bluuebunny/crossref_metadata_2025 huggingface dataset:
Suction Caisson Anchor and Dynamically Installed Fish Anchor in Calcareous Silt
Authors: Hossain Muhammad Shazzad , Mohiuddin Mohammad Arif , Chang Kuntan , Koh Kaixiang , Kim Youngho
Published: September 2023

Suction caisson anchors are proven reliable anchoring solutions for tethering floating facilities in shallow to deep water. Dynamically installed anchors have been identified as the most cost-effective option for particularly deep water developments. Recently, the dynamically installed fish anchor has been introduced, adopting a geometry taken from nature. Physics for installing these two anchors are different. However, owing to the counterbalancing effects of strain rate dependency and strain softening the operative undrained shear strength around these two anchors may be similar. After the completion of installation, for suction caisson anchors, the skirt is embedded in the seabed with a soil plug inside and the lid sits on or slightly above the mudline, and for dynamically installed anchors, the whole body is mostly fully embedded into the ground. Furthermore, under operational loadings, the fish anchor is found to dive (penetrate deeper) in the seabed deposit. These different embedment conditions and potential diving for the fish anchor cause differences in the behaviour and mobilised capacity under operational monotonic and cyclic loadings in calcareous silt.
Proposal for Motion Stabilized Platform of Doppler Lidar for Offshore Wind Observation and its Validation
Authors: Yamamoto Yusuke , Kinugasa Mizuki , Morota Hiroki , Katayama Toru
Published: September 2023

In this study, a rigid body swing with motion control as a motion stabilized platform of Doppler Lidar to place on floating platform is investigated. First, a counter-weight type motion stabilized platform is proposed, and its effectiveness of motion reduction on a spar-buoy type floating platform with tension-mooring is confirmed by numerical simulations and model tests. Furthermore, skyhook damper and spring controls are applied to the motion stabilized platform to optimize its motion, and it is confirmed by numerical simulations that its effectiveness of motion reduction is significantly increase. Finally, the motion stabilized platform is set on a discus-type floating platform whose motion is much larger and complicated than a spar-buoy type floating platform and its effectiveness is also confirmed by numerical simulations.
Application of Drilling Fluid Circulation Technology to Lifting System for Deep-Sea Mineral Resources
Authors: Kitago Ryuta , Naganawa Shigemi , Bjarkason Elvar Karl
Published: September 2023

Various types of deep-sea mineral resources such as mud containing rare earth elements, manganese nodules, cobalt-rich crusts, and methane hydrate are found on deep-water seabeds around the world. Lifting systems for mining these resources using a gas lift approach or submersible pumps have been studied by many researchers. As an alternative to these lifting systems, this study proposes a rare earth mud lifting system using a hydraulic jet pump, like those used for artificial lifting in oil wells. The objective of this study is to investigate the design of this lifting system to maximize the mud suction rate of the hydraulic jet pump by numerical simulation. The hydraulic jet pump simulations involved two-phase flow of seawater as the working fluid and rare earth mud slurry as the production fluid. The simulation results showed that all the considered hydraulic jet pump designs could suck in highly viscous rare earth mud slurry at an ocean depth of about 7,000 m. A design with three sets of suction lines and diffusers gave the best performance and could transport a rare earth mud slurry at commercially viable combinations of flow rates and mud concentrations. At a suction line diameter of 1″, the produced mud rate exceeded the commercial reference standard, with mud recovery rates of 10,500 ton/day and 15,800 ton/day when the volumetric mud concentration of the slurry entering the pump was 20% and 40%, respectively.
A Study on the Fracture Toughness Evaluation Considering Material Tensile Characteristic for Cryogenic Steel
Authors: Kim Ji Hoon , Jeong Young Cheon , Cho Dong Pil , Kim Myung Hyun
Published: September 2023

ISO 12135, a representative standard for the evaluation of fracture toughness, was revised in 2021. In the previous standard published in 2016, only yield strength was reflected for material property in fracture toughness calculation. In the revised standard, however, yield to tensile strength ratio is additionally reflected in consideration of strain hardening effect of the material. The current fracture toughness calculation formula evaluates fracture toughness reasonably considering the tensile characteristic. However, in some cases of cryogenic steels, fracture toughness is evaluated very conservatively than the previous procedure in 2016. In the case of STS 304L, there is no ductile-brittle transition phenomenon and it has excellent ductility and strength in cryogenic temperature. However, due to the secondary hardening phenomenon, yield to tensile strength ratio is relatively low, and as a result, fracture toughness is evaluated very low. The target of this study is to resolve the undervaluation of fracture toughness of cryogenic steel in the revised ISO 12135. For this purpose, the elastic and the plastic parameters in CTOD equation in ISO 12135 is examined. The crack tip profile is derived by a series of finite element analysis and crack tip opening displacement is calculated for the derivation of new parametric equations for cryogenic materials. The calculated crack tip opening displacement is validated by experimental results.
Demonstrating Electrically Heat-Traced Flowline (EHTF®) Performance – As-Built Engineering Versus Field Data, the Perfect Match
Authors: Mencarelli Guy , Minier Yves , Silcock Donald , Pradeilles Camille , Michel Xavier , Gibson David
Published: September 2023

As part of the Aker BP Skarv field development, the Ærfugl phase 2 project is a 13km tie-back requiring an electrically heated flowline to provide a reliable and cost-effective hydrate management solution.

This paper will present at first the reverse engineering work done on the thermal and electrical performances of this first generation of EHTF® system based on field data. In production since November 2021, operational feedbacks on the highly insulated Pipe-in-Pipe associated to the distributed temperature monitoring system have been used to confirm the passive thermal performance of the system as targeted and predicted by design. In addition, data gathered during the performance tests performed in May 2022 as part of a planned production shutdown have been processed; the results clearly demonstrating the perfect match between predicted system performances using Subsea7 design & engineering models and recorded topside electrical parameters and subsea heating performances.

Then, based on those robust engineering models, typical EHTF® performances will be presented to provide more insights on achievable EHTF® system capabilities.

This is indeed a key achievement demonstrating the maturity of the technology and providing to operators an increased level of confidence in the EHTF® technology and in Subsea7’s design, fabrication, and installation abilities to deliver EHTF® solutions on future field developments as specified and planned.

To conclude, the paper will present the next generation of EHTF®, achieving longer tie-back distances while capitalizing on the first-generation knowledge and technology.
Investigation of Simulation and Tank Tests for Motion Behavior of Semi-Submersible Platform DeltaFloat With a 10 MW Wind Turbine
Authors: Huang Zheng-Zhang , Chou Shean-Kwang , Chung Cheng-Hsien , Wu Hua-Tung , Hsu Hao-Teng , Wu Yan-Wen , Chiu Forng-Chen
Published: September 2023

The government of Taiwan is promoting developments within offshore and coastal structures, which includes developments within the floating offshore wind turbine (FOWT) sector. The aim of the development plan is to lower the FOWT lifetime cost of energy so they eventually are competitive with bottom-fixed wind turbines. Model test of design concepts and verification of numerical software are important aspects of such developments. The present study investigates the existing design concept using both numerical software and experimental tank tests. By examining the potential site condition, where Hsinchu waters are specified as well as manufacturing capabilities and infrastructure in Taiwan, the semi-submersible platform DeltaFloat used for DTU 10 MW wind turbine is proposed.

In order to compare the design of a floating wind turbine accurately, a water tank model test is planned to verify the motion behavior of the design. The motion response and free decay of the floating platform structure are discussed. By establishing a floating platform model and instruments, free motion decay and regular wave tests were conducted, and then the motion behavior of the floating platform and the tension of the mooring chain were measured. The test results were compared with the simulated ones, which show good approximation.
Deep Learning Based Prediction of Hydrodynamic Forces on Offshore Platforms
Authors: Miyanawala Tharindu Pradeeptha , Li Yulong , Law Yun Zhi , Santo Harrif
Published: September 2023

Irregular ocean waves cause fluctuating non-linear hydrodynamic forces on the body, which is an importance factor to account for in offshore and marine applications. While physical experimental and computational techniques provide valuable physics insight, they are generally time-consuming and expensive for design space exploration. We present an efficient Long Short Time Memory (LSTM) based deep-learning technique to predict unsteady hydrodynamic forces on slender bodies, where drag forces are more dominant than inertia forces. A leaky non-linear rectification is employed to approximate the mapping between surface elevation time series and hydrodynamic (drag) force time series. The deep neural network is fed with irregular waves based on JONSWAP spectrum as the input and the target data generated by the full-order Navier-Stokes computations using a generic offshore jack-up platform. The LSTM is trained using a stochastic gradient descent method to predict time series of the hydrodynamic forces on the jack-up and the results are compared with the full-order computations. Within the error threshold, the predictions based on our deep convolutional network have a speed-up of nearly 2 orders of magnitude compared to the full-order results and consume an insignificant fraction of computational resources. Overall, the proposed LSTM-based approximation procedure has the potential to be used for parametric design and digital twinning of jack-up platforms.
Using Non-Linear Finite Element Analysis to Analyze the Effects of Connection Designs on the Ice Strength of a Vessel
Authors: Gosse Joshua , Quinton Bruce , Daley Claude , Kendrick Andrew , Bond James
Published: September 2023

As global temperatures rise, ice clears in the Arctic Ocean and the demand for Canadian Coast Guard presence in the Canadian Arctic increases. The Canadian government intends to acquire two new heavy icebreakers as part of the “Polar Icebreaker Project”. These icebreakers are to be built to IACS Polar Class 2 standards. Some classification societies require fully welded collars to support stiffener penetrations through deeper hull structure in the ice-strengthened region of the ship. This, however, is a labour-intensive, material-heavy, and thus costly way to manufacture these vessels. This study analyzes hull structural response for three alternative penetration support details and compares these with the base case for a fully welded collar. The goal is to determine if there is a more cost-effective and less material-intensive way to implement these penetrations while maintaining the stiffness of a fully welded collar. A three-dimensional model of the port side ice strengthened structure of a Polar Class 2 vessel was investigated. A design ice load pressure patch based on the International Association of Classification Society’s unified rules for polar class was applied to the structure using finite element analysis. Results show that two of the three alternative connection designs gave unsatisfactory performance but that alternative connection designs with less steel and less welding can maintain acceptable structural strength.
Frequency Domain Analysis and Machine Learning Technique in Field Fatigue Monitoring of Flexible Risers
Authors: Yuan Jiabei , Zhu Linfa , Hou Yucheng , Tan Zhimin , Wilson Eric
Published: September 2023

Field fatigue monitoring of flexible risers has been gaining more interests in the offshore industry. Traditionally, monitoring is based on time domain simulation, where real-time loading data (environmental and functional) are collected and converted into time history stress and strain results of the strength components of the pipe and the subsequent accumulative damage. The time domain approach, with real-time input data, does produce more realistic fatigue results but at the cost of time-consuming simulations which may cause a lag between input data (realtime) and the fatigue results (computed).

This paper presents an application of the frequency domain approach in online fatigue monitoring of flexible risers to reduce computational effort. The study is focused on the tensile wire as these layers usually exhibit larger fatigue damage than other layers. The frequency domain method was implemented in fatigue analysis with an Artificial Intelligence (AI) technique, where guided machine learning is used to establish the responses pattern of the tensile armour wire along its configuration. With enough data captured, the field analysis can reduce the calculation to certain locations to speed up the computation and reduce the lag. Fatigue damage accumulation at other locations can be predicted by the trained model.
A Roadmap for Replacing Legacy Assets Using Metal Additive Manufacturing and Rapid Casting: A Case Study From the NCS
Authors: Karlsen Jon Erik , Mudiyanselage Chandima Ratnayake
Published: September 2023

Legacy, obsolete, or undocumented assets are an increasing liability for ageing offshore installations on the Norwegian Continental Shelf (NCS). It has become an untapped resource for suppliers that aim to provide a one-to-one replacement or original component modification by Metal Additive Manufacturing (MAM) and Rapid Casting (RC). Acquiring MAM assets for the Norwegian Energy, Oil & Gas (EO&G) industry with an on-demand solution requires a comprehensive understanding of standardization, manufacturing, and digitalization. However, the overall awareness and integration of the aforementioned areas are diffuse. The study focuses on the literature review, investigating the requirements and challenges of providing the framework for an on-demand solution and developing a roadmap for NCS stakeholders. The roadmap enables users to improve their understanding of the overall on-demand supply chain and the decision-making capabilities that enable using MAM and RC to replace legacy assets on request. This manuscript also demonstrates the criticality level selection for MAM of items proposed based on the committee “F42 on Additive Manufacturing Technologies” and load-bearing components in aviation. The roadmap includes a flow chart indicating the activities governing the manufacturing of legacy assets. The findings in this study are helpful for EO&G stakeholders and practicing engineers in developing internal work processes for providing on-demand spare parts solutions to the EO&G industry on the NCS, where the identified roadmap would replace legacy assets through a reverse engineering process in a digital warehouse environment.
Offset-Free Tracking Control for a Marine Autonomous Surface Ship
Authors: Islam Tanjil , Imtiaz Syed , Ahmed Salim , Islam Mohammad , Zaman Hasanat , Gash Robert
Published: September 2023

The importance of autonomous surface vessels is increasing day by day because of more and more missions and safety concerns. An offset-free control system is essential for a Marine Autonomous Surface Ship (MASS) to follow its desired trajectory. The position, yaw angles, and desired velocity are the main parameters that need to be controlled precisely to keep the ship on course in the presence of environmental disturbances. In this current research, we propose an advanced control system for surface vessels that is versatile and can achieve a broad range of operational objectives while obeying safety constraints. A Nonlinear Model Predictive Control (NMPC) is the heart of our proposed system. The NMPC solves a quadratic optimization problem and dynamically calculates the control actions considering the safety constraints of the vessel. The conventional way of calculating the yaw angle and the line-of-sight guidance method for the same are compared when the trajectory tracking results are simulated in the presence of disturbances to test the performance of the controller. Such controllers are expected to provide substantial benefits by providing less operational cost, enhanced safety, and efficiency.
Preparation of a Synthetic Geo-Polymer Based LCM Utilizing Saudi Arabian Volcanic Ash for a Sustainable Development: Method, Lab Testing and Applications
Authors: Alanqari Khawlah , Al-Yami Abdullah , Wagle Vikrant
Published: September 2023

We successfully developed a novel geo-polymer based LCM to treat moderate to severe losses. Geopolymers can be prepared utilizing waste materials such as fly ash. In Saudi Arabia, we have enough volcanic ash to sustain the development of the geo-polymer based LCM. This novel LCM was prepared by utilizing a Saudi Arabian volcanic ash. The volcanic ash particles were activated with an alkali solution to undergo a geo-polymerization reaction. The geo-polymerization was designed to delay and successfully controlled to gel up and form the target geo-polymer barrier after the fluid goes inside the wellbore. This is very important to avoid an early setting of the fluid. The objective of this paper is to discuss the formulation and preparation of the geopolymer barrier as a lost circulation material. Also, to investigate the effect of both the addition amounts and concentration of the activating solution on the final geopolymer physical properties as well as to detail lab testing.

Saudi Arabian volcanic ash particles were activated by a mixture of NaOH, sodium silicate and water to develop a geopolymer barrier. In this study, we prepared four different activating solutions by varying the alkali concertation and the addition amounts based on the volcanic ash chemical composition. The effect of these variations on the geo-polymerization in terms of setting time and rheological properties of the final geopolymer barrier were investigated. This was done to develop a geo-polymer barrier with a delayed and controlled setting to assure a right placement inside the wellbore. In addition, the chemical conditions were evaluated to simulate a variety of downhole conditions to prove the effectiveness of this novel geo-polymer composition as an LCM to treat moderate to severe losses. The lab testing includes thickening time, rheology, compressive strength and a chemical analysis of the Saudi Arabian volcanic ash. We found that thickening time and rheological properties of the final geo-polymer barrier are strongly affected by the alkali concentration and the addition amounts of the activating solution. This novel geo-polymer barrier can remain in a liquid phase from a few minutes to several hours based on the desired conditions. The final and target geo-polymer barrier will appear and gel as a solid thereby preventing loss circulation.
Manufacturing Method Selection for Mechanical Legacy Assets Aimed at the Norwegian Continental Shelf
Authors: Karlsen Jon Erik , Mudiyanselage Chandima Ratnayake
Published: September 2023

Introducing disruptive manufacturing technologies such as Metal Additive Manufacturing (MAM) and Rapid Casting (RC) for legacy assets to the Norwegian supply chain for energy, oil, and gas is challenging without a track record. Therefore, it becomes a requirement to re-engineer and manufacture parts “just-in-time” (or on-demand) that are currently not produced by the original equipment manufacturers (e.g., offshore facility components made in the 1970s and 1980s, etc.). This study demonstrates the selection of a just-in-time manufacturing method for a critical asset (i.e., a valve body) that needs to be manufactured for the offshore facility Statfjord-A, built in the late 1970s. The technical experts have concluded that MAM and RC are potential methods for critical asset manufacturing. The two benchmarking manufacturing options have been evaluated using the Analytic Hierarchy Process (AHP) to select the most suitable method for the asset. Furthermore, the AHP outlines the options for MAM and RC that involve essential criteria for manufacturing method selection based on feedback from industry experts (i.e., asset owners and suppliers). Expert Choice was used to compile the developed manufacturing method criteria hierarchy and is presented together with a criteria sensitivity analysis. The findings displayed that the criteria for environmental impact must increase by 32.5% relative to the other criteria to make RC and MAM equally selectable. In comparison, the criteria for cost and volume of material must decrease by 46% and 6.8%, respectively, for RC and MAM to be equally competitive. The outcome of the overall AHP analysis reveals that RC (63%) scored higher than MAM (37%).
An Efficient Three-Dimensional CFD-Based Numerical Wave Tank for a Wave Energy Converter in Extreme Irregular Waves
Authors: Wiley Will , Tran Thanh Toan , Boerner Thomas , Weston Collin , Wang Lu
Published: September 2023

A numerical wave tank approach for computational fluid dynamics (CFD) modelling of an extreme irregular seastate is presented. The technique couples a potential flow solution with a CFD solver for more efficient numerical predictions. This method has recently become attractive both for the research community and the industry working with offshore structures. The model is used to determine the response of a submerged pressure differential wave energy converter (WEC) in a fully nonlinear irregular wave condition using the high-fidelity CFD code, STAR-CCM+. Potential flow based numerical models are commonly used to predict motions and performance of wave energy converters. Wave kinematics can deviate from potential flow predictions for extreme wave conditions; the excitation loads on an absorber can also be increasingly influenced by viscous effects, not predicted by potential flow engineering level models. In these extreme conditions, a Reynolds-averaged Navier-Stokes CFD model can better predict motions and loads for a WEC. Long time series with varying random seed numbers can be used to identify singular extreme wave events from a stochastic irregular sea state. This approach simulates a more realistic wave series for a given sea state than a regular wave or a focused wave. However, it is computationally infeasible to run these long time series for three-dimensional (3D) CFD simulations. In this work, two-dimensional (2D) CFD simulations with a long domain allow the full development of an extreme nonlinear wave condition. The results are used to identify extreme events from a 50-year storm condition for the PacWave site off the coast of Oregon. A relatively short time window including this extreme event is then mapped to a 3D simulation using a user defined wave methodology. Convergence studies for domain length, wave forcing lengths, and time before the extreme event were conducted.
Wave-Current Interaction With Floating Objects With Square and Circular Waterplane Areas
Authors: Lamei Azin , Li Shuijin , Hayatdavoodi Masoud , Riggs H. Ronald
Published: September 2023

Floating pontoons of different shapes are used commonly as the base of floating offshore wind turbines, and as wave breakers to mitigate severity of incoming waves. The pontoons are typically attached to catenary mooring lines and often operate in areas subject to large environmental loads, including waves, current and wind. It is of interest to analyse the wave-current interaction with pontoons of various shapes, and assess the effect of the shape of the body, wave-current direction, and the mooring lines on the loads and responses. In this study, attention is confined to wave-current interaction with floating objects with square and circular waterplane areas. A range of wave conditions is considered and the solution is obtained by the Green-function method for small forward speeds within the context of the linear wave diffraction theory. Results include the wave-current-induced forces, and the motion of the body. Both conditions of freely floating and objects attached to catenary mooring lines are considered, subject to various wave-current directions. Computations are carried out in frequency domain and results of the two models are compared with each other. Discussion is provided on the effect of the mooring lines and the wave-current direction on the responses of the objects.
Comparison Study of Shallow Water and Deepwater Mooring Systems for Floating Offshore Wind Turbine
Authors: Kim Hyoungchul , Koo Bonjun , Sablok Anil , Lim Ho-Joon , Laihomäki Tapio
Published: September 2023

The offshore wind industry trend is towards larger wind turbines to lower the Levelized Cost of Energy (LCOE). The water depth plays an important role in Floating Offshore Wind Turbine (FOWT) project viability due to mooring system cost. In the present study, a comparison of shallow water and deep water mooring systems is performed for the offshore US West Coast.

To perform the comparison, two mooring systems for 150m and 1300m water depths are designed for a 15MW semi-submersible type FOWT. For comprehensive mooring system performance comparison, a response-based direct time domain simulation method is applied using MLTSIM-OpenFAST in conjunction with High Performance Computing (HPC). MLTSIM-OpenFAST is a time domain aero-hydro-servo-elastic solver for a FOWT and has been validated through OC3 DeepCwind model tests.

For metocean conditions, 1-year hindcast wind, wave and current data with 3-hour intervals from WAVEWATCH III® hindcast data and HYCOM (Hybrid Coordinate Ocean Model) are used. Based on simulation results, aero-hydro-servo-elastic fully coupled responses of the 15MW FOWT with two different mooring systems are systematically compared. In addition, high-level mooring system cost comparisons are performed. The platform motions other than the platform offset and yaw are similar in both cases along with the Tower Base loads. Similarly, the probability distributions of power generation are similar for both cases. In terms of mooring cost, a deepwater mooring system can be competitive compared to a shallow water mooring system.
A Feasibility Study on Green Energy Production at the Location of Offshore Oil and Gas Platforms in Australia
Authors: Aryai Vahid , Abdussamie Nagi , Abbassi Rouzbeh , Penesis Irene , Wang Chien-Ming , Garaniya Vikram
Published: September 2023

An important aim of the offshore energy sector is to replace oil and gas production with sustainable and environmentally friendly energy production. The public expectations and the international environmental agreements enforced all sectors of the governments to encourage the transition from fossil fuel production to renewable energy production. Green energy production alternatives by transforming/repurposing available offshore oil and gas platforms in Australia is essential for a successful blue economy. This research aims to explore the potential for generating green energy at the location of offshore oil and gas platforms that exist in different oil and gas basins around Australia. To this aim, the locations of seven platforms, one from each basin, are selected as case studies, and the potential energy production by using wind, wave, and solar energy conversion systems in the vicinity of the existing platforms is estimated. Furthermore, the green hydrogen production alternative is investigated in the case of repurposing the existing platforms as a storage, distribution and export multipurpose offshore platform. Finally, discussions on the other requirements for selecting target options for repurposing offshore oil and gas platforms are presented.
Offshore Oil Wells: Indicators for Configuration Selection
Authors: dos Santos Joaquim Rocha , Taverna Martins Pereira de Abreu Danilo , Colombo Danilo , Ramos Martins Marcelo
Published: September 2023

Brazil’s most productive oil fields are found in the pre-salt cluster, located at approximately 7,000 meters, with a water depth of around 2,000 meters. Offshore operations under these conditions represent a major technological challenge. If, on the one hand, the production of these wells is very attractive, generating significant revenue, on the other hand, maintenance costs and the risk of accidents are also high. In order to operate under these conditions, operators must make every effort to operate wells with a reliable integrated set of barriers and high oil and gas production availability. An important phase of the oil well’s life cycle is the design. Several competing configurations are presented during this phase, and the decision-makers (DM) must choose the best option. A decision support software is under development to assist DM in this challenging task. A module of this software is intended to quantitatively assess three aspects: the integrity of the barrier elements; the reliability of production functions; and a financial indicator. This article deals with the financial indicator. The financial indicator is calculated from two sets of variables. The first set is informed by the oil and gas operator, such as the planning price of an oil barrel; the second set is from values calculated from a simulation module that uses the Monte Carlo simulation. To calculate the financial indicator, a System Dynamics model was developed. The article shows the DS model in detail, explores the model, and presents the results of an actual case used for testing, resulting in a difference of 8.9 million dollars between the two configurations. The conclusions comment on the assumption that oil and gas companies give great importance both in safety and operations continuity; also, that the result obtained for a single well may be relevant when considering a large number of wells, which is the case of great oil and gas operators; also, it is commented on the expandability of the model.
State-of-the-Art Methodologies for Upheaval Buckling Design of Flexible Pipes
Authors: Amdal Lars Wist , Pettersen Sune , Skeie Geir , Røneid Sigbjørn , Collberg Leif
Published: September 2023

Upheaval buckling (UHB) of flexible pipes has recently been identified as an area of concern for the Oil and Gas industry in the North Sea. The concern is related to non-conservative design practice and the possibility of pipe leakage. The phenomenon of UHB means that covered pipeline experience buckling in the vertical plane that may lead to exposure of the pipeline, and in worse case, pipe leakage.

Up until now there has been a lack of guidance and requirements that cover UHB design of flexible pipes. For guidance, the industry has been using DNV-RP-F110 ‘Global buckling of submarine pipelines’ to design flexible pipelines even though this document is written for rigid pipelines. Although the basic principles of DNV-RP-F110 should be applicable also to flexibles, the Recommended Practice (RP) does not account for particularities in flexibles pipes that are important to consider, e.g., the difference in bending stiffness between rigid and flexible pipes.

A Joint industry project (JIP) led by DNV was established to provide guidance on the required modifications when applying DNV-RP-F110 for UHB design of flexible pipes. The main deliverable of this work is a guideline. This paper will summarise the work performed in this JIP, thereby providing state-of-the art methodologies for UHB design of flexible pipes.
Energy Storage and Direct Air Carbon Capture Solution for Offshore Sources of Energy
Authors: Hands Graydon , Truong Kevin , Unico Yvan , Ashar Areeb , Al-Saiedy Ali , Shor Roman J.
Published: September 2023

Power intermittency associated with many forms of renewable energy has been a significant challenge to overcome since its increased contribution to our grids. Additionally, the global climate crisis driven by increased greenhouse gasses in the atmosphere has driven innovations into Direct Air Capture (DAC) technology which removes carbon dioxide directly from the air. The present report outlines a theoretical design for an offshore energy storage system which seeks to provide solutions to both of these challenges in a consolidated system.

The proposed system involves a motorized cable system built around an offshore wind turbine. Attached to the cable is a series of air balloons or “gondolas”. During times of excess energy production by the turbine, these gondolas are driven to a depth of 400 meters below the ocean surface. When energy demand increases, gondolas are released back up to the surface wherein a net upwards buoyant force recovers a portion of the energy input. Additionally, at maximum depth, hydrostatic pressure is large enough to condense the carbon dioxide content in the air, and the system is designed to separate and store it.

Iterative analysis indicates a system efficiency of 92.83% with a storage capability of 16.29MWh and a carbon recovery rate of 17.95 kg per cycle. Through cost analysis, the NPV of the system is found to vary dependent on implementation location and governmental incentives for a set payback period, ranging between $1.1 million and $3.1 million across Vancouver, Canada and Oslo, Norway. This technology has the potential to be very competitive with conventional Battery Energy Storage Systems (BESS) and Flywheel Energy Storage Systems (FESS).

In addition to this system design, our team has designed and will construct a prototype for one gondola which is planned to be field tested in the Summer of 2023.
Possibility of Tidal Farms for the Gulf of Kutch
Authors: Thiagarajan Vijaya Lakshmi , Samad Abdus , Rajendran Suresh
Published: September 2023

India has an extensive coastline of about 7500km, with locations such as the Gulf of Kutch, the Gulf of Khambhat, and Sunderbans, where tidal energy extraction is proven to be highly possible. According to the Indian Renewable Energy Development Agency (IREDA) report, India can harvest about 12.5GW of tidal energy. Among them, the Gulf of Kutch (GoK) shows a tremendous kinetic energy potential of nearly 2 GW. The goal of this review article is to provide a concise vision of the tidal stream farm development for the GoK. The scope of the study explores the availability of kinetic energy and bathymetric condition favourable for the deployment of the tidal farm. The study claims the substantial agreement of tidal energy harvesting of about 353 MW by a tidal farm with 642 turbines in the Central Gulf. It is found that the bottom-mount ed Horizont al Axis Tidal Turbine(HATT) as a part of the tidal farm shows a noteworthy reduction in capital cost than the previous estimation. The detailed site study evidence a promising outcome of the tidal stream farm in the location.
Techno-Economic Assessment of Developing Combined Offshore Wind and Wave Energy in Australia
Authors: Gao Qiang , Ding Boyin , Ertugrul Nesimi
Published: September 2023

Australia has significant offshore wind and wave energy potential that can provide a long-term solution to the ever-increasing power demand and contribute to the future energy mix. The integration of offshore wind and wave energy has been proposed previously, but considered to be difficult due to the high cost and high intermittency of developing ocean renewable energy sources. In addition, the economic analysis of the integrated offshore wind and wave systems, considering life cycle cost, energy benefits, market regulation costs and future carbon price, has not been studied thoroughly in Australia. Therefore, this paper aims to investigate the economic feasibility of a co-located offshore wind and wave energy farm in multiple key locations around the Australian coastline. The high-fidelity life-cycle cost and economic benefit models are developed under different technical deployment constraints. Furthermore, the paper studies the impact of electricity market regulation cost and future carbon prices on deploying the proposed combined energy farm. The results of this paper provide a guideline for industry leaders, investors and policymakers at the pre-planning stage of ocean renewable energy system development and deployment.
Carbon Footprint Reduction on Aging Offshore Facilities: Case Studies on Electrification and Carbon Capture
Authors: Vartak Viren , Loh SaiKeong , Repalle Nitin
Published: September 2023

Many of the existing Oil and Gas platform facilities installed in the late-1990s are powered by using conventional fuels like gas received and/or extracted from the production on the platforms. The gas is typically treated and reused to run operations on the platform, which results in increased CO2 emissions. Innovative concepts are needed to transform power generation from fossil energy to renewable energy for platform operations that will help reduce carbon footprint.

There are two ways to reduce the carbon footprint from production and maintenance operations. One way is to electrify oil and gas activities to minimise fossil-based systems. The other way is to collect the carbon generated from production operations and store it back in geological features such as depleted reservoirs or saline aquifers.

The paper introduces and discusses the successful implementation of renewable energy sources such as hybrid solar and wind to power operations for ageing platforms. The benefits of such electrification of facilities in terms of reduced maintenance visits, autonomous operations, and improved safety of personnel on the platforms and the environment are presented. A case study of a typical wellhead platform electrification based on hybrid solar and wind turbines to quantify the carbon reduction achieved from the switch is presented. An additional case study on an unmanned, lightweight minimum facilities platform is also be presented for carbon sequestration. The case study is focused on a typical 2.0 MMTPA CO2 injection platform.
An Efficient Time Domain Structural Assessment of a Floating Wind Turbine Structure
Authors: Lee Hyungtae , Kim Joongyu , Kim Jongoh , Shen Zhirong , Kyoung Johyun , Baquet Aldric , Lee Heejung , Kim Jang Whan
Published: September 2023

Unlike conventional offshore production platform, a substructure supporting floating offshore wind turbine has unique structural characteristics due to higher frequency aeroelastic loading from wind turbine in addition to wave loading. Due to periodic rotation of turbine, a floating offshore turbine substructure experiences higher fatigue load than conventional offshore platform. A reliable fatigue assessment is required to achieve the structural safety and integrity of the floating wind turbine platform. Accordingly, class societies recommend fully coupled time domain analysis because of nonlinear transient aeroelastic turbine behavior coupled with platform response in irregular waves. However, conventional coupled time domain structural analyses take huge computational resources and time, which is impractical to be applied in a floating wind turbine structural design.

Present paper introduces an efficient method for time domain structural assessment. An efficient pseudo-spectral stress synthesizer is introduced to accelerate time domain structural analysis, to enable response-based determination of the extreme structural responses. Through synthesizing the pseudo-spectral stress components with the time series of external and inertial loadings from global hull motion analysis, a time series of structural response is obtained efficiently in terms of stress components at any finite element of structural model. As an application, hot spot fatigue assessments of a floating offshore wind turbine platform designed for Korean offshore wind farm projects are performed.
Serviceability Limit State Assessment of Semi-Submersible Floating Wind Turbines
Authors: Wang Shuaishuai , Moan Torgeir
Published: September 2023

The design of a floating wind turbine (FWT) should satisfy the serviceability limit state (SLS) requirement for an efficient and safe operation throughout the entire work life. The SLS requirements are introduced by the owner/developer of the wind turbine facility to achieve serviceability (production of power) or an efficient operation of the facility or a “first step” towards ensuring safety. However, the owner/developer proposes the limiting values in terms of serviceability mainly according to the experience of onshore wind turbines or offshore oil and gas facilities, which are not well applicable to FWTs due to the different load characteristics and functions. Design standards or guidelines for SLS of FWTs are slowly emerging but are still not mature, and only to some extent refer to serviceability requirements. A good understanding of wind turbine dynamic performance associated with serviceability is essential to facilitate design decision-making. This study deals with an assessment of methods and criteria for the SLS design check with an emphasis on tilt/pitch and nacelle accelerations. Emphasis is placed on assessment from conceptual to detailed design. A 10-MW semi-submersible FWT is used in a case study. The floater geometry is obtained from a conceptual design conducted by Li et al. [1]. Simplified static/dynamic analysis methods for use in the conceptual design phase and high fidelity integrated, dynamic analysis methods for detailed design in terms of serviceability are presented, discussed and applied in the case study. The relative contribution of wind and wave loads to the different SLS criteria is investigated. Finally, the main conclusions are summarized. The study aims at providing a basis for improving design standards and guiding research and engineering practice for the semi-submersible floater design of FWTs.
Si-containing interlayer using tetramethylsilene for diamondlike carbon film adhesion on low-alloy steel: The role of the interlayer deposition time
Authors: Weber Jennifer Stefani , Piroli Vanessa , Goldbeck Michael Cristian , Perotti Bruna Louise , Boeira Carla Daniela , Fukumasu Newton Kiyoshi , Michels Alexandre Fassini , Figueroa Carlos Alejandro
Published: September 2023

Diamondlike carbon (DLC) coatings provide interesting properties for industrial applications. However, the low adhesion of DLC coatings on any type of ferrous alloy compromises technological applications. One possible solution to this issue is the application of adhesion interlayers. The aim of this study is to investigate the adhesion of DLC films on low-alloy steel through the use of silicon-containing interlayers at different deposition times using tetramethylsilane. The role of time on the physical-chemical, microstructural, and tribological properties of the material system was evaluated. The interlayer thickness linearly increased and greater contributions of silicon bonds were measured as a function of the interlayer deposition time. Nevertheless, longer deposition times increased the roughness and defect ratio in DLC coatings. Although good enough adhesion for decorative applications was acquired, no drastic variation in the average critical load (∼4.2 N) for delamination was observed at different deposition times for the samples that achieved adhesion.
β-Ga2O3 orientation dependence of band offsets with SiO2 and Al2O3
Authors: Wan Hsiao-Hsuan , Li Jian-Sian , Chiang Chao-Ching , Xia Xinyi , Hays David C. , Ren Fan , Pearton Stephen J.
Published: September 2023

Two of the most common dielectrics for β-Ga2O3 are SiO2 and Al2O3 because of their large bandgaps, versatility of preparation, and thermal stability. However, because of the anisotropic properties of the β-polytype, it is necessary to understand differences in band alignment for the different crystal orientation. Using x-ray photoelectron spectroscopy, we performed a comparative study of the band alignment of SiO2/β-Ga2O3 and Al2O3/ β-Ga2O3 heterojunctions with different β-Ga2O3 orientations of (001), (010), and (2¯01). The bandgaps were determined to be 4.64, 4.71, and 4.59 eV for the (2¯01), (001), and (010) oriented β-Ga2O3 substrates, respectively. The valence band offsets for SiO2 on these three orientations were 1.4, 1.4, and 1.1 eV, respectively, while for Al2O3, the corresponding values were 0.0, 0.1, and 0.2 eV, respectively. The corresponding conduction band offsets ranged from 2.59 to 3.01 eV for SiO2 and 2.26 to 2.51 eV for Al2O3.
Circulating fatty acids, genetic risk, and incident coronary artery disease: A prospective, longitudinal cohort study
Authors: Zhuang Pan , Liu Xiaohui , Li Yin , Wu Yuqi , Li Haoyu , Wan Xuzhi , Zhang Lange , Xu Chengfu , Jiao Jingjing , Zhang Yu
Published: September 2023

The role of fatty acids (FAs) in primary prevention of coronary artery disease (CAD) is highly debated, and the modification effect by genetic risk profiles remains unclear. Here, we report the prospective associations of circulating FAs and genetic predisposition with CAD development in 101,367 U.K. Biobank participants. A total of 3719 CAD cases occurred during a mean follow-up of 11.5 years. Plasma monounsaturated FAs (MUFAs) were positively associated with risk of CAD, whereas the risk was significantly lower with higher n-3 polyunsaturated FAs (PUFAs) and more reductions in risk were detected among TT carriers of rs174547. Furthermore, increased plasma saturated FAs (SFAs) and linoleic acid were related to a significant increase in CAD risk among participants with high genetic risk (genetic risk score > 90%). These findings suggest that individuals with high genetic risk need to reduce plasma SFAs levels for CAD prevention. Supplementation of n-3 PUFAs for CAD prevention may consider individuals' genetic makeup.
Understanding temporal changes and seasonal variations in glycemic trends using wearable data
Authors: Belsare Prajakta , Bartolome Abigail , Stanger Catherine , Prioleau Temiloluwa
Published: September 2023

Seasonal variations in glycemic trends remain largely unstudied despite the growing prevalence of diabetes. To address this gap, our objective is to investigate temporal changes in glycemic trends by analyzing intensively sampled blood glucose data from 137 patients (ages 2 to 76, primarily type 1 diabetes) over the course of 9 months to 4.5 years. From over 91,000 days of continuous glucose monitor data, we found that glycemic control decreases significantly around the holidays, with the largest decline observed on New Year’s Day among the patients with already poor glycemic control (i.e., <55% time in the target range). We also observed seasonal variations in glycemic trends, with patients having worse glycemic control in the months of November to February (i.e., mid-fall and winter, in the United States), and better control in the months of April to August (i.e., mid-spring and summer). These insights are critical to inform targeted interventions that can improve diabetes outcomes.