Search

Existing devices available on offshore gas/oil platforms are incapable of realizing complete separation of the liquid phase from wet natural gas. This results in eccentric motion of rotors and eventually causes trouble halting of natural-gas compressors. To tackle this problem, use of a novel gas-liquid separator has been reported for offshore oil platform applications. A pilot scale test was performed using the proposed equipment. Results of the test demonstrate that the optimum operating point of the pilot plant corresponds to a flow rate of 90 m3/h (30 °C, 5.0 MPa), and this could be used as a reference for subsequent industrial scale-ups. The results of the pilot test lead to the conclusion that the said novel separator has higher separation efficiency when compared against conventional industrial devices used on oil platforms. Using of the proposed equipment is aimed at alleviating the problem of liquid entrainment of natural gas entering the compressor, increasing compressor service life, and reducing operational and maintenance costs. The proposed study provides a new outlook towards engineering design of offshore-oil-platform equipment of theoretical as well as practical value. • Use of a novel gas–liquid separator to separate the liquid phase from natural gas extracted from the seafloor is proposed. • Operating conditions during the pilot test were maintained identical to those corresponding to industrial operation. • An improvement in separation efficiency was achieved over conventional separators employing cyclone and wire-mesh demisters. • The service life of compressors will be improved. [ABSTRACT FROM AUTHOR]

Steel tubular structures are widely used in the construction of offshore platforms and T-type junctions are extensively used in this domain. The tubular members are welded, which generates significant stress concentrations at the edges. The stress levels reached in these critical places are used to assess lifetimes based on fatigue curves from tests conducted on standard samples. This study is devoted to the modeling and analysis of T-type welded tubular structures for the determination of hot spots stresses (HSS) at the chord/brace intersection, A numerical analysis was carried out to study the effect of a combined loading composed of an axial loading and a continuation of rational bending, that best assimilate real conditions, as well as the effect of normalized geometric parameters a, ß, on the distribution of stress concentration (area and values) of T-joints. The mechanical behaviour has been modeled in 2D using quadrangular and triangular thin-shell elements by the finite element method (FEM). It is the most appropriate approach because it considers all geometric complexities and singularities of the structure, while the efforts as well as the computation time are considerably reduced compared to an experimental study or to complex FE models implementing solid elements. In this study, we use the COMSOL-MULTIPHYSICS® software. [ABSTRACT FROM AUTHOR]

Recent advances in deep learning for automatic target recognition have inspired studies for maritime surveillance with synthetic aperture radar (SAR). In this context, oil rigs monitoring is of particular interest. There are offshore platforms of different types and sizes which poses challenges for classification methods. In this letter, we compare the recognition of oil rigs on Sentinel-1 SAR images, discriminating them from false alarms, through a convolutional neural network with a different number of layers named models VGG-16 and VGG-19. We used the Sentinel-1 GRD product, which has a resolution of about 20 m, with VV and VH channel image data sets separated to observe polarization influences on target recognition. The experiments show that the VH polarization image embedding contributes with the best classification values, with the mean global accuracy of fifty random sampling tests equal to 86.4% and 84.1% using the VGG-16 and VGG-19 architectures, respectively, to extract features and feed a logistic regression classifier method. Results suggest that these approaches are a useful alternative for maritime surveillance employing SAR images of medium resolution and large swaths. Furthermore, the database balancing for wind conditions did not provide significant contributions to the accuracy of classification algorithms. [ABSTRACT FROM AUTHOR]

The structural damage identification, which entails finding a best approximate solution to an over-determined system of linear equations, is actually one of the practical problems encountered in structural health monitoring. A major challenge to structural damage identification is the ill-conditioned problem caused by noise contamination and spatially incomplete measurements. A novel Tikhonov regularization iterative method (TRIM) is proposed to solve the ill-conditioned system of linear equations. This method iteratively reconstructs the regularization matrix by gradually updating the regularized solution. A merit is that the false-positive indicators of damage are greatly reduced; and as a result this approach would be able to detect smaller damages that could not be detected by using traditional approaches. Another development embedded in TRIM is that a procedure, called singular value dichotomy, is developed to determine the regularization parameters. Several problems, such as the tremendous prior trials, due to the application of L-curve, are avoided. A numerical study is conducted on an offshore platform structure to demonstrate the effectiveness of the proposed method. The result shows that the new method outperforms the traditional Tikhonov regularization method in damage identification. [ABSTRACT FROM AUTHOR]

A modified multiple generalized regression neural network (GRNN) is proposed to predict the noise level of various compartments onboard of the offshore platform. With limited samples available during the initial design stage, GRNN can cause errors when it maps the available inputs to sound pressure level for the entire offshore platform. To obtain more relevant group for GRNNs training, fuzzy C-mean (FCM) is used. However, outliers in some group may interfere the prediction accuracy. The problem of selecting suitable inputs parameters (in each cluster) is often impeded by lack of accurate information. Principal component analysis (PCA) is used to ensure high relevance input variables in each cluster. By fusing multiple GRNNs by an optimal spread parameter, the proposed modeling scheme becomes quite effective for modeling multiple frequency-dependent data set (ranging from 125 to 8000 Hz) with different input parameters. The performance of FCM-PCA-GRNNs has improved significantly as the results show a 25% improvement on the spatial sound pressure level (SPL) and 85% improvement on the spatial average SPL than just GRNNs alone. By comparing with data obtained from real engine room on a jack-up rig, the FCM-PCA-GRNNs noise model performs better with around 16% less error than the empirical-based acoustic models. Additionally, the results show comparable performance to statistical energy analysis that requires more time and resources to solve during the early stage of the offshore platform design. [ABSTRACT FROM AUTHOR]

This paper deals with the assessment of fatigue crack propagation on the connection between column and brace for a semi-submersible. The analysis of global and local structural responses under different sea states are performed to acquire the transfer functions of stresses. Based on an existing crack the Failure Assessment Diagrams (FAD) are applied as criterion of acceptance for the safety of crack and structure during the crack growth calculation cycle. The crack growth rate considering threshold stress intensity factor and stress ratio is used. During safety assessment the stress response from ultimate sea state is outlined. A comparison of fatigue crack growth using ultimate stress and normal stress data with different crack growth rate is presented. The results show the reliability of fatigue assessment using FAD as a measurement of acceptability of crack propagation. [ABSTRACT FROM AUTHOR]

Highlights • Topology optimization method is presented for offshore jacket platform design. • Environmental loads are analyzed for the offshore jacket platform. • Clear jacket structure is obtained through a series of topology iterations. • Optimization results are verified by FE analysis for static and dynamic performance. Abstract Offshore jacket platform is widely used as production or oil recovering platform in the shallow sea, and is also applied to the offshore wind turbine supporting structure in the recent years. The jacket structures are normally designed to be conservative and bulky according to various design codes. In this work, a structural optimization design method for jacket platform structure has been developed based on topology optimization theory. The topology optimization method is applicable at an early design stage, which can determine the initial structure and force transmission path. The whole design space is chosen as design variables, and the goal is to maximize the structural stiffness. A set of constraints based on multi-criteria design assessment is applied according to standard requirements, which includes stress, deformation, vibration and design variable constraints. The optimization results are compared with the original platform for static performance, dynamic performance and Ultimate Carrying Capacity (UCC). Results show that the optimized structure show a 13.7% reduction in the global mass, 46.31% reduction in the maximum equivalent stress, and large ultimate carrying capacity ability under the same environmental loads. It is demonstrated that the proposed topology optimization method is capable of effectively determining the optimal design of jacket platform structures. [ABSTRACT FROM AUTHOR]

Abstract For steel jacket-type offshore platforms under irregular wave forces, we study the networked predictive vibration controller with inevitable random time delays, packet dropouts, disordering, and disturbance. First, we present a model of networked control system with two buffers, and the model is applied in the vibration control of offshore platforms. The buffers are designed to solve the above problems and located in the sensor-to-controller and controller-to-actuator channels of the networked control systems (NCSs). Second, we design networked predictive feedforward and feedback controller based on the received packets of past time. A new Algorithm is presented to simplify the computation of control law and reduce the storage required. Therefore the designed controller is physically realizable and easy to complete. Third, we made stability analysis of the controller by Lyapunov function. Finally, example of steel jacket-type offshore platform is applied to verify the feasibility and efficiency of controller. The simulation results show that the networked predictive vibration controller can compensate random big delays, large packet dropouts and disordering efficiently. Compared with different controllers, the presented predictive controller can decrease oscillation of offshore platform more significantly and the required control force can be kept in ideal small scale simultaneously. [ABSTRACT FROM AUTHOR]

Wave loading is one of the leading factors contributing to fatigue damage of offshore platforms. Vibrations in marine platforms due to nonlinear hydrodynamic forces can reduce platform productivity, endanger safety, and affect serviceability. This article presents numerical evaluation of a magnetorheological elastomer device for wave-induced vibration reduction of offshore platform. Random wave loadings are estimated by wave spectrum analysis and Morison's equations. By altering field-induced stiffness of magnetorheological elastomers and non-resonance control strategy, the wave-induced vibration of offshore platform is effectively reduced, and the magnetorheological elastomer device presents strong control robustness under various wave loadings. This work indicates that magnetorheological elastomer-base device may open a new insight for vibration mitigation of ocean structures. [ABSTRACT FROM AUTHOR]

Highlights • A novel spectral moments equivalence based lumping block method is developed. • A correction factor is introduced to improve the performance of the proposed method. • The effectiveness of the method is validated with numerical and experimental results. • The new method outperforms the conventional methods both in accuracy and robustness. Abstract This paper provides a novel lumping block equivalence method, termed as spectral moments equivalenc e (SME) based method, to improve the efficiency of fatigue assessment in preliminary design stage. In the newly SME method, an equivalent equation of representative sea state's spectral wave energy and original sea state's spectral wave energy is set up in the fatigue equivalence viewpoint. The relations of wave parameters and wave spectral moments are introduced into the SME method to determine the equivalent significant wave height and up-crossing wave period of the representative sea state. A key feature of the SME method is that the effect of S-N curve's slope and quantity of sea state in lumping block is incorporated into the equivalent formulae to make the method applicable to different lumping block partitions and fatigue curves. In addition, the SME method also has advantage of preserving the stochastic characteristics of sea states. Cumulative fatigue damage of fixed and floating offshore platforms are generated to verify the validity and applicability of the SME method. Numerical results indicate that the SME method not only yields the most accurate fatigue assessment but also has robustness to block partitions and offshore structures. [ABSTRACT FROM AUTHOR]

Highlights • Study of structure-borne sound transmission of cascaded plate–cavity system. • Application of Chebyshev-Ritz method. • Comparable numerical accuracy as compared to finite element method. • Numerical examples are simulated for different configurations. • Better prediction of sound transmission via tuning of cascaded plate–cavity system. Abstract A Chebyshev-Ritz based analytical model is proposed to investigate I-junction within the structural–acoustic model of a cascaded rectangular plate–cavity system. By considering of the structural interconnection force and the moment at edges and structural-acoustic interaction on the interface, the structural and acoustic systems are coupled. Two-dimensional and three-dimensional Chebyshev Polynomial series are used to present the unknown panel displacements and the sound pressure field variable inside the cavities, respectively. The effectiveness and correctness of the proposed model on an I-junction in a typical marine offshore platform are verified with those calculated from Finite Element Analysis. The influence of boundary conditions, structural coupling, plate properties, and size of the source-to-receiver cavities on the offshore platform on structure-borne sound transmission are analyzed and addressed. Numerical examples are simulated for several different configurations. It is shown that the boundary conditions, structural coupling manner, plate properties, and the volume ratio of the source-to-receiver cavity will change the structure-borne sound transmission characteristics of the cascaded rectangular plate–cavity system. With the proposed approach, a better prediction can be obtained for structure-borne sound transmission via proper tuning of the cascaded rectangular plate–cavity system on the offshore platform. [ABSTRACT FROM AUTHOR]

Considering the high sensitivity of the location accuracy of the threshold-based time difference of arrival (TDOA) location method to the threshold, a TDOA location method involving an acoustic emission (AE) source for offshore platform damage based on visible graph (VG) modelling was proposed. The corresponding network topology to AE time domain signals was constructed using visible graph modelling. Node degrees in the network were analysed and nodes with singular degrees were used as the time of arrival (TOA) of the corresponding waveform, thereby extracting the TOA of SO and AO mode waves. Experimental results demonstrated that the proposed TDOA location method can effectively avoid the impact of the threshold on the TOA and can improve the location accuracy and stability of the TDOA method. [ABSTRACT FROM AUTHOR]

Fossil fuel is not practically renewable and therefore the world is at risk of fossil fuel depletion. This gives urgency to investigate alternative energies, especially for industries that rely entirely on energies for operations, such as offshore industry. The use of alternative energies in this industry has been in place for a while now. This paper discusses the application of various alternative energy sources to assist powering the Goodwyn Alpha (A) Platform, located on the North West Shelf (NWS) of Australia. The three alternative energy sources under discussion are: wind, wave and solar. The extraction devices used are the Horizontal and Vertical-Axis Wind Turbines - for wind; Pelamis, PowerBuoy and Wave Dragon - for wave; and the solar parabolic dish of SunBeam and Photovoltaic (PV) cells of SunPower - for solar. These types of devices are installed within the same offshore platform area. Technical, environmental and economic aspects are taken into consideration before the best selection is made. The results showed that PowerBuoy used for wave energy, is the best device to be used on offshore platforms where operators could save up to 9% of power; $603,083 of natural gas; and 10,848 tonnes of CO2 per year.

Due to long-term used in the harsh environment,the functional degradation of the FPSO crane such as corrosion,fatigue crack,local failure occurred. The functional degradation could affect the normal use of the FPSO crane. According to the actual surveying data,the finite element model of the FPSO crane has been established by finite element software Ansys. The stress of high stress area has been tested according to the stress distribution of the FPSO crane. The calculation results of Ansys have been compared with the test data. The errors between calculation results and test data are in 14%,except of point 1941.The stress value of the most dangerous area is 247. 96 MPa,which is less than the allowable stress of the crane. Thus the strength requirement is satisfied. The relation between stress of key area of crane and the angle β of lifting has been analyzed. When the weight of lifting is close to the maximum working load,the working condition of β > 15°is preferred.

To improve the anti-explosion performance of blast wall in offshore platforms, an auxetic re-entrant blast wall (ARBW) was proposed and designed based on the indentation resistance effect of an auxetic structure. Based on the numerical nonlinear dynamic analysis method verified by the explosion experiment of a conventional steel corrugated blast wall (CBW), the failure mechanisms of ARBW, steel honeycomb sandwich blast wall (HSBW) and CBW were investigated under distributed impulse loads. Computational results demonstrated the excellent anti-explosion performance of the proposed ARBW design. Concerning the minimal deformation at the mid-point of the proposed protective structures, the ARBW performed best. As regards the minimal deformation at the connection, both ARBW and HSBW worked well. The stress distribution of the connection illustrated the different energy absorption and transmission modes of the three blast walls.

Topsides of offshore platforms contain different equipments, therefore earthquake excitation may impose large forces on them. In designing these topsides, the interaction of the secondary systems and primary structure is not usually considered, which is not realistic. In order to study this subject a 3D model of a typical platform in the Persian Gulf is constructed and analyzed, using OpenSees software, when subjected to different records. These records are scaled for two earthquake levels. In the first level the structure is in elastic condition but for the second level it behaves inelastically. According to the results, in secondary systems with low periods of vibration, structure and secondary system interactions can be neglected. But when the period of secondary system is increased, it is necessary to consider interactions effects.

Flammable gas dispersion and deflagration above sea resulting from subsea release have the possibility to cause an adverse impact on the operation safety of surface vessels. This paper presents a systematic simulation of gas dispersion and deflagration above sea from a subsea release using CFD-based approach, aiming to study the evolution process of accident scenario and assess its impact on surface vessels. A jack-up drilling platform is used as a case to discuss the impact of gas dispersion and deflagration. The uniqueness of this study is the integration of release, dispersion, and deflagration scenarios. The simulation includes the modelling of wind flow, gas dispersion and subsequent deflagration due to accidental ignition. The wind flow above sea surface is given using wind speed profile equation to generate steady wind field around offshore platform. Simulation of gas dispersion is conducted based on the generated wind field. The development of flammable gas cloud is predicted, and the dangerous area on offshore platform is assessed. Considering the appearance of ignition source, a deflagration simulation based on dispersion results is performed to predict the consequences including overpressure, high temperature, and heat radiation. Eventually, the damage criterion is utilized to evaluate their impact on offshore platform. [ABSTRACT FROM AUTHOR]

The evacuation routes which are selected by crew will affect their evacuation efficiency when an offshore platform under emergency conditions. To quantify the influence of evacuation route selection on crew evacuation efficiency, two scenarios are considered: Scenario1 is that crew independently select the evacuation routes to evacuate to the assembling point, Scenario 2 is that crew evacuate to the assembling point in accordance with the prescribed evacuation routes. The evacuation efficiency of these two evacuation scenarios is analyzed and discussed from the aspect of evacuation time, waiting time index (WTI), optimal performance statistic (OPS), mean non-flow statistic (MNS) and casualty, respectively. It is found that the evacuation time of crew in Scenario 1 reaches 255.09 s, but Scenario 2 is 32.84 s shorter. By analyzing the WTI of each evacuation exit in these two evacuation scenarios, a large number of people in Scenario 1 are congested at the exit 1, which is the main reason for the increase of evacuation time of Scenario 1. Moreover, the comparison of the OPS and MNS of these two evacuation scenarios indicates that crew in Scenario 1 have not made full use of evacuation exit resources and make it impossible for crew to reach the assembling points timely. Furthermore, in Scenario 1, there are ten crew unable to reach the primary assembling point in time. Scenario 2, however, suffers no casualties. [ABSTRACT FROM AUTHOR]

The high-efficient development of heavy oil is difficult for offshore oil field. Based on the mature technology of onshore heavy oil thermal recovery, a new rod pumping technology of “heavy oil steam stimulation along with conventional sucker rod pumping system” is proposed. According to the structure space of aimed offshore platform, we designed one new kind of miniature hydraulic pumping unit with long-stroke, low pumping speed and compact structure. The paper also studies the offshore heavy oil thermal recovery well safety technology, establishes a leakage model of wellhead sealing and a mechanical model of sealed rubber sleeve on downhole nonlinear large deformation. The study shows that a series of equipment for offshore rod pumping oil recovery and the key technology of well safety lay a solid foundation for carrying out rod pumping of offshore heavy oil thermal recovery. [ABSTRACT FROM AUTHOR]

In this paper, we investigate a H ∞ memory controller with input limitation minimization (HMCIM) for offshore jacket platforms stabilization. The main objective of this study is to reduce the control consumption as well as protect the actuator when satisfying the requirement of the system performance. First, we introduce a dynamic model of offshore platform with low order main modes based on mode reduction method in numerical analysis. Then, based on H ∞ control theory and matrix inequality techniques, we develop a novel H ∞ memory controller with input limitation. Furthermore, a non-convex optimization model to minimize input energy consumption is proposed. Since it is difficult to solve this non-convex optimization model by optimization algorithm, we use a relaxation method with matrix operations to transform this non-convex optimization model to be a convex optimization model. Thus, it could be solved by a standard convex optimization solver in MATLAB or CPLEX. Finally, several numerical examples are given to validate the proposed models and methods. [ABSTRACT FROM AUTHOR]

Accurate knowledge of the detailed status (location and lifetime) of each oil/gas platform is crucial for ocean management and for understanding its potential environmental impact. However, this requirement is often compromised due to incomplete data records, especially when platform abandonment is not properly planned, designed, and/or executed. The availability of multi-source optical and SAR images provides the possibility of a systematic assessment, but the ubiquitous false positives and frequent geocoding errors make it technically challenging. Here, we develop a time-series remote sensing approach (TSRS) for detecting offshore platforms and determining their status, where the technical challenges are overcome using two strategies, as follows: ( i ) A stepwise optimization strategy applied to individual images and time-series images to mitigate numerous noises, to select platforms from candidates, and to assess platform status; and ( ii ) A cross geo-correction strategy using platforms derived from high-geometric accuracy images as ground control points to rectify poorly geo-referenced images. We applied the TSRS approach to the northern Gulf of Mexico using about 26,000 moderate-resolution optical/SAR images from eight satellites spanning the period from 1982 to 2017. TSRS detected a total of 9260 (5556) platforms in both Federal and State waters, including 3140 (1803) existing platforms, 5044 (3426) removed platforms, and 1076 (327) status-to-be-determined platforms where the numbers in parentheses represent those from Federal waters. Of these TSRS platforms, 4751 coincide spatially with 5476 (77.68%) of platform records of the Bureau of Safety and Environmental Enforcement (BSEE) platform database; 2846 (387 in Federal waters) are not found in the BSEE platform database but are convincingly supported by data from other sources (including BSEE-pipeline-database, time-series VIIRS nighttime light products, and littoral ground-truth images), meaning that 82.04% of the TSRS-derived platforms can be directly/indirectly confirmed. A site-specific validation in East Bay using multi-temporal ground-truth aerial images indicates that, for this site, the false negative rate (FNR) is ~9.63% and the false positive rate (FPR) is only 4.44%. The detailed beginning/end dates of the TSRS platforms are mostly confirmed by the corresponding Installation/Site-clear dates recorded in the BSEE platform database. Our findings suggest that the TSRS approach is a robust and cost-effective way to assess oil/gas platform status in large regions, and our results here may complement the official database, narrow down locations for future field investigations, and provide critical information for future assessment of the potential impacts of active and decommissioned platforms on the marine environments. [ABSTRACT FROM AUTHOR]

The assessment of the exergy spent for production of oil and gas on offshore platforms is of primordial importance for evaluation of the environmental impact associated with petroleum derived substances. In this work the exergy cost for oil and gas produced on a Floating Production Storage and Offload (FPSO) ship is evaluated along the lifespan of the well taking off-design operation conditions of process plant and cogeneration plant into account. The impact of 3 different cogeneration plants and 2 different process plant operating modes was assessed. Distribution of exergy costs for the oil and gas was obtained using thermoeconomy to reduce the arbitrariness of cost partition criteria. Results reveal that the exergy cost of oil varies from 1.0 kJ/kJ to 3.2 kJ/kJ along the well lifespan depending on process plant operating mode and cogeneration plant configuration. The exergy cost of gas varies from 1.0 kJ/kJ to 2.4 kJ/kJ along the well lifespan depending on cogeneration plant configuration. The average emission of CO 2 for the natural gas ranges from 19.0 gCO2/MJ to 19.8 gCO2/MJ depending on the cogeneration plant configuration while for the oil it ranges from 19.4 gCO2/MJ to 26.8 gCO2/MJ and it also depends on process plant operating mode. [ABSTRACT FROM AUTHOR]

Large offshore production platform designs are characterized by high levels of horsepower for driven equipment. It is common to design around an all-electric approach, where a central electrical power plant is installed and few (if any) turbine or diesel engine drivers are included other than for generators. This approach leads to the use of relatively large transformers and to higher levels of available short-circuit current. Due to the production throughput and the capital investment associated with these facilities, the availability of electric power is a prime economic factor in design. To enhance both maintainability and operability of the electrical plant itself, dual radial secondary selective systems with main-tie-main breaker switchgear configurations are frequently employed. If one of the main supplies is intentionally removed from service, it is usually preferable to first closed-transition transfer the affected loads to the other main supply through the tie breaker. During this closed-transition transfer period, the switchgear may be exposed to an excessive level of available short-circuit current. This paper discusses this closed-transition transfer scheme and addresses safeguards that may be taken to mitigate the excessive short-circuit current risks during the transfer period. [ABSTRACT FROM AUTHOR]

The aim of this research is to develop an algorithm and application that can perform real-time monitoring of the safety operation of offshore platforms and subsea gas pipelines as well as determine the need for ship inspection using data obtained from automatic identification system (AIS). The research also focuses on the integration of shipping database, AIS data, and others to develop a prototype for designing a real-time monitoring system of offshore platforms and pipelines. A simple concept is used in the development of this prototype, which is achieved by using an overlaying map that outlines the coordinates of the offshore platform and subsea gas pipeline with the ship’s coordinates (longitude/latitude) as detected by AIS. Using such information, we can then build an early warning system (EWS) relayed through short message service (SMS), email, or other means when the ship enters the restricted and exclusion zone of platforms and pipelines. The ship inspection system is developed by combining several attributes. Then, decision analysis software is employed to prioritize the vessel’s four attributes, including ship age, ship type, classification, and flag state. Results show that the EWS can increase the safety level of offshore platforms and pipelines, as well as the efficient use of patrol boats in monitoring the safety of the facilities. Meanwhile, ship inspection enables the port to prioritize the ship to be inspected in accordance with the priority ranking inspection score. [ABSTRACT FROM AUTHOR]

In this paper, a numerical investigation of a float-over installation for an offshore platform is presented to verify the feasibility of the actual installation. The hydrodynamic performance of a T-barge is investigated in the frequency domain, and the coupled motions are analyzed in the time domain. We then compare with those of the model test and determine that the response amplitude operator and the time series agree quite well. The barge exhibits favorable hydrodynamic behavior in the considered sea state, and the equipment loads are allowable. The mooring system and sway fender forces are within the permissible range. Based on these results, we can verify that the actual installation of the offshore platform is feasible. We accurately simulated many important factors and effectively reduced the risk associated with the offshore installation, which is of great importance. As such, we demonstrate that the numerical simulation of the float-over installation for offshore platforms has practical engineering significance. [ABSTRACT FROM AUTHOR]

Floatover installation is an effective installation method for topsides of offshore platforms. The floatover operation is very sensitive to the ocean environment conditions, and the motions of the topside are required to be strictly limited within a certain level. The field monitoring is essential to support the installation. This paper presents a comprehensive introduction to the monitoring system developed by Shanghai Jiao Tong University for the jacket platform floatover installations. Four subsystems were designed for the purposes of environment monitoring, motions and position monitoring, deck support unit (DSU) separating monitoring and closed-circuit television (CCTV) monitoring, respectively. Besides, the integrated monitoring system (IMS) for data integration is also introduced. In addition, applications of the monitoring system with respect to a recently implemented floatover installation project in Malaysian waters is presented. The execution plan is introduced in details, and the implementation process for the monitoring system including validation, installation, tests and field operation is presented. Moreover, the field monitoring results are presented and discussed in brief. [ABSTRACT FROM AUTHOR]

A finite element model (FEM) of the offshore platform with biofouling is developed here to predict the effectiveness of the ICCP under seawater. Remotely operated vehicle (ROV) test verified that the offshore platform was fully covered by a coating‐like biofouling to protect the structures from corrosion. FE‐SEM and EDS tests demonstrated that the biofouling deposits on the offshore platform mainly contained magnesium oxides, biofouling deposits, and corrosion products doped with calcium oxides. The polarization relationships of platform steel with biofouling coverage were used as boundary conditions for the numerical simulation. Furthermore, the factors including output current, anode location, seawater conductivity, and biofouling coverage rate, which influenced the protective effectiveness, were comparatively evaluated by FEM. Then, a re‐design two‐anode ICCP system was employed to keep offshore platform in protective condition. A ROV monitored the potential distributions of the legs and demonstrated that numerical simulation results of ICCP had a good agreement with measured data. [ABSTRACT FROM AUTHOR]

A new technology of offshore oil rod pumping production is developed for offshore heavy oil recovery. A new type of miniature hydraulic pumping unit with long-stroke, low pumping speed and compact structure is designed based on the spatial characteristics of offshore platforms. By combining the strengths of sinusoidal velocity curve and trapezoidal velocity curve, a kinematical model of the acceleration, the velocity and displacement of the pumping unit's hanging point is established. The results show that the pumping unit has good kinematic characteristics of smooth motion and small dynamic load. The multi-degree-of-freedom dynamic model of the single-well pumping unit is established. The first and second order natural frequencies of the sucker rod string subsystem and the pumping unit subsystem are studied. The results show that the first and the second order natural frequencies among the pumping rod string, pumping unit-platform subsystem and the dynamic excitation have differences over 5 times from each other, indicating that resonance phenomenon will not appear during the operation and the dynamic requirements for field use are met in the system. [ABSTRACT FROM AUTHOR]

Grouted connections are frequently used as structural detail of offshore wind turbines and platforms for the load transferring connection between piles and support structure. At latticed substructures this connection is commonly located at mudline. However, a potential influence of the surrounding water on the connection’s fatigue behaviour was neglected in earlier tests and consequential design methods. Herein described experimental investigations at small and large-scale fatigue tests in submerged conditions showed a significant reduction of endurable load cycles. In addition, the water impact caused varied damage mechanism in the connection. [ABSTRACT FROM AUTHOR]

Copyright of China Petroleum Machinery is the property of China Petroleum Machinery Editorial Department 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.)

Offshore structures are critical infrastructure in the field of ocean engineering, which may under the threat of earthquake shaking, especially when they are located in the high-risk seismic zones. This paper proposes using an innovative inerter-based damping isolation system (IDIS) for the seismic protection of offshore platforms. The concept of IDIS is firstly proposed by integrating the conventional bearings with inerter-based dampers (IDs). An analytical model of the system is established, and the corresponding equilibrium equations of motion are derived. Without loss of generality, the deck acceleration, displacement on the jacket cap, and isolating layer deformation are chosen as the performance objectives, and parametric analyses are performed to investigate the influences of the key parameters of IDIS on each performance objective. A performance-based multi-objective optimization framework is then developed for determining the optimal parameters of IDIS. The control effectiveness of IDIS is demonstrated in the frequency domain and compared to that of the traditional damping isolation system (DIS). Finally, case studies are performed to further investigate the performance of IDIS subjected to natural seabed ground motions. The results show that properly optimized IDIS is more effective than the conventional DIS in terms of not only the structural responses but also the deformation of the isolating layer. The proposed IDIS can be an attractive and effective alternative to the conventional DIS in the vibration control of offshore platforms. • Inerter-based damping isolation system (IDIS) is proposed for offshore platforms. • Performance-oriented multiple-objective optimization is formulated for IDIS. • Control effectiveness of IDIS is investigated in both frequency and time domains. [ABSTRACT FROM AUTHOR]

Natural gas jet fire induced by igniting blowouts has the potential to cause critical structure damage and great casualties of offshore platforms. Real-time natural gas jet fire plume prediction is essential to support the emergency planning to mitigate subsequent damage consequence and ocean pollution. Deep learning based on a large amount of Computational fluid dynamics (CFD) simulations has recently been applied to real-time fire modeling. However, existing approaches based on point-estimation theory are 'over-confident' when prediction deficiency exists, which reduce robustness and accuracy for emergency planning support. This study proposes probabilistic deep learning approach for real-time natural gas jet fire consequence modeling by integrating variational Bayesian inference with deep learning. Numerical model of natural gas jet fire from offshore platform is built and the natural gas jet fire scenarios are simulated to construct the benchmark dataset. Sensitivity analysis of pre-defined parameters such as MC (Monte Carlo) sampling number m and dropout probability p is conducted to determine the trade-off between model's accuracy and efficiency. The results demonstrated our model exhibits competitive accuracy with R 2 = 0.965 and real-time capacity with an inference time of 12 ms. In addition, the predicted spatial uncertainty corresponding to spatial jet fire flame plume provides more comprehensive and reliable support for the following mitigation decision-makings compared to the state-of-the-art point-estimation based deep learning model. This study provides a robust alternative for constructing a digital twin of fire and explosion associated emergency management on offshore platforms. • Advanced deep probabilistic learning-based real-time natural gas jet fire prediction model of offshore platform is proposed. • Proposed model integrates variational Bayesian inference with deep learning backbone. • Optimal variational hyperparameters of proposed model is determined. • Model provides more robust fire consequence estimation of offshore platform compared to state-of-the-art models. [ABSTRACT FROM AUTHOR]

The study of evacuation from offshore platforms under restricted visibility conditions has received little attention in previous studies. Therefore, evacuation performance on offshore platforms considering different visibility conditions is investigated in the study using agent-based techniques. First, the evacuation speed model is modified and validated based on the experimental data. Then, cases are designed considering different visibility conditions, and the simulation results are analyzed and discussed in terms of evacuation time, evacuation flow rate and queuing time. The results show that the visibility distance has a significant impact on the evacuation process. Based on the difference in evacuation flow rate, the evacuation process is split into two phases. Statistical methods are used to determine the relationship between the flow rate and visibility distance for both phases. Phenomena like "long tail effect" and queuing are observed that can affect the evacuation efficiency. The reasons behind the phenomena are then explored. Finally, the effect of smoke visibility on the evacuation process is studied. It is found that the smoke visibility in a fire accident can negatively affect the evacuation efficiency, with the workers on the lower and working decks being most adversely affected. As a result, the flow rates in both phases are reduced. Additionally, investigations have been conducted on how the pre-evacuation time affects the evacuation efficiency in Case C. It demonstrates that the longer the pre-evacuation time, the lower the flow rate becomes, indicating that the greater the impact of smoke visibility on evacuation efficiency. This study may be useful for predicting the evacuation process on offshore platforms under restricted visibility conditions, and it may also provide suggestions for the formation of evacuation strategies. • A modified evacuation speed model taking into account the effect of visibility distance was established. • The evacuation performance on an offshore platform considering different restricted visibility conditions was investigated by using the improved Fire Dynamics Simulator and Evacuation (FDS+EVAC) software. • The phenomena like "long tail effect" and "queuing" were observed, and their effects on the overall evacuation efficiency were investigated quantitatively. [ABSTRACT FROM AUTHOR]

Natural gas explosion of offshore platform is prone to cause accidental disaster such as platform collapse and casualties etc. Real-time natural gas explosion consequence reconstruction is essential to support a quick accidental emergency response planning to prevent the accidental escalation to disaster. The widely-used CFD is computationally intensive and thereby has a significant delay. Machine/deep learning-based models offer a potential real-time alternative, which however are not able to quantify the uncertainty of spatial overpressure prediction. This study aims to propose a hybrid deep learning probability model to real-time predict spatial explosion overpressure of offshore platform by using sparsely-observed overpressures. In this hybrid model, Variational Bayesian inference is incorporated into deep learning backbone. Both natural gas explosion experimental and numerical modeling of offshore platform are conducted to construct the benchmark dataset. By using this benchmark dataset, sensitivity analysis of Monte Carlo sampling number N , drop probability p on model's performance is also conducted. The results demonstrated our model exhibits high accuracy with R 2 = 0.955 and real-time capability with inference time of 2.9s. Compared to the state-of-the-art model, the additional uncertainty estimation improves the accuracy and robustness of spatial overpressure prediction, which contributes to the reliable explosion accidental emergency decision-making. Overall, this study provides a reliable alternative for constructing digital twin emergency management system to effectively manage natural gas explosion risk of offshore platforms. • Deep learning probability model for real-time natural gas explosion prediction of offshore platforms. • Model correlates spatial explosion overpressure with sparsely-observed overpressures. • Uncertainty information ensures reliable guidance for emergency decision-makings. [ABSTRACT FROM AUTHOR]

Estimation of wave run-up has been of increasing concern for offshore wind structures and a critical aspect for designers. The highly nonlinear phenomenon makes the study difficult. That is the reason for the very few design rules and experimental data available to estimate it. Actual wave run-up is greater than commonly predicted. The goal of this research is to benchmark the theoretical formulations with the results of the physical model tests performed by Deltares in the field of crest elevation, run-up, forces and pressures. The laboratory reproduced in a wave tank (75 m length; 8.7 m width; 1 m depth; and a 1:60 scale, with Froude similarity) an offshore power converter platform located at intermediate water depths (25⁻43.80 m) in the Southern North Sea, designed by the Norwegian company Aibel. The purpose of this research is to offer a preliminary design guide for wave run⁻up using theoretical expressions both for cylinders and gravity based structures (GBS), leaning on the cited laboratory tests to validate the results obtained by such theoretical models.