Over the past 10 years, SINTEF has investigated, or been informed about, a range of torsion failures in cables, umbilicals or flexible pipes. These failures have occurred while the flexible products were being transported along a route during production, loadout, installation. One failure occured during operation. There are no guidelines on how to minimize the risk of such failures. This may be attributed to a lack of knowledge in the industry about the mechanisms that cause torsional moments to appear. Further, some buckling patterns of the components of a flexible product under excessive torsion, closely resemble patterns caused by excessive bending or compressive load, so that some torsion-induced failures are wrongly attributed. Hence, there is a need to increase the knowledge and awareness of torsion failures in the industry. Previous papers by the authors have considered some of the mechanisms that lead to the appearance of torque in handling operations. The present paper is a continuation which focuses on torque-induced failure modes. It begins by providing a systematic nomenclature for the description of torsion kinematics. It then provides a qualitative description of known torque-induced failure modes. The literature provides some models for torque-induced failures, as well as models of component failures due to excessive bending or compression of the flexible product, which are also relevant for the study of torsion. These are reviewed, and their relevance to torsion-induced failures are discussed. Knowledge gaps and challenges are highlighted.
{"title":"Torsion Failures in Handling Operations for Power Cables, Umbilicals and Flexible Pipes","authors":"P. Mainçon, Vegard Longva","doi":"10.1115/omae2021-61503","DOIUrl":"https://doi.org/10.1115/omae2021-61503","url":null,"abstract":"\u0000 Over the past 10 years, SINTEF has investigated, or been informed about, a range of torsion failures in cables, umbilicals or flexible pipes. These failures have occurred while the flexible products were being transported along a route during production, loadout, installation. One failure occured during operation. There are no guidelines on how to minimize the risk of such failures. This may be attributed to a lack of knowledge in the industry about the mechanisms that cause torsional moments to appear. Further, some buckling patterns of the components of a flexible product under excessive torsion, closely resemble patterns caused by excessive bending or compressive load, so that some torsion-induced failures are wrongly attributed. Hence, there is a need to increase the knowledge and awareness of torsion failures in the industry. Previous papers by the authors have considered some of the mechanisms that lead to the appearance of torque in handling operations. The present paper is a continuation which focuses on torque-induced failure modes. It begins by providing a systematic nomenclature for the description of torsion kinematics. It then provides a qualitative description of known torque-induced failure modes. The literature provides some models for torque-induced failures, as well as models of component failures due to excessive bending or compression of the flexible product, which are also relevant for the study of torsion. These are reviewed, and their relevance to torsion-induced failures are discussed. Knowledge gaps and challenges are highlighted.","PeriodicalId":240325,"journal":{"name":"Volume 4: Pipelines, Risers, and Subsea Systems","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131483490","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}
Increasing demand for energy is driving the need to explore the deeper oceans and the far north. While higher temperature, pressure and longer tie-backs are challenges going deep, highly sensitive environment is an issue exploring far north. The discovery of large reserves in the far north has brought the challenges of exploration, production, and transportation in the cold regions like Prudhoe Bay, the Mackenzie Delta, and the Arctic Islands into focus. To transport hydrocarbons to market, pipelines used in the Arctic have unique challenges and stringent design conditions that must be met to ensure reliable operations in such remote and sensitive environments. To avoid flow assurance risks, the adage “the hotter the better” is in stark contrast to the sensitive nature of the Arctic environment to temperature changes, and where “the colder the better” is more appropriate. Permafrost, and its potential disturbance, is the most important factor to be considered for pipeline thermal design. High temperatures can disturb the in-situ state of the permafrost, causing settlement and instability in the permafrost zone. Also, high pipeline temperatures demand deep trenches to avoid melting the surface ice, challenging installation and increasing CAPEX. Designing the pipeline to maintain high internal fluid temperatures to reduce flow assurance risks and lower pipeline outer temperatures to minimize the impact on the environment is the best solution. To maintain high fluid temperatures and reduce heat loss to the environment, the conventional idea of a high value insulation like pipe-in-pipe with a vacuum annulus to avoid heat loss to the sensitive Arctic surroundings may seem to be a good solution, but it may not be the optimal solution. This paper discusses a hypothetical scenario (based on field cases) of a multiphase pipeline design and highlights the associated flow assurance/operational risks.
{"title":"Thermal Design of Pipelines – A Challenge for Flow Assurance in the Arctic","authors":"V. Ponagandla, Liangjian Liu, D. Degeer","doi":"10.1115/omae2021-63069","DOIUrl":"https://doi.org/10.1115/omae2021-63069","url":null,"abstract":"\u0000 Increasing demand for energy is driving the need to explore the deeper oceans and the far north. While higher temperature, pressure and longer tie-backs are challenges going deep, highly sensitive environment is an issue exploring far north. The discovery of large reserves in the far north has brought the challenges of exploration, production, and transportation in the cold regions like Prudhoe Bay, the Mackenzie Delta, and the Arctic Islands into focus. To transport hydrocarbons to market, pipelines used in the Arctic have unique challenges and stringent design conditions that must be met to ensure reliable operations in such remote and sensitive environments.\u0000 To avoid flow assurance risks, the adage “the hotter the better” is in stark contrast to the sensitive nature of the Arctic environment to temperature changes, and where “the colder the better” is more appropriate. Permafrost, and its potential disturbance, is the most important factor to be considered for pipeline thermal design. High temperatures can disturb the in-situ state of the permafrost, causing settlement and instability in the permafrost zone. Also, high pipeline temperatures demand deep trenches to avoid melting the surface ice, challenging installation and increasing CAPEX.\u0000 Designing the pipeline to maintain high internal fluid temperatures to reduce flow assurance risks and lower pipeline outer temperatures to minimize the impact on the environment is the best solution. To maintain high fluid temperatures and reduce heat loss to the environment, the conventional idea of a high value insulation like pipe-in-pipe with a vacuum annulus to avoid heat loss to the sensitive Arctic surroundings may seem to be a good solution, but it may not be the optimal solution. This paper discusses a hypothetical scenario (based on field cases) of a multiphase pipeline design and highlights the associated flow assurance/operational risks.","PeriodicalId":240325,"journal":{"name":"Volume 4: Pipelines, Risers, and Subsea Systems","volume":"61 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126190283","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}
Bruno Luiz Barbosa das Chagas, Celso Kazuyuki Morooka
Advances in subsea exploration in the oceans to discover new petroleum reservoirs and sometimes different kind of minerals at the seabed in ultra deepwater, continuously introduce new challenges in offshore drilling operations. This motivates the development of increasingly safe maritime operations. In offshore petroleum, a marine drilling riser is the pipe that connects a wellhead at the sea bottom to a drillship at the sea surface, as an access to the wellbore. It serves as a guide for the drilling column with the drill bit and conductor to carry cuttings of rock coming from the wellbore drilling and its construction. Drilling riser is constantly exposed to adversity from the environment, such as waves, sea currents and platform motions induced by waves. These elements of the environment are prevailing factors that can cause a riser failure during deepwater drilling operations with undesirable consequences for the environment. In the present work, key parameters that influence the probability of fatigue failure in a marine drilling riser are identified, and a parametric evaluation with those parameters are carried out. Dynamic behavior of a riser is previously calculated and fatigue damage is estimated. Afterwards, the First Order Reliability Method (FORM) is applied to determine the probability of fatigue failure on the riser. Fundamentals of the procedure are described, and results are illustrated through the analysis for a typical riser in deepwater drilling operation. Parametric evaluations are done observing points considered as critical along the riser length, and looking to the sensitivity of key parameters in the process. For this study, the SN curve from API guidelines is applied and accumulated fatigue damage is estimated from simulations of the stress time series and applying the Palmgren-Miner’s rule. Finally, the influence of each parameter in the reliability of fatigue failure is verified and discussions given.
{"title":"A Study on the Main Parameters That Affects the Reliability of Fatigue Failure in a Marine Drilling Riser","authors":"Bruno Luiz Barbosa das Chagas, Celso Kazuyuki Morooka","doi":"10.1115/omae2021-63125","DOIUrl":"https://doi.org/10.1115/omae2021-63125","url":null,"abstract":"\u0000 Advances in subsea exploration in the oceans to discover new petroleum reservoirs and sometimes different kind of minerals at the seabed in ultra deepwater, continuously introduce new challenges in offshore drilling operations. This motivates the development of increasingly safe maritime operations.\u0000 In offshore petroleum, a marine drilling riser is the pipe that connects a wellhead at the sea bottom to a drillship at the sea surface, as an access to the wellbore. It serves as a guide for the drilling column with the drill bit and conductor to carry cuttings of rock coming from the wellbore drilling and its construction. Drilling riser is constantly exposed to adversity from the environment, such as waves, sea currents and platform motions induced by waves. These elements of the environment are prevailing factors that can cause a riser failure during deepwater drilling operations with undesirable consequences for the environment.\u0000 In the present work, key parameters that influence the probability of fatigue failure in a marine drilling riser are identified, and a parametric evaluation with those parameters are carried out. Dynamic behavior of a riser is previously calculated and fatigue damage is estimated. Afterwards, the First Order Reliability Method (FORM) is applied to determine the probability of fatigue failure on the riser. Fundamentals of the procedure are described, and results are illustrated through the analysis for a typical riser in deepwater drilling operation. Parametric evaluations are done observing points considered as critical along the riser length, and looking to the sensitivity of key parameters in the process. For this study, the SN curve from API guidelines is applied and accumulated fatigue damage is estimated from simulations of the stress time series and applying the Palmgren-Miner’s rule. Finally, the influence of each parameter in the reliability of fatigue failure is verified and discussions given.","PeriodicalId":240325,"journal":{"name":"Volume 4: Pipelines, Risers, and Subsea Systems","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131270114","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}
Ragini Gogoi, C. Aubeny, Phillipa Watson, F. Bransby
Suction caissons have emerged as a viable solution for the foundations of offshore wind turbines, which are gaining momentum worldwide as an alternate energy source. When used in a multi-bucket jacket system, the system capacity is often governed by the uplift capacity of the windward bucket foundation. Seabed conditions at offshore windfarm sites often comprise dense sand where the soil response may be drained, partially drained or undrained depending on the loading regime, the foundation dimensions and the soil conditions. Given the large difference in uplift capacity of caissons for these different drainage conditions, predicting the behavior of a suction caisson under a range of drainage conditions becomes a paramount concern. Consequently, this paper presents the findings of a coupled finite element investigation of the monotonic uplift response of the windward caisson of a multi-bucket jacket system in a typical dense silica sand for a range of drainage conditions. The study adopts a Hypoplastic soil constitutive model capable of simulating the stress-strain-strength behavior of dense sand. This choice is justified by conducting a comparative study with other soil models — namely the Mohr Coulomb and bounding surface sand models — to determine the most efficient soil failure model to capture the complex undrained behavior of dense sand. The numerical predictions made in this study are verified by recreating the test conditions adopted in centrifuge tests previously conducted at the University of Western Australia, and demonstrating that the capacity from numerical analysis is consistent with the test results. The Hypoplastic soil constitutive model also provides an efficient method to produce accurate load capacity transition curves from an undrained to a drained soil state.
{"title":"Uplift Capacity of Suction Caissons in Sand for General Conditions Of Drainage","authors":"Ragini Gogoi, C. Aubeny, Phillipa Watson, F. Bransby","doi":"10.1115/omae2021-61663","DOIUrl":"https://doi.org/10.1115/omae2021-61663","url":null,"abstract":"\u0000 Suction caissons have emerged as a viable solution for the foundations of offshore wind turbines, which are gaining momentum worldwide as an alternate energy source. When used in a multi-bucket jacket system, the system capacity is often governed by the uplift capacity of the windward bucket foundation. Seabed conditions at offshore windfarm sites often comprise dense sand where the soil response may be drained, partially drained or undrained depending on the loading regime, the foundation dimensions and the soil conditions. Given the large difference in uplift capacity of caissons for these different drainage conditions, predicting the behavior of a suction caisson under a range of drainage conditions becomes a paramount concern. Consequently, this paper presents the findings of a coupled finite element investigation of the monotonic uplift response of the windward caisson of a multi-bucket jacket system in a typical dense silica sand for a range of drainage conditions. The study adopts a Hypoplastic soil constitutive model capable of simulating the stress-strain-strength behavior of dense sand. This choice is justified by conducting a comparative study with other soil models — namely the Mohr Coulomb and bounding surface sand models — to determine the most efficient soil failure model to capture the complex undrained behavior of dense sand. The numerical predictions made in this study are verified by recreating the test conditions adopted in centrifuge tests previously conducted at the University of Western Australia, and demonstrating that the capacity from numerical analysis is consistent with the test results. The Hypoplastic soil constitutive model also provides an efficient method to produce accurate load capacity transition curves from an undrained to a drained soil state.","PeriodicalId":240325,"journal":{"name":"Volume 4: Pipelines, Risers, and Subsea Systems","volume":"117 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128183646","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}
The simulation and control of the severe slugging flow in the subsea multiphase pipeline is the focus of research in the production and exploitation of oil companies. Severe slug flow results in severe fluctuations of pressure and flow rate at both the wells end and the receiving host processing facilities, causing safety and shutdown risks. To prevent the severe slugging flow regime in multiphase transport pipelines, an Ordinary Differential Equation (ODE) model is established by using the mass conservation law for individual phases in the pipeline and the riser sections. Then, the proposed model is compared to the results from the OLGA simulation. A comparative study of different slugging flow control solutions is conducted. Unscented Kalman Filter (UKF), Wavelet Neural Network (WNN) and UKF&WNN are used for state estimation and combined with PI controller. The UKF and WNN are good nonlinear filters. However, when the nominal choke opening is increased, they work unsatisfying. The UKF&WNN observer shows slightly better results than UKF and WNN when the system has high input disturbance.
{"title":"State Estimation and Slug Control of the Subsea Multiphase Pipeline","authors":"Chao Yu, Chuanxu Wang, Xin Deng, Xueliang Zhang, Haifang Sun, Weiming Peng, Yupeng Liu","doi":"10.1115/omae2021-62392","DOIUrl":"https://doi.org/10.1115/omae2021-62392","url":null,"abstract":"\u0000 The simulation and control of the severe slugging flow in the subsea multiphase pipeline is the focus of research in the production and exploitation of oil companies. Severe slug flow results in severe fluctuations of pressure and flow rate at both the wells end and the receiving host processing facilities, causing safety and shutdown risks. To prevent the severe slugging flow regime in multiphase transport pipelines, an Ordinary Differential Equation (ODE) model is established by using the mass conservation law for individual phases in the pipeline and the riser sections. Then, the proposed model is compared to the results from the OLGA simulation. A comparative study of different slugging flow control solutions is conducted. Unscented Kalman Filter (UKF), Wavelet Neural Network (WNN) and UKF&WNN are used for state estimation and combined with PI controller. The UKF and WNN are good nonlinear filters. However, when the nominal choke opening is increased, they work unsatisfying. The UKF&WNN observer shows slightly better results than UKF and WNN when the system has high input disturbance.","PeriodicalId":240325,"journal":{"name":"Volume 4: Pipelines, Risers, and Subsea Systems","volume":"52 6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129312388","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}
There is increasing demand for subsea transport of well-produced fluids through corrosion resistant pipelines such as stainless steel or bimetallic pipes. The latter are made of carbon steel (CS) pipe and a thin (typically 3.0 mm thick) internal layer of corrosion resistant alloy (CRA) such as 316L, 625, 825 or 904L. The CRA and CS layers are adhered either metallurgically or mechanically by a means of an interference fit. Although less mature than other products, mechanically lined pipes (MLP) are more readily available and economical than both stainless steel or hot-roll bonded (HRB) metallurgically clad pipes. One of the gaps that remains to be filled relates to a reliable assessment method for confirming the MLP integrity during offshore installation and subsea service. The CRA liner in MLP is metallurgically bonded to CS at pipe ends by overlay welding, typically deposited using alloy 625 consumable. At the triple-point interface between the liner, overlay and host pipe, cracks may initiate from fabrication flaws and grow during installation or in service. Therefore, the engineering critical assessment (ECA) should be carried out to evaluate the risk of triple-point cracks breaching the CRA layer at any stage of the pipeline’s life cycle. Currently, no recognised ECA approach exists to allow completing such an assessment. Therefore, a bespoke integrity assessment procedure has been developed and validated both numerically and via laboratory testing. This paper outlines the ECA procedure for triple-point flaws in subsea MLP pipelines, which is undertaken through a combined analytical and numerical calculation and small-scale fracture testing. Fatigue crack growth due to cyclic loading is estimated using a geometry-specific stress intensity factor (SIF) solution derived by finite-element analysis (FEA). Ductile tearing during fracture load events is quantified by small-scale fracture testing on specimens with a representative geometry, designed to match the crack tip constraint of triple-point cracks in MLP.
{"title":"Engineering Critical Assessment of Triple-Point Flaws in Mechanically Lined Pipes","authors":"A. Pépin, T. Tkaczyk, Riadh Abderrazak","doi":"10.1115/omae2021-63450","DOIUrl":"https://doi.org/10.1115/omae2021-63450","url":null,"abstract":"\u0000 There is increasing demand for subsea transport of well-produced fluids through corrosion resistant pipelines such as stainless steel or bimetallic pipes. The latter are made of carbon steel (CS) pipe and a thin (typically 3.0 mm thick) internal layer of corrosion resistant alloy (CRA) such as 316L, 625, 825 or 904L. The CRA and CS layers are adhered either metallurgically or mechanically by a means of an interference fit. Although less mature than other products, mechanically lined pipes (MLP) are more readily available and economical than both stainless steel or hot-roll bonded (HRB) metallurgically clad pipes. One of the gaps that remains to be filled relates to a reliable assessment method for confirming the MLP integrity during offshore installation and subsea service.\u0000 The CRA liner in MLP is metallurgically bonded to CS at pipe ends by overlay welding, typically deposited using alloy 625 consumable. At the triple-point interface between the liner, overlay and host pipe, cracks may initiate from fabrication flaws and grow during installation or in service. Therefore, the engineering critical assessment (ECA) should be carried out to evaluate the risk of triple-point cracks breaching the CRA layer at any stage of the pipeline’s life cycle. Currently, no recognised ECA approach exists to allow completing such an assessment.\u0000 Therefore, a bespoke integrity assessment procedure has been developed and validated both numerically and via laboratory testing. This paper outlines the ECA procedure for triple-point flaws in subsea MLP pipelines, which is undertaken through a combined analytical and numerical calculation and small-scale fracture testing. Fatigue crack growth due to cyclic loading is estimated using a geometry-specific stress intensity factor (SIF) solution derived by finite-element analysis (FEA). Ductile tearing during fracture load events is quantified by small-scale fracture testing on specimens with a representative geometry, designed to match the crack tip constraint of triple-point cracks in MLP.","PeriodicalId":240325,"journal":{"name":"Volume 4: Pipelines, Risers, and Subsea Systems","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127903912","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}
Drilling risers are key components in offshore oil exploration and are present in most of the well construction phases (drilling, casing, cementing and completion). Mobile offshore drilling units can operate in different sites exposed to a range of environmental loadings and water depths. Global riser analyses based on the FE (finite element) method are performed to assess the system feasibility and operating envelopes. In harsh environment and ultradeep water scenarios, the riser running/retrieving operation is one of the most critical due to top-angle limits and riser stress as a result of either contact with the inside of the diverter housing/substructures or loading at the gimbal-spider (API-RP-16Q [1], ISO 13624-1 [2]). The use of beam-column elements is satisfactory for modelling the riser global response, however it may lead to result uncertainty in terms of local response associated with complex geometry, over-stress, stress concentration and contact modelling (DNV-ST-F201 [3], DNVGL-RP-F203 [4], ISO 13628-7 [5]). The objective of this paper is to compare riser analysis results from a global and a local FE analysis. This comparison is used to identify any limitations associated with the use of a global riser analysis approach for determining structural limits for the riser during deployment/retrieving operations. Several recommendations are also provided regarding the use of the global analysis approach.
钻井隔水管是海上石油勘探的关键部件，存在于钻井、套管、固井和完井的大部分施工阶段。移动式海上钻井设备可以在不同的环境载荷和水深下作业。采用有限元法对整体立管进行了分析，以评估系统的可行性和运行包络度。在恶劣的环境和超深水环境中，由于顶角限制和立管应力，隔水管下入/回收作业是最关键的作业之一(API-RP-16Q [1]， ISO 13624-1[2])。梁柱单元的使用对于立管整体响应的建模是令人满意的，然而，它可能导致与复杂几何形状、过度应力、应力集中和接触建模相关的局部响应结果的不确定性(DNV-ST-F201[3]、DNVGL-RP-F203[4]、ISO 13628-7[5])。本文的目的是比较整体有限元分析和局部有限元分析的上升管分析结果。通过这种比较，可以确定在部署/回收作业中，使用全局立管分析方法来确定立管结构限制的任何限制。还就使用全局分析方法提出了若干建议。
{"title":"Comparative Study of Drilling Riser Running/Retrieving Analysis Methodologies","authors":"Leandro Vale, C. Gallagher, M. Souza, D. Carneiro","doi":"10.1115/omae2021-62534","DOIUrl":"https://doi.org/10.1115/omae2021-62534","url":null,"abstract":"\u0000 Drilling risers are key components in offshore oil exploration and are present in most of the well construction phases (drilling, casing, cementing and completion). Mobile offshore drilling units can operate in different sites exposed to a range of environmental loadings and water depths. Global riser analyses based on the FE (finite element) method are performed to assess the system feasibility and operating envelopes. In harsh environment and ultradeep water scenarios, the riser running/retrieving operation is one of the most critical due to top-angle limits and riser stress as a result of either contact with the inside of the diverter housing/substructures or loading at the gimbal-spider (API-RP-16Q [1], ISO 13624-1 [2]).\u0000 The use of beam-column elements is satisfactory for modelling the riser global response, however it may lead to result uncertainty in terms of local response associated with complex geometry, over-stress, stress concentration and contact modelling (DNV-ST-F201 [3], DNVGL-RP-F203 [4], ISO 13628-7 [5]). The objective of this paper is to compare riser analysis results from a global and a local FE analysis. This comparison is used to identify any limitations associated with the use of a global riser analysis approach for determining structural limits for the riser during deployment/retrieving operations. Several recommendations are also provided regarding the use of the global analysis approach.","PeriodicalId":240325,"journal":{"name":"Volume 4: Pipelines, Risers, and Subsea Systems","volume":"56 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134287436","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}
Offloading hoses/flexible pipes are used to transfer compressed natural gas (CNG) from an intermediate floating storage and offloading unit (FSO) to CNG vessel (GASVESSEL). The floating hoses are subjected to environmental loads that are mainly waves, current, and vessel motions from both the FSO and the CNG vessel. Preliminary design of loading/unloading system and dynamic positioning system has been performed. Dynamic analysis of the loading/offloading hose and positioning analysis of the FSO and CNG vessel have been carried out numerically in this study. It is verified that the designed loading/unloading system and positioning system of the two vessels (FSO and CNG vessel) are able to operate safely under the sea-state Hs = 6 m within the defined ESD1 zone.
{"title":"Initial Design and Analysis of a Compressed Natural Gas Transport System","authors":"Decao Yin, H. Ludvigsen, H. Lie, I. Fylling","doi":"10.1115/omae2021-60372","DOIUrl":"https://doi.org/10.1115/omae2021-60372","url":null,"abstract":"\u0000 Offloading hoses/flexible pipes are used to transfer compressed natural gas (CNG) from an intermediate floating storage and offloading unit (FSO) to CNG vessel (GASVESSEL). The floating hoses are subjected to environmental loads that are mainly waves, current, and vessel motions from both the FSO and the CNG vessel.\u0000 Preliminary design of loading/unloading system and dynamic positioning system has been performed. Dynamic analysis of the loading/offloading hose and positioning analysis of the FSO and CNG vessel have been carried out numerically in this study.\u0000 It is verified that the designed loading/unloading system and positioning system of the two vessels (FSO and CNG vessel) are able to operate safely under the sea-state Hs = 6 m within the defined ESD1 zone.","PeriodicalId":240325,"journal":{"name":"Volume 4: Pipelines, Risers, and Subsea Systems","volume":"118 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122302361","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}
The scope of this paper is to provide a method implemented in an application for assessment of dynamic response of free spanning pipelines subjected to combined wave and current loading. The premises for the paper are based on application development within pipeline free span evaluation in a software development project. A brief introduction is provided to the basic hydrodynamic phenomena, principles and parameters for dynamic response of pipeline free spans. The choice of method for static and dynamic span modelling has an influence on calculated modal frequencies and associated stresses. Due to the importance of frequencies and stresses for fatigue and environmental loading calculations, the choice of analysis approach influences the partial safety factor format. The aim of the structural analysis is to provide the necessary input to the calculations of VIV and force model response, and to provide realistic estimations of static loading from functional loads. Environmental flow conditions are implemented in the application, such as steady flow due to current, oscillatory flow due to waves and combined flow due to current and waves. Combined wave and current loading include the long-term current velocity distribution, short-term and long-term description of wave-induced flow velocity amplitude and period of oscillating flow at the pipe level and return period values. Inline and cross-flow vibrations are considered in separate response models. For pipelines and risers, modes are categorized in in-line or cross-flow direction. A force model is also considered for the short-term fatigue damage due to combined current and direct wave actions. Design criteria can be specified for ultimate limit state (ULS) and fatigue limit state (FLS) due to in-line and cross-flow vortex induced vibrations (VIV) and direct wave loading.
{"title":"Implementation of a Method for Free-Spanning Pipeline Analysis","authors":"J. Gullaksen","doi":"10.1115/omae2021-61312","DOIUrl":"https://doi.org/10.1115/omae2021-61312","url":null,"abstract":"\u0000 The scope of this paper is to provide a method implemented in an application for assessment of dynamic response of free spanning pipelines subjected to combined wave and current loading. The premises for the paper are based on application development within pipeline free span evaluation in a software development project. A brief introduction is provided to the basic hydrodynamic phenomena, principles and parameters for dynamic response of pipeline free spans. The choice of method for static and dynamic span modelling has an influence on calculated modal frequencies and associated stresses. Due to the importance of frequencies and stresses for fatigue and environmental loading calculations, the choice of analysis approach influences the partial safety factor format. The aim of the structural analysis is to provide the necessary input to the calculations of VIV and force model response, and to provide realistic estimations of static loading from functional loads. Environmental flow conditions are implemented in the application, such as steady flow due to current, oscillatory flow due to waves and combined flow due to current and waves. Combined wave and current loading include the long-term current velocity distribution, short-term and long-term description of wave-induced flow velocity amplitude and period of oscillating flow at the pipe level and return period values. Inline and cross-flow vibrations are considered in separate response models. For pipelines and risers, modes are categorized in in-line or cross-flow direction. A force model is also considered for the short-term fatigue damage due to combined current and direct wave actions. Design criteria can be specified for ultimate limit state (ULS) and fatigue limit state (FLS) due to in-line and cross-flow vortex induced vibrations (VIV) and direct wave loading.","PeriodicalId":240325,"journal":{"name":"Volume 4: Pipelines, Risers, and Subsea Systems","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115645180","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}
Formentini Federico, Luigi Foschi, Filippo Guidi, Ester Iannucci, Lorenzo Marchionni, Yansa Zulkarnain
This paper is based on the experience made during the design and installation of an offshore pipeline recently completed in Indonesia, where a 24” subsea production pipeline (16km long in 70m water depth) was found susceptible during design to lateral buckling. To limit the development of excessive deformation within the acceptance criteria, a mitigation strategy based on interacting planned buckles has been adopted installing three Buckle Initiators (BI) along the pipeline route. Buckling is a well understood phenomenon. However, this project was characterized by major uncertainties mainly driven by soil characterization, soil-pipe interaction, seabed mobility and soil liquefaction. These uncertainties have played a key role in the in-service buckling design. A lot of engineering efforts have been spent to go through the screening between alternative concepts, the validation of the chosen solution and its detailed engineering phase. This paper discusses the main contributing factors and how the uncertainties have been tackled. The Buckle Initiators are quite large and heavy structures with two main bars: the first ramp has an inclination equal to 30° and the pipeline has been laid on it; a second horizontal ramp was used as sleeper to accommodate the development of the lateral buckle during the operating life. A rotating arm was also used to restrict the pipeline lay corridor on the inclined ramp guaranteeing a combined horizontal and vertical out-of-straightness in the as-laid configuration. The rotating arm has been released as soon as the pipeline passed the BI permitting the pipeline to slide freely over the two BI ramps. The foundation of the Buckle Initiator has a footprint surface of about 60m2 guaranteeing its stability for different soil types characterizing the three installation areas. This more complex solution was preferred with respect to a typical sleeper to increase the robustness of the system in terms of buckle mobilization. The design of the Buckle Initiator was a multidisciplinary activity where many novel concepts were developed and many issues were faced (i.e. pipeline laying on an inclined sleeper, anti-scouring system, foundation design, etc.). The Buckle Initiator design was focused on structural calculations against design loads expected during temporary and operating conditions, geotechnical verifications, installation analysis, pipeline configuration and fatigue assessment. This paper presents all main engineering aspects faced during design and first feedbacks from field after the pipeline installation.
{"title":"Tangguh Project: Multidisciplinary and Challenging Design of a Novel Concept of Buckle Initiator","authors":"Formentini Federico, Luigi Foschi, Filippo Guidi, Ester Iannucci, Lorenzo Marchionni, Yansa Zulkarnain","doi":"10.1115/omae2021-62357","DOIUrl":"https://doi.org/10.1115/omae2021-62357","url":null,"abstract":"\u0000 This paper is based on the experience made during the design and installation of an offshore pipeline recently completed in Indonesia, where a 24” subsea production pipeline (16km long in 70m water depth) was found susceptible during design to lateral buckling. To limit the development of excessive deformation within the acceptance criteria, a mitigation strategy based on interacting planned buckles has been adopted installing three Buckle Initiators (BI) along the pipeline route.\u0000 Buckling is a well understood phenomenon. However, this project was characterized by major uncertainties mainly driven by soil characterization, soil-pipe interaction, seabed mobility and soil liquefaction. These uncertainties have played a key role in the in-service buckling design. A lot of engineering efforts have been spent to go through the screening between alternative concepts, the validation of the chosen solution and its detailed engineering phase. This paper discusses the main contributing factors and how the uncertainties have been tackled.\u0000 The Buckle Initiators are quite large and heavy structures with two main bars: the first ramp has an inclination equal to 30° and the pipeline has been laid on it; a second horizontal ramp was used as sleeper to accommodate the development of the lateral buckle during the operating life. A rotating arm was also used to restrict the pipeline lay corridor on the inclined ramp guaranteeing a combined horizontal and vertical out-of-straightness in the as-laid configuration. The rotating arm has been released as soon as the pipeline passed the BI permitting the pipeline to slide freely over the two BI ramps. The foundation of the Buckle Initiator has a footprint surface of about 60m2 guaranteeing its stability for different soil types characterizing the three installation areas. This more complex solution was preferred with respect to a typical sleeper to increase the robustness of the system in terms of buckle mobilization.\u0000 The design of the Buckle Initiator was a multidisciplinary activity where many novel concepts were developed and many issues were faced (i.e. pipeline laying on an inclined sleeper, anti-scouring system, foundation design, etc.). The Buckle Initiator design was focused on structural calculations against design loads expected during temporary and operating conditions, geotechnical verifications, installation analysis, pipeline configuration and fatigue assessment.\u0000 This paper presents all main engineering aspects faced during design and first feedbacks from field after the pipeline installation.","PeriodicalId":240325,"journal":{"name":"Volume 4: Pipelines, Risers, and Subsea Systems","volume":"144 5","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120930983","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}
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