, simplified approaches which do not directly simulate the local model and instead assume that wire stresses can be interpolated based on static stress versus curvature material curves within a pre-defined tension /pressure envelope have been utilized.\u0000 This paper utilizes Nonlinear Dynamic Substructuring (NDS), a simulation-based approach that that extends the framework of dynamic substructuring to nonlinear problems. NDS enables the efficient nonlinear dynamic simulation of multiple pitch lengths of detailed flexible riser FEM subjected to irregular wave inputs and the computation of wire stress time-histories at any location on the local model.\u0000 In this paper, a 14-inch diameter flexible riser under consideration by ExxonMobil is subjected to vessel motion and wave load in irregular wave environments and is modeled using a detailed 3D FEM and simulated via NDS. The flexible riser design features four tensile armor layers to mitigate localized lateral buckling of the wires near the touch down point. Tension and curvature time-histories of the riser near the hang-off, calculated from a conventional beam model global analysis, is used to drive a 5.1m long local model. Irregular wave wire stress time-histories extracted at the corners of the tensile armor wires are used to compute the fatigue life of the flexible. To demonstrate the inaccuracies associated with the regular wave approach, fatigue life is computed via the regular wave approach and compared against the irregular wave approach. It is shown that the NDS capability to efficiently compute irregular waves mitigates over- and under-predictions due to environment idealizations leading to a more accurate and reliable flexible riser life prediction and structural integrity assessment.","PeriodicalId":155568,"journal":{"name":"Volume 5: Pipelines, Risers, and Subsea Systems","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117277518","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hydrodynamics on Circular Cylinder Close to a Wall: Effects From Wall Boundary Layers","authors":"F. Tong, Liang Cheng, H. An, T. Griffiths","doi":"10.1115/OMAE2018-77518","DOIUrl":"https://doi.org/10.1115/OMAE2018-77518","url":null,"abstract":"We present a study on the hydrodynamics of a circular cylinder close to a wall, which is an idealized representative of subsea pipelines and cables used in both offshore oil and gas and marine renewable energy industries. This research utilizes Computational Fluid Dynamics (CFD) modeling method to investigate the influences of the boundary layer turbulence and the cylinder-to-floor distance on hydrodynamic forces. A significant jump in hydrodynamic forces is observed over the range of Reynolds number that coincides with boundary layer transition from laminar to turbulence. This transition gives rise to a drop in the size of the thickness of the boundary layer at the location of the cylinder. The force jump is also characterised by a pressure increase on the upwind surface of the cylinder, while the pressure decreases on the leeward surface.","PeriodicalId":155568,"journal":{"name":"Volume 5: Pipelines, Risers, and Subsea Systems","volume":"AES-21 2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120999704","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Development of a New Methodology for Riser Deformed Shape Prediction/Monitoring","authors":"Junho Choi, J. H. Kim","doi":"10.1115/OMAE2018-78645","DOIUrl":"https://doi.org/10.1115/OMAE2018-78645","url":null,"abstract":"Ocean environmental conditions, such as waves, winds, and currents, are getting harsher due to climate change. This means that oil and gas production platforms in the ocean may experience unexpectedly large environmental loads bigger than previous design loads. Also, many platforms are reaching the end of their design lives. Ensuring riser integrity is one of the most important issues for platform safety and service-life extension. Currently, monitoring sensors are deployed on risers, and structural evaluation methods are utilized to examine riser integrity. However, there are some limitations to the structural evaluation methods. Furthermore, platform operators continue to seek for more direct and cost-effective riser monitoring method due to the low price of oil. In this study, the MultiSensor Fusion (MSF) system is proposed to surmount technical and economic obstacles in real-time riser-monitoring technology. The MSF system is validated for TLP (tension-leg platform) risers by using numerical sensors and numerical-simulation tools.","PeriodicalId":155568,"journal":{"name":"Volume 5: Pipelines, Risers, and Subsea Systems","volume":"55 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127154880","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Pipeline UHB OOS Design With Variable Pressure and Temperature Distributions","authors":"M. Liu, C. Cross, J. McGrail","doi":"10.1115/OMAE2018-77408","DOIUrl":"https://doi.org/10.1115/OMAE2018-77408","url":null,"abstract":"In this paper, the effect is discussed of both pressure and temperature variations and their bearings on the SRA UHB safety factors. A variable peak distribution characterised by probabilities of distinct design and operating conditions is proposed and developed for performing OOS UHB. A routine has been developed recognizing that such a distribution is generally not available in the SRA software. Bearing in mind that friction is an important parameter in the UHB and OOS analysis but not duly considered in the literature to date, an integrated UHB model is introduced in the SRA to account for axial friction. The probabilistic methodology, its implementation and significance are shown through a series of SRA and parametric studies using Monte Carlo simulations. It is demonstrated that a more sensible UHB SRA can be achieved to minimise unnecessary margins, whereby the design parameters can be represented by appropriate probability density functions taking into consideration of maximum design, operating and surge excursion conditions, system availability and reliability levels. Some conclusions and recommendations are presented on the selection of SRA input parameters.","PeriodicalId":155568,"journal":{"name":"Volume 5: Pipelines, Risers, and Subsea Systems","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127028706","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}