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Chenhao, Mao (School of Port and Transportation Engineering, Zhejiang Ocean University) | Binyu, Wang (Guangxi Vocational and Technical College of Communication) | Yunlin, Ni (School of Port and Transportation Engineering, Zhejiang Ocean University) | Yifan, Gu (School of Port and Transportation Engineering, Zhejiang Ocean University) | Hao, Zeng (School of Port and Transportation Engineering, Zhejiang Ocean University) | Wei, Chen (School of Port and Transportation Engineering, Zhejiang Ocean University)
The construction of wave dissipating platform would cause the sediment transport in the surrounding waters, changing the erosion and silting situation in the seabed, which may even lead to the abandonment of the original dock. In this paper, a 2D hydrodynamic and sediment transport model is established for Shengsi islands, Zhoushan and the surrounding area by using MIKE21. The model has well been validated through observation data of tidal level, flow velocity and direction. The influence of dissipating platform construction on the erosion and deposition of surrounding water is analyzed. The results show that the maximum diffusion envelope of suspended sediment (concentration higher than 0.02 kg/m3) in Huangsha village, Bianjiaoao and Huicheng village are 20,947.02, 19,799.04 and 5,311.35 m2 respectively. The project has little impact on the surrounding water quality environment.
The coastal construction has created enormous social and economic benefits, but the construction project has caused sediment transport in the surrounding waters, causing erosion and siltation changes which may even cause the original dock abandoned (Tsoukala et al., 2015; Plomaritis and Collins., 2013; Song et al., 2017; Zhang et al., 2005). Meanwhile, it exerts negative effects on marine ecological environment, arousing wide public concern of scholars (Sravanthi N, 2015; Yao et al., 2018; Gu et al., 2012; Tian and Xu, 2015).The suspended sediment produced during the construction process will form water masses with high suspended matter content within a certain range, weakening or even blocking the light transmission capacity of the water body, affecting the photosynthesis of phytoplankton. The reduction in the number of phytoplankton will cause a corresponding reduction of zooplankton. In addition, suspended sediment will attach to the surface of aquatic animals, interfere with their normal physiological functions, and more seriously enter the digestive system, causing death (Huang et al., 2019). Zhang (2015) used the ECOMSED model to simulate the terminal project of Shandong LNG project. The research obtained the maximum spreading range of suspended sediment produced by excavation of base trenches, stone dumping and dredging works during the spring and neap tides, and analyzed the impact of the project on marine life. Yan (2019) established a two-dimensional model by using MIKE21 FM, simulating the envelope area of the suspended sediment caused by the 10 kv submarine cable laying at Lvhua Island-Huaniao Island. The results show that the construction period has a greater impact on the marine ecological environment, and the service period has basically no impact on the marine ecology. In order to serve human life and protect the environment, numerical simulation has been widely used in engineering construction (Vu, Nguyen and Nguyen.,2020; Agrawal et al.,2019).
Shen, Wenjun (Tianjin Research Institute for Water Transport engineering, M.O.T) | Chen, Hanbao (Tianjin Research Institute for Water Transport engineering, M.O.T) | Jiang, Yunpeng (Tianjin Research Institute for Water Transport engineering, M.O.T) | Gao, Feng (Tianjin Research Institute for Water Transport engineering, M.O.T)
The ship to ship operation system of FSRU and LNG is taken as the research object in this paper. Based on the three-dimensional frequency-domain potential flow theory, numerical analysis of the resonance characteristics of wave surface elevation in the gap between FSRU and LNG. The effect of potential flow was modified by adding artificial damping, and the influence of wave period (wave frequency), incident direction and other parameters on the wave surface elevation was discussed. Furthermore, the problem of the resonance of the intermediate water body was further explored and analyzed based on the different distances between the two ships and different draughts.
Floating LNG storage and regasification unit (FSRU), which integrates LNG receiving, storage, transfer, regasification and export and other functions, it can used as LNG receiving terminal while it is moored at the dock and can also be used for the transportation of LNG. As the emergence of FSRU, it has become an important option for the receiving of LNG, and adopted by more and more countries and regions. According to statistics, up to now, there are 30 projects in operation and another 8 projects area being under construction.
In the loading and unloading operation period, ship to ship operation mode between FSRU and LNG is usually used, as shown in Figure 1. While this mode is used, the hydrodynamic interference and coupled motion between them are more complex. Especially when the two ships are very close to each other, the disturbance between the two ships is aggravated, which brings great safety risks to the loading and unloading operation. Therefore, it is necessary to consider the interaction of the hydrodynamic forces between the two ships, and know well about the hydrodynamic characteristics of the two ships in different conditions and the wave surface rise between the two ships.
Wei, Z. J. (State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology) | Shen, L. M. (State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology) | Du, X. P. (State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology) | Wang, Z. M. (State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology) | Zhai, G. J. (State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology)
In order to investigate the effect of the entrapped air on liquid impact, a series of experiments are designed and performed in an elastic rectangular tank under nearly 2D shallow-water condition. The evolution of free surface and the development of entrapped air near the vertical wall are recorded by the high-speed camera. Furthermore, the impact pressure and the wall deformation during slamming are measured. The results show that the presence of entrapped air can change the impact mode. Furthermore, the impact pressure and wall deformation induced by liquid slamming decreases due to the entrapped air, which shows the air cavity plays a cushion effect during liquid slamming. It is suggested to consider air compressibility during liquid slamming with entrapped air.
The challenges to design Floating Liquefied Natural Gas facilities have attracted enough attention from industry and academia. The FLNG is used for production, liquidation, storage and unloading offshore gas. Therefore, the FLNG system needs lager volume tanks and has no restrictions of filling condition. Liquid tends to slosh in a partially tank during shipping. Sloshing-induced slamming in a tank at low filling depth resulting in the structural local damage during FLNG shipping is one of the main loads in the design of super-large storage tanks (Gavory and De Seze, 2009). Thus, it is important to determine the slamming load and investigate the physical evolution of a wave impact during the sloshing process in a partially field tank. But during liquid impact, the physical phenomena with gas-liquid, gas-solid and gas-liquid-solid are complicated for researchers to predict the evolution of free surface and slamming load with theoretical and numerical methods (Abramson et al., 1974; Lee and Choi, 1999; Faltinsen and Timokha, 2009). For example, Delorme et al. (2008) numerically found that the maximum pressure calculated by their numerical method is greater than the experimentally measured values due to the presence of air. Therefore, from physical mechanics point of view, it is necessary to use experimental methods to study the liquid impact with entrapped air in the tank.
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).
Liang, Hui (Technology Centre for Offshore and Marine, Singapore (TCOMS)) | Chua, Kie Hian (Technology Centre for Offshore and Marine, Singapore (TCOMS)) | Wang, Hongchao (Technology Centre for Offshore and Marine, Singapore (TCOMS))
The fluid response at resonance in a narrow gap between two identical fixed barges is investigated for three typical wave headings including: beam sea, quartering sea and head sea conditions. A potential-flow model with energy dissipation effects is developed based on the boundary element method. The dissipation surface is devised at the bottom opening as well as two end openings of the gap, and both linear and quadratic damping terms are accounted for. Satisfactory agreement with experiments demonstrates that the response in the gap at resonance exhibits nonlinear correlation with the wave amplitude indicating the importance of the quadratic damping.
Liquefied Natural Gas (LNG) is an attractive source of clean energy, and it features easy transportation and relatively low carbon dioxide emission. The offloading of LNG from a floating LNG (FLNG) facility to a LNG carrier in a side-by-side configuration in the open sea is widely applied in offshore industry (Zhao et al., 2018a). Due to the presence of a narrow gap between the FLNG and LNG carrier, resonance of the partially-entrapped water column may occur under certain wave frequencies leading to large fluid motions in the gap. The consequence of large fluid motion may influence the relative motions of vessels, and induce large drift forces which in turn may pose various hazards that affect the cargo transfer operations (Kristiansen, 2009). The gap response is of particular interest because of strong resonant phenomenon where viscous dissipation effects may exert a significant influence.
The study of natural frequencies of standing wave patterns in the gap spurs the interests of researchers. Due to the narrow nature of the gap in between two vessels, the energy is trapped resulting in large response at resonance. Compared to the width of gap, the beam of the LNG carrier and FLNG can be assumed to be infinite. Under this assumption, Molin (2001) analytically studied resonant frequencies and natural modes for a side-by-side configuration in two dimensions and a rectangular moonpool in three dimensions, and explicit expressions were presented. To incorporate the end effect of two vessels, Newman and Sclavounos (1988) suggested that homogeneous Dirichlet conditions can be simply imposed at the ends (velocity potential equals to zero). Based on such assumption, Molin et al. (2002) derived an analytical formula to estimate the natural frequencies of gap resonance. Sun et al. (2010) verified Molin's formula numerically, and reported the sensitive hydrodynamic effects due to gap resonance. Zhao et al. (2017) experimentally studied the resonant fluid response in the gap driven by a transient focussed wave group, and observed that the duration of the liquid motion in the gap is much longer indicating the energy is partially trapped in the gap.
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.
In 2012, the International Energy Agency (IEA) released the ‘Golden Rules for a Golden Age of Gas’ - a set of best practice guidelines for unconventional gas development designed to address key environmental and social risks and gain public acceptance of the industry. This study sought primarily to understand the extent to which the experience of developing a large-scale coal seam gas (CSG) to liquefied natural gas (LNG) industry in Queensland, Australia was seen to have aligned with the Golden Rules, and how well the Golden Rules were seen to contribute to public acceptance of the industry.
An evaluation tool was developed where the seven Golden Rules and their subclauses were adopted as criteria in a scorecard approach. We conducted interviews with 32 senior people who had been directly involved in the development of the CSG industry in Queensland, from local, state and federal governments, gas companies, host communities as well as researchers and consultant ‘experts’.
The Queensland experience of unconventional gas development rated reasonably well in relation to the Golden Rules, with scores of three or higher out of five for four of the seven rule categories. Across all the Golden Rules, industry performance scored more highly than the effectiveness of the policy/regulatory environment, highlighting the complex and sometimes conflicted roles of governments in developing a new industry. The rules addressing baseline measurement, full disclosure and engagement were seen as most important for public acceptance.
This study developed a new tool to evaluate perceived social and environmental performance of industry and effectiveness of governance in unconventional gas development applicable across different jurisdictional contexts. This application suggests that baseline measurements, open disclosure and public engagement should be the focus for building public acceptance. For new gas developments, these findings highlight the importance of having a robust regulatory environment in place that can coordinate activities and manage cumulative impacts.
The sustained increase in global demand for cleaner fuels continues to drive the gas industry growth. Liquefied natural gas (LNG) has been a key enabler for this growth by making sizeable remote gas re-serves, which are unreachable by pipeline, accessible to the major and emerging gas markets. Every segment of the LNG supply chain has its own set of technical challenges. On the upstream side, many gas resources require significant pre-treatment before liquefaction, and the feed gas to the LNG facility is typically a mixture of various compositions from multiple sources; this composition mix evolves over the life of the project. The main challenge is development planning for the contributing reservoirs under the constraints imposed by the processing facility– managing reservoir deliverability, scheduling & sequencing of wells, and downtime management while maintaining the inlet stream specification. To aid with long-term planning for such assets, a virtual field management system is needed that can emulate a real-world hydrocarbon producing asset by capturing all operational constraints, resource lim-its, and complex operating logic.
This paper describes a comprehensive field management framework that can create an integrated vir-tual asset by coupling reservoir, wells, network, and facilities models and provides an advisory system for efficient asset management. The field management component can replicate any operational logic, exercises holistic control over the sub-surface model, integrates with the surface network model, and provides optimization capabilities. This paper demonstrates this for a complex LNG asset that is fed by sour gas of different compositions from multiple reservoirs.
We describe the different levels of constraints the asset needs to operate under, including treatment plant capacity, the LNG production capacity, the contractual LNG specifications, the disposal of gas impurities and imposes them on the model by utilizing a flexible and extensible logic framework. Con-straints applied at different levels can be mutually competing and their combination with recovery opti-mization goals increases complexity. The unified field management system uses a robust scheme to bal-ance the coupled system under these constraints while optimizing overall recovery. The optimization is enabled through the ability provided by the field management system to query and retroactively control flow entities during the simulation at the desired frequency.
Customization through scripting was necessary to implement this advanced logic and was enabled by the extensible nature of the field management framework. This extensibility, along with native capabili-ties, ensures that any level of complexity can be captured, and the workflow described in this paper can be applied to any hydrocarbon producing asset for short-term and long-term development planning.
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 Wheatstone Project is an LNG development located in Western Australia, incorporating the Chevron Australia operated Wheatstone and Iago fields and third-party gas fields. Production commenced in mid-2017. The start-up of the Wheatstone and Iago fields was a unique opportunity to acquire reservoir surveillance information that was able to provide valuable reservoir insights. A key component of the analysis was the observation of pressure interference between wells from the initial well clean-ups. The design of the well clean-up sequence, discussed in a previous paper (
The well clean-up sequence was executed safely and achieved the reservoir surveillance and operational objectives of the start-up program. Flexibility in the optimised well clean-up sequence allowed changes to the start-up strategy in response to changing operating conditions, without impacting the reservoir surveillance objectives.
High quality pressure interference data was acquired, enabling clear determination of zonal reservoir connectivity within the Wheatstone and Iago reservoirs. Interpretation of pressure interference results with reservoir models, incorporating Ensemble Variance Analysis led to a change in approach for initial history matching and revision of static and dynamic model development for Wheatstone and Iago fields.