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The complexity of offshore operations demands that offshore platforms withstand the variability and uncertainty of marine environments. Consequently, analyses of platform motion responses must extend beyond single sea state conditions. This study employs the Computational Fluid Dynamics (CFDs) software STAR-CCM+ for data acquisition and investigates platform motion from two perspectives: adaptability analysis to different wave directions and adaptability analysis to varying significant wave heights. The aim is to develop a model capable of predicting offshore platform motion responses across multiple sea state conditions. The results demonstrate that integrating the empirical mode decomposition (EMD) algorithm with residual convolutional neural networks (ResCNNs) and Long Short-Term Memory (LSTM) networks effectively resolves the challenge of insufficient prediction accuracy under diverse maritime conditions. Following EMD incorporation, the model's performance within the predictive range was significantly enhanced, with the coefficient of determination (R2) consistently exceeding 0.5, indicating a high degree of model fit to the data. Concurrently, the mean squared error (MSE) and Mean Absolute Percentage Error (MAPE) metrics exhibited commendable performance, further substantiating the model's precision and reliability. This methodology introduces an innovative approach for forecasting the dynamic responses of offshore structures, providing a more rigorous and accurate foundation for maritime operational decisions. Ultimately, the research enhances the safety and productivity of offshore activities. [ABSTRACT FROM AUTHOR]

In response to China's dual carbon call, the petroleum industry is committed to green transformation, promoting the energy green revolution, focusing on domestic offshore CO2 -enriched oil and gas reservoirs, and carrying out offshore platform carbon capture, utilization, and storage–enhanced oil recovery (CCUS-EOR) pilot projects. CO2 continuously displaces crude oil while being injected into deep-sea oil and gas reservoirs for carbon sequestration, achieving an increase in oil recovery and residual oil recovery. However, the implementation of offshore CCUS-EOR technology relies on the safe transportation of supercritical CO2 pipelines. Due to the unique physical and chemical properties of supercritical CO2 , the safe transportation of supercritical CO2 pipelines faces multiple threats. This paper focuses on the current status of safe transportation technology for supercritical CO2 pipelines on offshore platforms, and summarizes multiple operational challenges, including obtaining high CO2 gas sources, high construction costs of pipelines, complex phase change of media, and internal and external corrosion of pipelines. The risk factors for failure of supercritical CO2 pipelines on offshore platforms were systematically identified, and the mechanism of leakage hazards of supercritical CO2 pipelines was determined. Based on the six-step cycle of pipeline integrity management, a targeted integrity management method for supercritical CO2 pipelines on offshore platforms is proposed, providing reference for improving the safety transportation technology system of supercritical CO2 pipelines on offshore platforms. [ABSTRACT FROM AUTHOR]

The thermal medium oil expansion tank of an offshore platform was corroded and perforated. The cause of the perforation was analyzed through water sample analysis, tank opening inspection and other measures. The results showed that the main cause of the corrosion was the shedding of the oxide scale on the inner wall of the expansion tank head, which was immersed in fresh water, resulting in anaerobic microbial corrosion in the lower part. Maintenance suggestions, daily operation suggestions and new project suggestions, etc. were put forward to solve the corrosion problem of the existing expansion tank and avoid similar problems in new projects. [ABSTRACT FROM AUTHOR]

In the random sea environment, offshore platforms are influenced by factors such as wind, waves, and currents, as well as their interactions, leading to complex motion phenomena that affect the safety of offshore platform operations. Consequently, accurately predicting the motion response of offshore platforms has long been a key focus in the fields of naval architecture and ocean engineering. This paper utilizes STAR-CCM+ to simulate time-history data of offshore platform motion responses under both regular and irregular waves. Furthermore, a predictive model combining residual convolutional neural networks and long short-term memory neural networks using neural network technology is also studied. This model utilizes an autoregressive approach to predict the motion responses of offshore platforms, with its predictive accuracy validated through comprehensive evaluations. Under regular wave conditions, the coefficient of determination (R2) for the platform's heave and pitch responses consistently exceeds 0.99. Meanwhile, under irregular wave conditions, the R2 values remain generally above 0.4. Additionally, the model exhibits commendable performance in terms of Mean Squared Error (MSE) and Mean Absolute Percentage Error (MAPE) metrics. The aim of this study is to present a novel approach to predicting offshore platform motion responses, while providing a more scientific basis for decision-making in offshore platform operations. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Shanghai Jiaotong University (Science) is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The integrated development of offshore platform and net cage is a significant concern in ocean engineering. To optimize cost-effectiveness and maximize the utilization of limited ocean space resources, a composite structure is proposed, which integrates a submersible net cage onto the steel pipe piles of offshore platform. Based on the OpenFOAM software package, a numerical model is developed to assess the hydrodynamic performance of this composite structure. In this model, the net cage is simplified as a closed box structure comprising six planar nets, with each planar net further represented as a porous structure based on equivalent resistance. The model is validated by comparing the predicted results with the relevant experimental and numerical data. Subsequently, the model is employed to comprehensively investigate the hydrodynamic performance of the submersible net cage integrated with an offshore platform. Velocity variations inside and outside the net cage are analyzed under various wave-current conditions. Additionally, the forces exerted on the steel pipe piles by the net cage at different submerged depths are also examined. [ABSTRACT FROM AUTHOR]

Globally, aging offshore oil and gas (O&G) platforms face resource depletion, and regulations often demand platform removal through decommissioning. In the North Sea, >€90 billion will be needed for decommissioning by 2060. However, the influence of O&G platforms on fish communities is poorly understood. This challenges predictions of possible fisheries scenarios associated with different decommissioning options. Here, we examined the role that North Sea platforms played on fish communities. We explored patterns of fish abundance and body size variation along transects from O&G platforms comparing catch per unit effort data. Fish abundance was positively associated with O&G platforms. Atlantic cod, plaice, saithe, and mackerel were most abundant near platforms. Similarly, larger Atlantic cod were near the O&G platforms. Our study provided information for decision‐making regarding platform decommissioning scenarios by evidencing O&G platform habitat provisioning for various commercial fish species. [ABSTRACT FROM AUTHOR]

AbstractCurrent study presents state of the art approach to risk and reliability assessment for multivariate nonlinear dynamic systems. Specifically, novel hypersurface Gaidai risks evaluation methodology has been presented for evaluating offshore structural risks. Advocated approach being particularly suitable for offshore engineering multidimensional dynamic systems, possessing large number of critical components, that have either been physically observed/measured, or numerically modeled over a representative timelapse. Advocated Gaidai hypersurface structural risks evaluation methodology is applicable for a wide range of engineering and industrial systems. This study demonstrates that given in situ environmental conditions, it is well possible to assess accurately risks of system’s failures, damages or hazards, caused by excessive structural dynamics. Multivariate dynamic systems, possessing nonlinear cross-correlations between critical system’s components often present design challenges, when utilizing classic structural risks evaluation approaches, as those are mostly only univariate or bivariate. Dynamic offshore Jacket hot spot stresses have been utilized as an example in this reliability investigation. Modeling system’s excessive dynamics is challenging because of the non-stationarity of the system and the intricacy of fluid-structural dynamic interactions, arising from in situ wave-induced loads, influencing Jacket’s structural dynamics. Nonlinearities greatly affect structural dynamics, e.g., 2nd, 3rd, higher order effects within fluid-structural interactions. Methodology presented in this work offers a straightforward, effective, yet precise means of assessing the risks of failure or hazard for multivariate, non-stationary, non-linear dynamic offshore systems. For bivariate case, verification note has been added. [ABSTRACT FROM AUTHOR]

As a typical coating material for fire protection and heat insulation of offshore platforms, the intumescent fireproof coating can slow down the flame and heat propagation rate, thus it can gain time for fire fighting and personnel escape. However, the effective implement of the intumescent fireproof coating is subject to the quality control of the fireproof coating during the construction process. Therefore, this article systematically describes the key points and requirements of quality control in the construction process of intumescent fireproof coating on offshore platforms so as to provide reference for the construction quality control of fireproof coating in the field of marine engineering. [ABSTRACT FROM AUTHOR]

Several offshore platforms operating in the Java Sea have reported experiencing scour at varying depths, raising concerns about the safety and integrity of these structures. Scouring, an erosion phenomenon that occurs around these offshore platform structures due to their presence, is one of the most common issues encountered. The presence of scour can have a significant impact on the safety of these structures. To comprehend the implications of scour on structural safety, sensitivity analysis proves to be an invaluable tool. Sensitivity analysis establishes a relationship between changes in the safety parameters of the structure, obtained through linear analysis, and the depth of scour. By investigating this connection, sensitivity curves can be generated, enabling a conservative prediction of alterations in the strength parameters of the structure due to scour. In this study, a four-legged jacket platform structure underwent linear analysis under storm and seismic conditions using the SACS software. The scour phenomenon was simulated by adjusting the mudline's elevation beneath the structure, modifying the pile coordinates, reducing the length of piles beneath the mudline, and accounting for soil characteristics at each scour depth in the model. The sensitivity analysis revealed that the safety factors of the upper structural components, connections, and piles decrease at varying rates corresponding to each component type as the scour depth of the platform increases. By implementing these sensitivity curves, engineers and operators can make informed decisions regarding the maintenance and retrofitting of offshore platform structures to ensure their ongoing safety and structural integrity in the face of scour-related challenges. This research provides valuable insights into the critical relationship between scour depth and structural safety, enhancing our ability to protect offshore operations in the Java Sea and similar environments.

Leg mating units (LMU), consisting of steels and hyperelastic materials, are utilized to protect the structures during offshore platform float-over installation. Initial LMU design usually does not satisfy required performance since it is geometrically adjusted to fit given requirements based on previous design. To meet design criteria, design optimization can be applied to the initial design. However, a direct implementation of an accurate local search algorithm may cause heavy computations with the risk of falling into a local optimum. It can be also challenging to find an accurate optimum with efficient global search algorithms due to the characteristics of LMU problems. A small perturbation in nonlinear material can have a significant impact on LMU performance. Therefore, in this research, to find an optimum LMU design efficiently and accurately, an optimization framework that combines global and local search algorithms is implemented. In the framework, an efficient meta-model of optimal prognosis based evolutionary algorithm is first applied. The optimal design obtained from the first step, premature but near the optimum, is set as a new starting point for the sequential optimization where accurate polynomial based local adaptive response surface method is utilized. The robustness of the proposed framework is shown by the development of an LMU suitable for float-over installation of a 20,000-ton topside over an eight-legged fixed offshore jacket platform. [ABSTRACT FROM AUTHOR]

The real-time dynamic deformation monitoring of offshore platforms under environmental excitation is crucial to their safe operation. Although Global Navigation Satellite System-Precise Point Positioning (GNSS-PPP) has been considered for this purpose, its monitoring accuracy is relatively low. Moreover, the influence of background noise on the dynamic monitoring accuracy of GNSS-PPP remains unclear. Hence, it is imperative to further validate the feasibility of GNSS-PPP for deformation monitoring of offshore platforms. To address these concerns, vibration table tests with different amplitudes and frequencies are conducted. The results demonstrate that GNSS-PPP can effectively monitor horizontal vibration displacement as low as ±30 mm, which is consistent with GNSS-RTK. Furthermore, the spectral characteristic of background noise in GNSS-PPP is similar to that of GNSS-RTK(Real Time Kinematic). Building on this observation, an improved Complete Ensemble Empirical Mode Decomposition with Adaptive Noise (CEEMDAN) has been proposed to de-noise the data and enhance the dynamic monitoring accuracy of GNSS-PPP. Field monitoring application research is also undertaken, successfully extracting and analyzing the dynamic deformation of an offshore platform structure under environmental excitation using GNSS-PPP monitoring in conjunction with improved CEEMDAN de-noising. By comparing the de-noised dynamic deformation trajectories of the offshore platform during different periods, it is observed that the platform exhibits reversible alternating vibration responses under environmental excitation, with more pronounced displacement deformation in the direction of load action. The research results confirm the feasibility and potential of GNSS-PPP for dynamic deformation monitoring of offshore platforms. [ABSTRACT FROM AUTHOR]

Offshore platforms are vulnerable to fire accidents and it is essential to conduct safety analysis in case of an evacuation and take measures to improve worker evacuation efficiency and reduce casualties. Based on the proposed Credible and Representative Fire Scenarios (CRFS) methodology, nine fire scenarios were selected and simulated. The safety analysis of fire evacuation was performed based on the coupled injury model and the modified social force model, while the effects of wind direction, wind speed, fire location and pre-evacuation time on the probability of death (POD) were investigated. The results demonstrated that the wind from the stern led to a higher coverage rate of smoke (CRS) on the decks and higher POD values. The wind from the bow, larboard and starboard sides was shown to be more conducive to the dissipation of smoke. As a result, the overall POD values were relatively low. The magnitude of wind speed affects the accumulation behavior of smoke between different decks, and the lower the wind speed, the higher the CRS on the decks and POD of the workers.The pool fire located on the lower deck was more likely to cause injuries than the fire on the working deck. In addition, it was found that the trend between POD and pre-evacuation time shows a non-linear relationship, thus the scenario with the most severe fire threat was used as an example for regression analysis. An approach was proposed to determine the fire-evacuation safety time windows in the event of a fire accident and the time windows in different areas of the nine selected scenarios were predicted. Finally, the time windows obtained from the regression curves and the proposed method were compared. [ABSTRACT FROM AUTHOR]

In the random sea environment, offshore platforms are influenced by factors such as wind, waves, and currents, as well as their interactions, leading to complex motion phenomena that affect the safety of offshore platform operations. Consequently, accurately predicting the motion response of offshore platforms has long been a key focus in the fields of naval architecture and ocean engineering. This paper utilizes STAR-CCM+ to simulate time-history data of offshore platform motion responses under both regular and irregular waves. Furthermore, a predictive model combining residual convolutional neural networks and long short-term memory neural networks using neural network technology is also studied. This model utilizes an autoregressive approach to predict the motion responses of offshore platforms, with its predictive accuracy validated through comprehensive evaluations. Under regular wave conditions, the coefficient of determination (R2) for the platform’s heave and pitch responses consistently exceeds 0.99. Meanwhile, under irregular wave conditions, the R2 values remain generally above 0.4. Additionally, the model exhibits commendable performance in terms of Mean Squared Error (MSE) and Mean Absolute Percentage Error (MAPE) metrics. The aim of this study is to present a novel approach to predicting offshore platform motion responses, while providing a more scientific basis for decision-making in offshore platform operations.

In the course of towing of offshore platform, it is of great significance to calculate the towing resistance ahead of time and select the main tugboat with proper power for towing safety. In this paper, the calculation formulas or recommended methods for towing resistance of mainstream classification societies were investigated, and a CFD/AQWA finite element numerical simulation was conducted for the typical jack-up offshore platform in Shengli Petroleum Engineering Company.Based on the comparative analysis of the results, a suitable model for the calculation of towing resistance of platforms in domestic waters was optimized, and a suitable towing factor of safety was proposed.

Objective The aim is to solve the problem that a triethylene glycol(TEG) dehydration unit on an offshore platform could not meet the dehydration requirements. Methods Based on the actual production data, the simulation analysis of the process system was carried out by HYSYS software to found out the causes of the operation problems of the system. Results The high water content in the natural gas at the inlet of the dehydration tower is the main factor affecting the effect of the dehydration system. Both the inlet filter separator and the reboiler should be considered in the transformation plan. Combined with the actual situation of the platform, the transformation scheme was finally determined to replace the inlet filter separator filter element and the electric heater of reboiler. After the transformation, the dew point of dry gas water at gauge pressure of 5.2 MPa was reduced from 6 ℃ to -23 ℃ which achieved the expected effect and reserved the operation space for subsequent expansion. Conclusions The reason why the processing capacity of the TEG dehydration unit on the offshore platform cannot reach the design value might be that the performance of the inlet filter separator was not up to standard, which leads to the excessive water content of the natural gas at the inlet of the dehydration tower. It was suggested that the processing index of the inlet filter separator should be strictly controlled during the process design of the TEG dehydration unit, and the TEG dehydration device should be matched according to the treatment index of the inlet filter separator. [ABSTRACT FROM AUTHOR]

Copyright of Metal Working (1674-165X) is the property of Metal Working Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This article presents a robust methodology for long-term offshore structural health monitoring (SHM) using the Global Navigation Satellite Systems (GNSS). The methodology relies on recently developed regional reference frames and single-receiver phase-ambiguity-fixed Precise Point Positioning techniques. The stable Gulf of Mexico Reference Frame 2020 (GOM20) provides a robust and consistent reference system for long-term offshore SHM in the Gulf of Mexico (GOM). Continuous GNSS observations (DEV1, 2010–2020) on a fixed platform in the Eugene Island 330 oil field are used to illustrate the methodology. The platform was installed in 1982 in 82-m water about 130 km away from the Mississippi Delta coastline. The major monitoring items include horizontal movements, seafloor subsidence, structure submergence, and seasonal oscillations. The stand-alone GNSS monitoring achieves 3- to 4-mm root-mean-square accuracy in the horizontal direction and 7 mm in the vertical direction for daily positions in the GOM region. According to this study, the GNSS antenna (DEV1) has moved 6 cm toward the northeast with respect to GOM20 since 2010; the ongoing structure submergence rate in the Eugene Island 330 oil field area is approximately 15 mm/year, a combination of seafloor subsidence (12 mm/year) and sea-level rise (2.6 mm/year) with respect to GOM20. The submergence in the future 40 years (2021–2060) would be greater than 0.6 m, likely between 0.8 and 1.0 m, but is unlikely to exceed 1.3 m. The peak-to-trough amplitudes of the seasonal movements at the top of the platform are below 5 mm in all three directions, comparable with the seasonal movements recorded by onshore GNSS in the Louisiana coastal region. The methodology introduced in this article can be applied to SHM in other offshore regions where stable regional reference frames are available. [ABSTRACT FROM AUTHOR]

Under the background of rapid digital transformation in the oil industry, in order to improve the development efficiency of offshore platform simulation system, this paper proposes a simulation method of offshore platform based on virtual reality technology. This method completes the rendering and output of the screen by using a physics based rendering framework; Develop adaptive tools to produce a large amount of repetitive content such as sensor range and handrail; The external general file driven editing mode, such as Excel, allows users to directly modify some information. The actual project application shows that the above methods can reduce more than 90% of the screen rendering time, improve the production and modification efficiency of repetitive work, and improve the flexibility and robustness of the system. This method provides reference for the subsequent simulation project production and helps the digital construction of offshore oil. [ABSTRACT FROM AUTHOR]

Structural health monitoring (SHM) is crucial for ensuring the safety and performance of offshore platforms. SHM uses advanced sensor systems to detect and respond to negative changes in structures, improving their reliability and extending their life cycle. Model updating methods are also useful for sensitivity analysis. It is feasible to discuss and introduce established techniques for detecting damage in structures by utilizing their mode shapes. In this research, by considering reducing the stiffness of elements in the damage scenarios, we conducted simulations of the models in MATLAB, including both two-dimensional and three-dimensional structures, to update the method suggested by Wang. Wang’s method was improved to produce a sensitivity equation for the damaged structures. The sensitivity equation solution using a subset of mode shapes data was found to evaluate structural parameter changes. Comparing the updated results for Wang’s method and the suggested method in the two- and three-dimensional frames showed a noticeable modification in damage recognition. Furthermore, the suggested method can update a model containing measurement errors. Since Wang’s damage detection formulation is suitable only for 2D structures, this modified framework provides a more accurate decision-making tool for damage detection of structures, regardless of whether a 2D or 3D formulation is used.

Operators of offshore production units (OPUs) employ risk-based assessment (RBA) techniques in order to minimise inspection expenses while maintaining risks at an acceptable level. However, when human divers and workers are involved in inspections conducted at high heights, the operational risks can be significant. Recently, there has been a growing trend towards the use of unmanned aerial vehicles (UAVs), autonomous surface vehicles (ASVs), remotely operated vehicles (ROVs), and autonomous underwater vehicles (AUVs) for inspections of offshore structures as a means to reduce exposure to human risk. This article provides an analysis of these vehicle inspection capabilities and their potential to enhance robustness and safety within the oil and gas industry. The review assesses both the advantages and the drawbacks associated with these innovative systems, providing valuable comparisons and assessments on their potential use as viable alternatives to conventional inspection methods. [ABSTRACT FROM AUTHOR]

Aimed at the operating failure problem of a shaft end mechanical seal of the oil-gas multiphase pump on the offshore platform, the causes were analyzed, and the structure was improved. Through the performance test of the improved mechanical seal, the change of sealing performance with pressure the wear condition of sealing end face under different spring specific pressure conditions were compared and analyzed, and the change of sealing performance with pressure and rotational speed under different end face widths was compared and analyzed. The results show that reducing the spring specific pressure can slightly reduce the friction power of the seal end face, but it will increase the risk of leakage, and reducing the end face width can effectively improve the sealing performance under poor lubrication conditions. The optimal design parameters of the seal were determined, and the 100 h qualification test of the domestic sealing prototype was carried out. The stability of the friction power of the sealing end face and the leakage index during its operation were examined. The experimental results show that the friction power of the improved sealing end face is basically stable, with small fluctuations, and the leakage meets the standard index requirements. This verifies the rationality of the improved sealing structure, the effectiveness and the adaptability of operating conditions of optimizing design parameters. [ABSTRACT FROM AUTHOR]

The primary objective of this study was to assess differential vertical and horizontal deformations for the offshore Kashagan oilfield located in the Northern Caspian Sea. Sentinel-1 (SNT1) and COSMO-SkyMed (CSK) synthetic-aperture radar (SAR) images (9 January 2018–6 April 2022) were processed using persistent scatterer interferometric SAR (PS-InSAR) technique with further 2D decomposition of line-of-sight (LOS) measurements to differential vertical and horizontal deformations. Differential vertical deformation velocity was observed to be between −4 mm/y and 4 mm/y, whereas horizontal was between −4 mm/y and 5 mm/y during 2018–2022. However, it was possible to observe the spatial deformation patterns with the subsidence hotspots reaching differential cumulative vertical displacement of −20 mm from both satellite missions. PS-InSAR differential vertical deformation measurements derived from SNT1 and CSK satellite images showed identical spatial patterns with moderate agreement, whereas poor agreement was observed for differential horizontal deformations. The differential vertical deformation hotspots were observed for the oilfield areas installed on piles with obviously higher vulnerability to dynamic movements. Through this study, based on the interferometric measurements, marine geotechnical expert feedback, and no reported deformation-related incidents since 2013, it was possible to conclude that the Kashagan oilfield had not been impacted by significant differential vertical and horizontal deformations on the oilfield. However, since long-term GPS measurements were not accessible from the oilfield to be used as the reference for PS-InSAR measurements, we were not able to judge the long-term displacements of the entire oilfield or possible oscillations, even though it is built on the artificial island. Considering the broad range of PS-InSAR measurements using time-series radar images, the interferometric measurements could play a significant role in the prioritization of insitu risk assessment activities, operational cost reduction, strengthening of safety factors, and planning of further targeted insitu measurements. [ABSTRACT FROM AUTHOR]

Large‐scale pool fires on offshore platforms can have disastrous consequences. Wind load is an essential component of the marine environment; hence, wind‐shielding facilities are installed on the platforms as needed. A computational fluid dynamics technique is used in this study to model large‐scale pool fires. The effects of wind load and windshields on large‐scale pool fires are investigated. Furthermore, the impact of the large‐scale pool fire on personnel is evaluated based on thermal radiation dose. It has been discovered that the growing horizontal momentum of the wind load might result in a significant distance of fatal injury. The windshields have double‐edged effects, including that: (1) they can reduce the injury distance by preventing the spread of fire products; and (2) they could block the release of heat and smoke. It is advised that while installing windshields on offshore platforms, different fire scenarios need to be considered. This research can be used to provide technical support for the development of the emergency evacuation strategy and layout design of offshore platforms. [ABSTRACT FROM AUTHOR]

ObjectiveA string-type mooring system is proposed for the permanent berthing demands of special offshore platforms. So it is necessary to study the hydrodynamic performance of the berthing platform using this mooring system to verify its adaptability to the permanent berthing demands.MethodsBased on the three-dimensional potential flow theory, a numerical model of the platform berthed alongside a terminal wharf is established using the boundary element method, and the frequency domain numerical simulation of the moored platform at different tide levels is carried out. Two mooring systems, i.e., string-type and traditional dock mooring, are used to simulate the hydrodynamic performance of the platform in the time domain under extreme wave conditions, and parameterized analysis is conducted to analyze the influence of different tide levels on the motion response of the platform.ResultsBy providing omni-directional restoring force, the string-type mooring system strengthens the rotational motion limitations of the platform, greatly reduce the most violent rolling motion, transfers the energy of environmental load to translational motion, and further strengthens the restriction of the overall motion of the platform; the motion range of the platform is balanced, stable and controllable; and the effects of the system on the motion limit of the platform are less affected by the change in tide level.ConclusionCompared with the traditional mooring system, the string-type mooring system is more suitable for the permanent berthing of special offshore platforms.

Using the crude oil ultrasonic treatment experimental device, the effects of ultrasonic action time, action temperature, ultrasonic frequency, ultrasonic power, and crude oil viscosity changes on the viscosity reduction characteristics are analyzed. The results show that when the temperature is lower than 70 °C, the viscosity of crude oil is significantly reduced by ultrasonic treatment. When the temperature is higher than 70 °C, the viscosity of crude oil after ultrasonic treatment increases, mainly due to the effect of the cavitation threshold. With the increase of ultrasonic action time, the viscosity reduction of crude oil after ultrasonic treatment increases first and then decreases, which is mainly related to the thermal effect of ultrasound. When the ultrasonic power increases, the time required to achieve the same ultrasonic cavitation effect becomes shorter, and the optimal ultrasonic action time becomes shorter. With the increase of ultrasonic power, ultrasonic viscosity reduction first increases and then decreases, and there is a critical optimal ultrasonic power. The viscosity reduction effect of ultrasonic treatment is better for crude oil with viscosity ranging from 500 mPa ⋅ s to 1 081 mPa ⋅ s at 50 °C. [ABSTRACT FROM AUTHOR]

The increase of Renewable Energy (RE) production to fight the climate crisis is posing new technological and financial challenges, due to the availability and variability of RE Sources (RES). These challenges can be addressed by selecting the most suitable mix of RES to optimise power production, to assure grid resilience and to promote local energy use. To facilitate the selection of such combination, this paper presents an original methodology that allows to compare mixing scenarios with different RES, also in presence of batteries and backup system. It simultaneously optimises the energy surplus with respect to the eventual external electrical load and the missing energy with respect to the same electrical load. This method, which can cope with isolated or plugged-to-grid systems, is here applied to a novel case study, an oil&gas platform under decommissioning, located in the Adriatic Sea (Italy). The RE production from wind, wave and solar panels is supposed to support other activities for the platform reuse, such as aquaculture, monitoring and mineral deposition. In this case, solar energy is providing the greatest contribution to the optimal mix in terms of production, while wave energy assures the most relevant contribution in terms of continuity. [ABSTRACT FROM AUTHOR]

The decommissioning of offshore platforms has been increasingly discussed due to its economic, social, and environmental impacts. The high complexity of this multilevel context pushes for the adoption of a service ecosystem view to explore the value propositions and actors' relations involved in resource exchanges. This study follows a mixed‐method approach based on semistructured interviews conducted with oil and gas stakeholders and content analysis of the secondary data collected. The results highlight the ecosystem elements and identify the main drivers for sustainable growth in the process of the reconversion of oil and gas assets. A "meta" level is theorized to investigate how the actors' purposes can be harmonized with an ecosystem's goal to encourage the diffusion of a sustainable‐oriented culture in the context of offshore decommissioning. In this sense, the study provides several insights for researchers and professionals in both the local and national governance field and the oil and gas industry. [ABSTRACT FROM AUTHOR]

The efficiency of a tuned liquid damper (TLD) in controlling the dynamic responses of offshore monopile platforms under seismic excitation has been investigated in this paper. Damping is performed by applying a type of reservoir inside a tower, which is designed optimally via seawater and a monopile body. Hydrodynamic forces due to water surface oscillation in the reservoir act as resistant forces against structure vibration and displacement. Using ANSYS finite element (FE) software, a monopile structure with the same dimensions as the samples in the Persian Gulf climate was modeled and then analyzed in this research using the transient time history analysis related to the records of El-Centro, Kobe, and Tabas earthquakes for seismic investigation. The dynamic responses of the monopile platform with and without TLD were compared after the completion of FE results. Findings show that using the mentioned TLDs reduced structure displacement by more than 50% based on the earthquake frequency content. [ABSTRACT FROM AUTHOR]

Structural health monitoring (SHM) is crucial for ensuring the safety and performance of offshore platforms. SHM uses advanced sensor systems to detect and respond to negative changes in structures, improving their reliability and extending their life cycle. Model updating methods are also useful for sensitivity analysis. It is feasible to discuss and introduce established techniques for detecting damage in structures by utilizing their mode shapes. In this research, by considering reducing the stiffness of elements in the damage scenarios, we conducted simulations of the models in MATLAB, including both two-dimensional and three-dimensional structures, to update the method suggested by Wang. Wang's method was improved to produce a sensitivity equation for the damaged structures. The sensitivity equation solution using a subset of mode shapes data was found to evaluate structural parameter changes. Comparing the updated results for Wang's method and the suggested method in the two- and three-dimensional frames showed a noticeable modification in damage recognition. Furthermore, the suggested method can update a model containing measurement errors. Since Wang's damage detection formulation is suitable only for 2D structures, this modified framework provides a more accurate decision-making tool for damage detection of structures, regardless of whether a 2D or 3D formulation is used. [ABSTRACT FROM AUTHOR]

Fixed marine structures is widely utilized as production or oil recovering platform in the shallow sea, and are also subject to random loading. Jacket structures subject to random loading pose difficulties in both analysis and design, with solutions commonly only viably acquired employing a numerical technique. Performance of offshore jacket platforms is highly related to configuration of the braces. In this regard, probabilistic scheme is a good option for evaluating jacket structures. In this paper, the performance of Resalat jacket structure located in the Persian Gulf with different kinds of bracing configuration is investigated. We present a new measuring index for optimum arrangement of bracing configuration which is defined as probabilistic design criterion. The Latin Hypercube Sampling (LHS) method, which is a more advanced and appropriate form of the Monte Carlo simulation technique, is used to investigate different configurations. Hereof, probabilistic analysis is performed on different configurations of platform structure using the LHS method. The elastic modulus is employed as the random input variable for probabilistic analysis, and the maximum values of stress and horizontal displacement are selected as the random output variables. Also, at the end of the calculations, the optimum configuration can be found. It is demonstrated that the proposed probabilistic optimization algorithm is capable of effectively determining the optimum configuration of jacket platform structures. Therefore, an optimum bracing configuration can be useful in evaluating and designing the fixed marine structures.

DC microgrids present a very effective solution that enables the power systems of offshore platforms to achieve increased integration of renewable sources. Since the areas of offshore platforms are limited, the associated DC microgrids have lower line impedances, and short-circuit faults cause fault currents to rise rapidly. Thus, fault detection is a challenging issue due to the strict time limits for interruption imposed by these rapid rising fault currents. According to the fault characteristics and the ring structure of DC microgrids, this paper proposes a rapid detection scheme based on the differential current and current derivative without de-energizing the entire DC microgrid. It achieves rapid and selective fault detection and ensures an uninterruptible load power. The synchronization issues of the current differential and a rapid processing method for fault currents are investigated. The tripping threshold settings are discussed. Implementation of the fault detection scheme is also presented in detail. The proposed scheme is verified on a physical experimental platform. It is shown that here are some advantages such as good selectivity, low cost, and rapid fault detection. The scheme provides a strong guarantee for the uninterruptible operation of important equipment on offshore platforms. [ABSTRACT FROM AUTHOR]

Recently, the NORSOK standards, which regulate noise and vibration on offshore platforms, were strengthened by prohibiting the use of glass wool for environmental and safety reasons. In addition, the use of sound-absorbing materials in panels and silencers was prohibited. Therefore, developing a silencer that does not use sound-absorbing materials is necessary. In this study, a bandgap expressed by acoustic characteristics of a periodic structure was applied to develop a silencer without sound-absorbing materials. The bandgap is formed in a frequency range in which propagation of acoustic waves is suppressed by setting a specific distance between single units based on periodic structural theory. The designed silencer evaluates the noise attenuation effect of the periodic structure based on a fluid-structure coupling finite-element equation for a plane wave in a stationary medium. In addition, the silencer model was selected by analyzing the regenerated noise originating from the periodic structure in the flow duct. This flow noise is used to analyze the propagation of sound waves based on the FW-H equation. This is achieved by employing the Lighthill acoustic analogy to predict the flow-induced sound pressure. Furthermore, compressed air was injected at the end of the duct in the flow noise experiment to perform measurements. The results from the acoustic and flow noise experiments were compared to confirm the effect of the flow in the duct on noise generation. Moreover, the flow noise analysis based on the flow velocity elucidated the effect of the periodic structure on the flow. In addition, the analysis results were used to investigate its performance of the silencer with the periodic rod arrangement considering the flow noise in the duct and predict its acoustic characteristics in the bandgap frequency range. [ABSTRACT FROM AUTHOR]

Vibration sensing is of great significance in offshore engineering monitoring and safety detection. This paper presented a low-frequency vibration sensor (LV-TENG) based on a cantilever-beam-structured triboelectric nanogenerator, which can perform high-precision vibration sensing while conducting vibration energy collection effectively. The LV-TENG was composed of two aluminum electrode layers, a spring steel sheet covered with polytetrafluoroethylene (PTFE) and a first-order vibration mode structured frame. Under the excitation of external vibration, the spring steel sheet undergoes first-order modal vibrations between the aluminum electrodes and generates a periodically fluctuating electrical signal in the external circuit. The vibration profile of the cantilever beam was first analyzed theoretically to provide guidance for structural design. On this basis, the influence of the main structural parameters, including the structure of the Al electrode, the thickness of the steel plate, and the electronegative materials, on the output performance of LV-TENG was experimentally investigated and the structure was optimized to enhance electrical output. The results showed that the LV-TENG can accurately sense structure vibration with a frequency of 0.1 Hz to 5.0 Hz and an amplitude of 2.0 mm to 10.0 mm. The measured output voltage followed a positive linear relationship with frequency and the fitted correlation coefficient reached 0.994. The demonstration experiment indicated that the LV-TENG is expected to provide a new avenue for low-frequency vibration monitoring and can be used for structural health monitoring analysis in marine engineering. [ABSTRACT FROM AUTHOR]