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TCP is a strong, noncorrosive, spoolable, lightweight technology which is delivered in long lengths, resulting in a reduction of transportation and installation costs. TCP is installed using small vessels or subsea pallets, significantly reducing CO2 emissions. It is also 100% recyclable. Strohm secured a contract with Total and ExxonMobil for a qualification-testing program for a high-pressure, high-temperature (HP/HT) thermoplastic composite pipe (TCP). The qualification project will create a foundation for further development of this TCP technology for riser applications.
Kwon, Yong-Ju (Korea Research Institute of Ships and Ocean Engineering (KRISO)) | Jung, Dongho (Korea Research Institute of Ships and Ocean Engineering (KRISO)) | Park, Byeongwon (Korea Research Institute of Ships and Ocean Engineering (KRISO)) | Jung, Jae-Hawn (Korea Research Institute of Ships and Ocean Engineering (KRISO)) | Oh, Seunghoon (Korea Research Institute of Ships and Ocean Engineering (KRISO))
A series of model tests were performed to investigate the response characteristics of a free hanging riser under forced oscillation conditions. The boundary conditions were considered to be fixed/free (fixed at the top and free at the bottom). The top end of the riser was fixed to the forced oscillator to give the effects of horizontal vessel motion. The model test was performed at the Ocean Engineering Basin of the Korea Research Institute of Ships and Ocean Engineering (KRISO). In this study, the displacements along the riser length were measured using underwater camera systems. Various oscillation conditions were considered in order to investigate the effects of period and amplitude. The oscillation period was determined considering the eigenvalues in the in-line (IL) response. The IL responses of the experiment were compared with the time simulation results of OrcaFlex. The responses of two results had a good agreement on time series, statistical value, and snapshot. The cross-flow (CF) responses along the riser length in the experiment were determined by the Keulegan-Carpenter number at each point of the riser. A comparison result of the IL and CF responses shows that they were excited by different dominant frequencies from the top-end motion and vortex shedding, respectively. While one top-end oscillation frequency appeared in the IL, multi-peak frequencies were investigated at all positions along the riser length in the CF, which is induced by traveling waves.
In this paper we investigate stability for severe slugging including self-lifting by using a stability solver. The stability solver is a tool in which a numerical linear stability analysis is applied to a mathematical model for a two-phase flow in a pipeline-riser system. The self-lifting approach is interesting because different configurations for the stationary state may occur. Depending on the system parameters, experiments show that two unstable regions may exist. Several parametric analyses are realized to evaluate the influence of self-lifting and to determine an optimal operational condition. Stability maps for severe slugging are built, and experimental data from literature are included, showing a very good agreement; in particular, the two unstable regions were satisfactorily predicted by the stability solver.
Hu, Hao (Computational Marine Hydrodynamics Lab (CMHL), State Key Laboratory of Ocean Engineering, School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University) | Deng, Di (Computational Marine Hydrodynamics Lab (CMHL), State Key Laboratory of Ocean Engineering, School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University) | Wan, Decheng (Computational Marine Hydrodynamics Lab (CMHL), State Key Laboratory of Ocean Engineering, School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University)
Vortex-induced vibrations of a vertical tensioned riser under the periodic platform motion, which is simplified as a sinusoidal excitation at riser's top end, are simulated in this paper. The viv-FOAM-SJTU solver is used to build computational fluid dynamics (CFD) model. Three different excitation periods are employed to study the responses of riser. The relative in-line vibration displacement is increased by decreasing the excitation period, and the trajectory shapes are changed with the variation of axial positions and excitation periods of riser. The cross-flow vibrations present multi-modal vibration phenomenon with the reduction of excitation period. The wake field of riser indicates that the washing out of riser by shed vortices contributes to the multi-mode vibrations.
Marine riser is one of the most important parts of the offshore oil and gas exploitation system. Vortex-induced vibrations (VIV) always occurs when the riser is exposed to current. Platform connected at the top of riser generates reciprocating motion with the influence of waves, currents and winds, which produces a relatively oscillatory flow between the water and the riser. The vortex shedding frequencies are changed with the variation of the relatively velocity between riser and current. The resonance phenomenon, called the "lock-in" phenomenon, will happen when the vortex shedding frequency close to natural frequencies of the riser.
Vortex-induced vibrations of marine risers under platform motion have gradually received more attention. A comprehensive mini review of recent investigations have been done by Liu et al (2020).
Park et al (2004). experimentally studied the effect of top-end excitation on transverse vibrations of a hanging riser, and measured in-line and transverse displacements. They found transverse structural wave propagation, which was related with vortex shedding frequency. Senga and Koterayama (2005) experimentally and numerically investigated the vibrations of a flexible riser with irregularly top-end excitation, and developed a new numerical scheme. The numerical results showed good agreement with experimental results except for the long period motion.
Techasirithaworn, Mittrapa (Mubadala Petroleum Thailand) | Tachavarakul, Vichai (Mubadala Petroleum Thailand) | Krittaphol, Nuttawut (Mubadala Petroleum Thailand) | Grassian, David (Mubadala Petroleum)
Aging facilities are a common issue within the oil and gas industry. This research demonstrates a practical approach to aging life extension, taking into account risks and constraints, such as budgets, resources and offshore field-level logistics. The case study reviewed is Mubadala Petroleum's (MPs) small, but aging, upstream offshore oil facility located in the Gulf of Thailand, known as the Jasmine/BanYen field. The field includes six offshore platforms, subsea pipelines and a Floating Production, Storage and Offloading asset (FPSO). The field, which commenced production in 2005, was initially expected to have a relatively short field life, and as a result, the facilities were genially specified for only a 10-year lifespan. As the field exceeded expectations in term of volumes and longevity, it became clear to MP management that a practical and cost effective life extension plan was necessary. As such, this research describes the approach to taken by MP to extend the life of the Jasmine/BanYen facilities.
The approach taken by MP was closely aligned with the recommendations and best practices proposed by several regulatory authorities with extensive experience in managing aging offshore oil and gas facilities, such as the United Kingdom's (UK) Health and Safety Executive (HSE) and the Norwegian Petroleum Safety Authority (PSA). As such, the facilities were first functionally decomposed into a number of subsystems, such as Wells, Structures, Pipelines, Topsides, Risers and Floating Assets. A target life extension period was specified, which was followed by a series of focused risk assessments to determine the levels of risk expected during the life extension period, with the critical gaps identified. Each risk assessment involved specialist resources related to the subsystem under review, such as structural engineers, process engineers, marine engineers, instrument engineers, as well as technical safety and environmental engineers. For any risks that were deemed unacceptable, a mitigation plan was suggested and associated costs developed. Finally, a phased master plan was developed that took into account constraints while prioritizing actions based on the determined risk levels.
The implementation of the plan was challenged by the intricacies of offshore logistics, including constraints on supply boats, Persons On Board (POB) etc., and budgetary constraints, which were considerable given the relatively high operational expenses of the field and the low oil price environment. As per the risk assessment, high priority activities were determined to be with respect to FPSO, well integrity and the integrity of subsea pipelines. The platform structures and topsides were considered to be lower priority, as they had already been verified for the life extension period by the company's Asset Integrity (AI) program. Additionally, MP also has a robust Safety Critical Element (SCE) system in place which is an integral part of the AI program, and as such there were no unexpected revelations with regards to the condition of the SCEs. Obsolescence was determined to be a low priority since the equipment on the platforms are relatively new, and most of the Original Equipment Manufacturers (OEMs) provided assurance on the availability of spare parts for the main equipment items.
Highlights of the life extension plan are as follows: Production flexible riser connecting the steel pipeline network to the FPSO has been replaced Pipelines inspections are ongoing, and repairs are being prioritized The design life of platform subsea structures has been extended based on fatigue analysis Subsidence analysis has been carried out on all platforms and indicated no major anomalies Platform power generation facilities are progressively being upgraded A comprehensive well integrity systems have been implemented and critical activities such as barrier testing and well repairs are being carried out regularly Repairs to the hull of the FPSO have been carried out
Production flexible riser connecting the steel pipeline network to the FPSO has been replaced
Pipelines inspections are ongoing, and repairs are being prioritized
The design life of platform subsea structures has been extended based on fatigue analysis
Subsidence analysis has been carried out on all platforms and indicated no major anomalies
Platform power generation facilities are progressively being upgraded
A comprehensive well integrity systems have been implemented and critical activities such as barrier testing and well repairs are being carried out regularly
Repairs to the hull of the FPSO have been carried out
Abimbola, Fatai Akorede (China University of Petroleum, Beijing) | Yang, Jin (China University of Petroleum, Beijing) | Uche Onuoha, Mac Darlington (China University of Petroleum, Beijing) | Liu, Shujie (CNOOC Research Institute Limited)
An operational technique designed for safe and quick retrieval of deepwater drilling risers during an imminent threat from hurricane or typhoon is developed by proposing a new drilling riser model with disjointed sections for easier and faster disconnection as against the conventional practice of retrieving the whole length of the riser which is tedious, time-consuming and has a huge risk of untimely evacuation of personnel and facilities. A theoretical method is used to model the drilling riser in freestanding disconnected mode and the resulting differential equation is solved numerically. The mechanical behavior of the drilling riser is analyzed for its survivability in freestanding disconnected mode in order to ascertain its useability when the impending typhoon is over. Parametric studies are carried out on key influencing parameters such as buoyancy can upthrust ratio, buoyancy can (BC) position, and riser thickness to arrive at an optimum condition that will ensure the survivability of the drilling riser when disconnected in freestanding mode. Fifteen parametric case studies are presented. In the first five cases, with a varying buoyancy can upthrust ratio but a fixed BC position and riser thickness, it resulted to obtaining a suitable buoyancy can upthrust ratio which is used in subsequent cases. The next six case studies gave a suitable BC position, and finally the last four cases for riser thickness. Results obtained from the fifteen cases are used to get the optimum condition for survivability of the riser in freestanding disconnected mode. A deepwater drilling riser designed in conformity to the optimum configurational conditions as presented in the analysis can survive in the face of an emergency situation such as hurricane or typhoon.
The complete paper discusses the successful application of a data-driven approach to analyze production data and identify root causes of slugging in a subsea production system on the Norwegian Continental Shelf. The approach used machine-learning techniques to model and analyze historical production data to identify the drivers behind slug flow. The results were used in combination with simulator studies and engineering experience to create a better understanding of the underlying root cause and to make it easier for field engineers to leverage all available information to reduce slugging and optimize production. Slugging Challenges in Offshore Fields Subsea production systems, characterized by deep wells and pipeline-riser setups, are especially prone to slug flow. Severe slugging, which can occur in the riser as a result of a pipeline topology-induced low-point angle at the base of the riser, produces only one slug in the riser at a time, and its length can reach that of the entire riser.
Kaldirim, Omer (Texas A&M University) | Kaldirim, Ebubekir (Louisiana State University) | Geresti, Cameron (Texas A&M University) | Manikonda, Kaushik (Texas A&M University) | Schubert, Jerome J. (Texas A&M University) | Hasan, Abu Rashid (Texas A&M University)
Limited studies are available for modeling gas migration in risers. Outdated and small-scale models provide insufficient reliability, and a thorough mechanistic description of the problem is still not available. A significant part of the problem concerns understanding how pressure, temperature, liquid properties, and gas-liquid dynamics effect gas expansion during migration.
This paper provides information on Computational Fluid Dynamics (CFD) simulations performed on gas injections in three static and dynamic vertical fluid columns, with and without back pressure measuring 27-ft. and 330-ft. tall with 6, 12, 19.5 in. diameter. These CFD simulations analyzed the recorded gas expansion, change in pressure and temperature, and the volume fraction of the gas throughout the riser. In addition, these simulations also analyzed the change in flow rate, velocity, and the unloading effect at the inlet and outlet.
The 330-ft. pipe simulation demonstrated explosive unloading behavior with maximum discharge velocity and flow rate of over 2.8-ft./sec. and 6617.5-gpm., while the shorter pipes demonstrated relatively slower overflow. The case with a 330-ft. pipe also recorded a rapid change in temperature close to the top. Back pressure application at the surface minimized the effects of unloading and slowed down expansion.