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Liu, Yingyi (Research Institute for Applied Mechanics, Kyushu University Kasuga) | Hu, Changhong (Research Institute for Applied Mechanics, Kyushu University Kasuga) | Yoshida, Shigeo (Research Institute for Applied Mechanics, Kyushu University Kasuga)
A time-domain method is developed for modeling the dynamics of a floating truss-structure wind turbine with multiple rotors mounted on the deck of the platform. In its hydrodynamic aspect, a hybrid panel-stick model is built up incorporating the potential flow theory to evaluate the wave inertia force and a Morison strip method to evaluate the wave drag force. The proposed analysis model is validated against a 1/50 scale test of a semi-submersible floating wind turbine, which was carried out in Kyushu University. Good agreement between the simulation results and the experimental data confirms the validity of the developed method. Further numerical simulations are performed in a set of wind and wave conditions to investigate the effect of wave drag force on the dynamics of the floating wind turbine. The results show that applying a hybrid panel-stick model is fairly effective to reduce the unphysical large resonant responses.
Semisubmersible type is one mainstream type of FWTs (floating wind turbines). An important issue of the semisubmersible foundations is to predict their motion responses, among which the heave response may be of a particular concern. At the natural frequencies, when using a potential flow based method, the semisubmersible normally endures remarkable resonant responses. The reason lies in that, near the boundary layer of the submerged part of the floating structure, the waveinduced drag force (which is a viscous force) has not been accounted for as that is usually done in a Navier-Stokes equation based solver. To include the viscous effect, the potential flow based method needs to be modified to some extent. On the other hand, although there have been some good works on determining the wave-induced loads upon a semisubmersible platform (e.g., Hooft, 1972; Mathisen et al., 1982), they are primarily based on the strip theory (or pure Morison equation) neglecting three-dimensional wave interactions between the Morison elements. Considering the co-existence of large-diameter columns and small-diameter members, it is advisable to employ a hybrid approach combining the potential flow theory and the Morison equation (Li and Yu, 2012). Liu et al. (2016) have done such a hybrid modeling in the frequency domain. The present work extends the idea to the time domain for a complex floating structure.
Ji, Chong (School of Naval Architecture, state key Laboratory of Structural Analysis for Industrial Equipment, Dalian University of Technology) | Jiang, Sheng-chao (School of Naval Architecture, state key Laboratory of Structural Analysis for Industrial Equipment, Dalian University of Technology)
In this paper, the near-trapping phenomena associated with four-cylinder structures affected by the side-wall of wave flume are investigated. The linear potential flow and the viscous fluid flow models are adopted, by which the difference between two numerical results with and without side-wall effect is compared. Numerical simulation shows that the side-wall has significant effect on the near-trapping phenomenon, including the free surface distribution and wave forces on the boxes. The general variation of wave amplitude around the structure and wave force on the box can be obtained by the potential flow model. However, it over-predicts the peak value around the frequencies where near-trapping and side-wall resonance happens. The comparisons of maximal wave amplitude and wave force by two numerical models with and without side-wall effect are performed in this work. The influence of the sidewall is much greater than that of the fluid viscosity can be observed.
In recent years, the exploitation of offshore resources has gradually developed into deep sea areas. Traditional jacket and jack-up offshore platforms cannot meet the engineering needs of deep-sea resources development. Floating offshore platforms, including tension legs and semi-submersible platforms, has attracted more and more attention. These platforms are usually composed of four large-diameter columns that provide buoyancy and restoring torque through large displacement. Under some severe sea conditions, the wave run-up has an impact on the lower deck of the platform, generating a large acting force and overturning moment. However, in order to avoid the excessive wind area of the platform caused by the high center of gravity, the design of the air gap of the platform should not be too large. Therefore, it is the key to the design of floating offshore platforms to fully consider the force of the supporting column under the action of waves and the change of the nearby free water surface. For the cylinders arranged in an array, the front row of cylinders mainly has a shielding effect that reduces the force of the rear row of cylinders, while the cylinders located in the same row mainly have the interference effect of increasing wave force. However, for large-diameter floating platforms, due to the strong influence of wave diffraction, the traditional method of ignoring wave diffraction based on small-scale objects cannot meet the calculation needs of large-scale objects.
Maritime rescue is usually dangerous and difficult. In order to ensure the safety of rescue, a two dimensional simulation of two Wigley in numerical wave tank is made to predict the ship motion. Base on the Navier-Stokes equations, VOF model and overset method, the motion of two ships was simulated in time domain. The effect of different distance of two ships, different wave period and different wave height is researched. It is found that the increase of distance and wave height will increase the amplitude of the ship motion.
When the rescue ship assistant accident ship, such as transporting the wounded, delivering the supplies or carrying out some other operation, two vessels would have to come to a relatively close proximity. The relative location of two ships is similar to the FPSO–shuttle tanker system (Koo, Kim,2005), however both of the ships are unconstrained. In the situation that the weather is terrible, the progress is actually dangerous for the ships would move violently. In order to avoid the accident, it is necessary to predict the motion of ships.
The multiply body question has been searched for a long time. Hong and Kim (2005) proposed a higher-order boundary element method (HOBEM) and certificate it by experiment. The result shows that the simulation based on HOBEN has a good agreement with the experiment result in ship motion and wave drift force except for the wave drift force in the narrow gap between two ships which has a strong interaction due to Helmholtz resonance. Chen (2005) proposed the damping lid method. He added a dissipative term in the free surface boundary condition inside the gap to get a better accuracy in wave drift of the narrow gap of two ships. After that, studiers start to solve the problem in time domain. Nam and Kim (2016) simulated the berthing progress of the FPSO and shuttle tank in time domain. By using re-mesh algorithm method, they make the calculation more efficient. Pessoa and Fonseca (2016) studied the second order low frequency relative motions between the vessels and related mooring line tensions. Yue，Kang et al (2020) discuss the situation that one FSRU connected with the LNGC by cables. Moreover, the uncertainty analysis is discussed by experiment two model ship in towing tank (Qiu, Meng, Peng and Li,2019).
Sempra Energy’s Energía Costa Azul LNG (ECA LNG) subsidiary reached a final investment decision (FID) to build its $2-billion Phase 1 natural gas liquefaction export project in Baja California, Mexico. ECA LNG, a joint venture between Sempra LNG and its Mexico subsidiary IEnova, is the only LNG export project to reach FID in 2020, and is slated to be the first on the Pacific Coast of North America. The facility will connect natural gas supply from Texas and the western US to Mexico and other countries across the Pacific Basin. First production from Phase 1 is expected in late 2024. The company secured a 20-year supply agreement with Mitsui and an affiliate of Total for the purchase of 2.5 mtpa and is working with Total for a potential equity investment in the facility.
Petrobras is offering a 50% stake in its Marlim complex located offshore Brazil in the Campos Basin. The deal is part of the company’s plan to optimize its portfolio, improve capital allocation, and shift its resources to deep and ultradeep waters. Marlim is the third offer the company has made over the past five weeks following its notices for the Bahia Terra and Carmópolis clusters. The offshore development is the third largest in Brazil and fourth largest in the Americas by production, with potential for future activity including near-term field revitalization and pre-salt potential. It’s also the largest post-salt development in Brazil with more than 20 billion bbl of original oil in place (OOIP) and includes licenses through 2052 with potential to increase the current production of approximately 120 million BOE/D by about 60%.
ADNOC LNG signed a supply agreement for up to 6 years with Vitol for the sale of 1.8 mtpa of post-2022 LNG volumes, and a 2-year supply agreement with Total for 0.75 mtpa of 2021 and 2022 LNG volumes. The agreements continue ADNOC’s transition to a multi-customer strategy that began in 2019, and follow its investment partnership with Vitol in global storage terminal owner and operator VTTI. Since then, the company shifted from supplying 90% of its LNG to Japan to supplying 90% of LNG to clients in more than eight countries from across southern and southeast Asia. The agreement is also in line with its 2030 gas strategy to deliver value for UAE and meet global demand, which is expected to grow by up to 5% annually over the next 20 years. ADNOC LNG, owned by ADNOC (70%), Mitsui & Co (15%), BP (10%), and Total (5%), produces about 6 mtpa of LNG from its Das Island facilities off the coast of Abu Dhabi.
The Abu Dhabi National Oil Company (ADNOC) completed the first phase of its large-scale multiyear predictive maintenance project to improve asset efficiency and integrity across its upstream and downstream operations. Announced in November 2019, the project is being implemented over four phases as part of the company’s digital acceleration program to embed advanced digital technologies across its operations. Phase 1 covers the modeling and monitoring of 160 turbines, motors, centrifugal pumps, and compressors across six ADNOC Group companies. All phases of the project are expected to be completed by 2022 and will enable monitoring of up to 2,500 critical machines. Using artificial intelligence (AI) technologies including machine learning and digital twins, the company’s predictive maintenance platform helps with equipment stoppages, reduces unplanned equipment maintenance and downtime, increases reliability and safety, and is expected to deliver maintenance savings up to 20%.
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
This paper focuses on solutions and strategies for conserving weight and space, reducing emissions, and leveraging data to optimize the performance of rotating equipment on floating, production, storage, and offloading (FPSO) vessels. It discusses design considerations for gas turbines in offshore applications (i.e., dry-low emissions technology, use of lightweight components, etc.) The paper also outlines a holistic digital lifecycle approach to FPSO topsides, which can help reduce capital and operating expenses, shorten project development cycles, and decrease offshore manpower requirements.
For illustrative purposes, the paper discusses specific power and compression solutions that were implemented on various offshore projects in 2017 - 2018, ranging from Offshore Brazil to the Bering Sea. It outlines how the equipment configurations helped operators meet horsepower requirements and emissions targets, as well as CAPEX and OPEX objectives. Additionally, the paper discusses how digital transformation can be leveraged to optimize FPSO lifecycle performance, delivering benefits such as 4-12 week reduction in project cycle times, ~$7 million reduction in CAPEX, and $60 - $100 million reduction in OPEX over a 10-year period.