Search

The increasing energy demand has led to more explorations in the oil and gas industry. To achieve this, marine risers and pipelines are used to convey fluid and other resources to meet the increasing demand. In recent years, hybrid flexible composite risers have become more adaptable. Flexible risers have already proven to be a popular riser solution for various floating production systems in shallow to deepwater in many parts of the world due to their good dynamic behaviour and dependability. The hybrid flexible composite riser is made up of numerous layers of plastics, flexible pipes, composites, and steel. Some innovative monitoring methods, such as Fiber Optics Bragg Gratings (FBG), are based on a clamped composite structure with embedded optical fibre. This study presents characteristics of the monitoring techniques of composite flexible riser technology. The advantages of the monitoring techniques include aiding composite riser measurements, recording data from riser deformation, improving integrity assurance, and dependability of design from stable readings. It also proposes some design approaches as guidelines that are advised, with some policy implications.

In this paper, the propagation characteristics of vibration waves in periodic pipelines were studied based on the band theory of phononic crystals, and we analyzed the influence of the geometrical structure parameters on the band gap characteristics of pipelines. The results show that, by increasing the number of layers of local resonant structure, both the initial frequency and the cutoff frequency of the band gap moved towards the lower frequency, while the width of the system band gap increased by 35 Hz, and the damping effect increased by 18.3 dB. By changing the thickness of the wall of the pipeline system, the width of the system band gap increased by 20 Hz, and the damping effect increased by 9.1 dB. The maximum vibration isolation of the offshore platform truss based on the periodic structure can be up to 7.93 dB. Therefore, it is feasible to apply the local resonant periodic structure to the vibration control of a practical offshore platform.

This paper deals with the problems of networked modelling and memory-event-triggering H ∞ reliable control for steel jacket-type platforms in network environments. First, a networked model of the jacket platform against earthquakes and probabilistic actuator faults is established. Based on this model, a memory-based event-triggering communication scheme is introduced to account for the constrained communication resources. A distinct feature of the proposed triggering scheme is that it has great potential to identify and trigger the significantly changed data than the existing ones without 'memory'. Then, by formulating the network-based closed-loop platform system as a stochastic delay system, some sufficient conditions are derived for co-designing the desired controller and the triggering scheme. Finally, comparative simulation results are provided to demonstrate the effectiveness and merits of the proposed triggering and control co-design method. It is shown that compared with some existing event-triggering control methods, the proposed memory-event-triggering H ∞ reliable controller is effective to mitigate vibrations of the jacket platform and is potentially advantageous to save more network bandwidth and control cost. [ABSTRACT FROM AUTHOR]

The fault tree analysis (FTA) is one of the important probabilistic risk assessment tools that is extensively used in different industrial applications. However, the classical FTA has been widely criticized due to its ambiguity and vagueness in finding the probability of basic events (BEs), and accordingly, in computing the probability of top events (TEs). In this paper, we propose a new approach considering the integration of fuzzy set theory and evidence theory for handling both types of uncertainties, i.e., epistemic and aleatory. In addition, to estimate the probability of TEs alternatively, the normal distribution is applied. By performing a numerical example of risk assessment in a collapse case study for a common offshore facility platform, the effectiveness of the approach is demonstrated. Finally, in this study, the sensitivity analysis is also performed to represent the vulnerability of the causes and the interaction of different inputs, meaning that the proposed model is highly reliable and effective for real applications. [ABSTRACT FROM AUTHOR]

Fixed offshore platforms in the Gulf of Mexico (GoM) are traditionally designed following the working stress design (WSD) format, that is, the factor of safety approach. In 1993, the first reliability-based design standard for offshore platforms using the Load and Resistance Factor Design (LRFD) format was published by the American Petroleum Institute (API) called Recommended Practice for Planning, Designing, and Constructing Fixed Offshore Platforms—Load and Resistance Factor Design, which is commonly abbreviated as API RP 2A-LRFD 1st edition. API RP 2A-LRFD 1st edition has had a significant influence in developing the LRFD format of the ISO for fixed offshore structures (i.e., ISO 19902), but it was not commonly used in the United States, and it was withdrawn in 2012 due to a lack of maintenance. The API RP 2A-LRFD format was reintroduced in 2014 as a draft 2nd edition. This study was carried out in the context of the plan to prepare the API RP 2A-LRFD 2nd edition under the effort to align and merge the API and ISO standards as a single global standard. The objectives of this study are to assess the fixed offshore platform component reliability with the accumulated experience in the last several decades, and to evaluate the suitability of the load and resistance factors in API RP 2A-LRFD 1st edition for the 2nd edition of API LRFD given the updated metocean characteristics after Hurricane Katrina in the GoM. The key findings of this study are that the LRFD format with the load and resistance factors from API RP2A-LRFD 1st edition gives slightly higher reliability levels for component checks than the WSD format, but lower reliability level with the updated new metocean criteria comparing to the criteria in the 1980s. A list of recommendations on the load and resistance factors was provided to facilitate the preparation for the API RP2A-LRFD 2nd edition. [ABSTRACT FROM AUTHOR]

Coupled dynamic analyses of a deep-water Semi-submersible platform, in the South China Sea region, is carried out under postulated damage of the restraining system for both 10 and 100-years return period events. Under the combined action of wind, wave, and current loads, motion responses of Semi-submersible at 1500 and 2000 m water depths are analyzed in time-domain. Dynamic tension variations in the mooring lines are investigated for a fatigue failure using the S–N curve approach. Inclusion of a submerged buoy in the mooring system resulted in a marginal increase of the response due to a reduction in the restoration force of the mooring lines; submerged buoy also resulted in additional damping. The results of numerical studies showed an increase in tension in the mooring lines, which are adjacent to the damaged ones, causing reduced fatigue life. With the inclusion of submerged buoy in the mooring system, there is a considerable decrease in tension variation in mooring lines, increasing fatigue life. Failure of a mooring line causes an increase in tension of the adjacent mooring line, but not valid under all circumstances. It is seen from the studies that despite the postulated failure induced in a mooring, the adjoining line remains unaffected due to a steady coupling motion of the platform. [ABSTRACT FROM AUTHOR]

The identification of variations in the dynamic behavior of structures is an important subject in structural integrity assessment. Improvement and servicing of offshore platforms in the marine environment with constant changing, requires understanding the real behavior of these structures to prevent possible failure. In this work, empirical and numerical models of jacket structure are investigated. A test on experimental modal analysis is accomplished to acquire the response of structure and a mathematical model of the jacket structure is also performed. Then, based on the control theory using developed reduction system, the matrices of the platform model is calibrated and updated. The current methodology can be applied to prepare the finite element model to be more adaptable to the empirical model. Calibrated results with the proposed approach in this paper are very close to those of the actual model and also this technique leads to a reduction in the amount of calculations and expenses. The research clearly confirms that the dynamic behavior of fixed marine structures should be designed and assessed considering the calibrated analytical models for the safety of these structures. [ABSTRACT FROM AUTHOR]

There are currently thousands of offshore platforms in place for oil and gas extraction worldwide, and decommissioning efforts over the next three decades are estimated to cost more than US$200 billion. As platforms reach the end of their useful lifetime, operators and regulatory agencies will assess the environmental impact of potential decommissioning strategies. Among the many factors that will be weighed in preparation for these major economic and engineering challenges is the fate of the fish and invertebrate communities that inhabit the structures underwater. Offshore platforms act as inadvertent artificial reefs, and some are recognized among the most productive fish habitats in the global oceans. We present a model for forecasting changes to fish communities surrounding offshore installations following a series of decommissioning alternatives. Using 24 platforms off southern California, we estimate fish biomass and somatic production under three possible decommissioning scenarios: leave in place, partial removal at 26‐m depth, and complete removal of the platform and underlying shell mound. We used fish density and size data from scuba and submersible surveys of the platforms from 1995–2013 to estimate biomass and annual somatic production. Bottom trawl surveys were used to characterize future fish assemblages at platform sites under the complete‐removal decommissioning scenario. Based on a conservatively modeled extrapolation of the survey data, we found that complete removal of a platform resulted in 95% or more reduction in the average fish biomass and annual somatic production at the site, while partial removal resulted in far smaller losses, averaging 10% or less. In the event that all surveyed platforms are completely removed, we estimated a total loss of more than 28,000 kg of fish biomass in the Southern California Bight. Platform habitats, which attract reef‐dwelling fish species, had minimal overlap in community composition with the surrounding soft‐bottom habitat. To best serve the wide range of stakeholder interests, the site‐specific biomass, productivity and species composition information provided in this study should be incorporated into strategic decommissioning planning. This approach could be used as a model for informing "rigs to reefs" discussions occurring worldwide. [ABSTRACT FROM AUTHOR]

The development of heavy oil with high efficiency is a worldwide difficulty for offshore oil field. The technology of rod pumping provides a possible effective way for offshore heavy oil thermal recovery, but the safety of working platform is the prerequisite for the implementation of this new technology. In this paper, the mechanical model of LD27-2 WHPB platform is established, and the safety performance of the platform under hydraulic pumping unit (HPU) load is evaluated. The distribution of the combined HPU load accords with the classical probability model. When the HPUs are all synchronous, the combined load reaches its maximum. The finite element-based platform safety analysis under the extreme condition is carried out. Under the combined action of wave current, wind load and the extreme HPU load, the maximum stress of the jacket is 83.2 MPa, and the safety coefficient is 4.33, indicating the overall strength of LD27-2 WHPB platform meets the safety requirement. [ABSTRACT FROM AUTHOR]

Recent research on wind-farm control methods has focused until now on maximising the efficiency and durability of farm operations, as verified for a normalised electrical layout. However, with the increase of turbine size and capacity, it is necessary to develop modifications of the farm management plan that can support the increasing demands of the wind-turbine industry. Here the authors propose a modification that focuses on a proportional reactive power-dispatch method that is applied to radial offshore farm networks. They improve a previously developed method of proportionally distributing reactive power commands by considering the actual configuration of an offshore platform. To confirm the applicability of this method in transient state, they examine case studies using a time-varying signal for a reactive power reference under fluctuating wind. Electromagnetic transients using DC software tools are used to estimate the electrical loss and verify the efficiency of this strategy. [ABSTRACT FROM AUTHOR]

The requirements for the fire resistance of steel structures of oil and gas facilities for transportation and production of hydrocarbons are considered (structures of tankers and offshore platforms). It is found that the requirements for the values of fire resistance of structures under hydrocarbon rather than standard fire conditions are given only for offshore stationary platforms. Experimental studies on the loss of integrity (E) and thermal insulating capacity (I) of steel bulkheads and deck with mineral wool under standard and hydrocarbon fire regimes are presented. Simulation of structure heating was performed, which showed a good correlation with the experimental results (convective heat transfer coefficients for bulkheads of class H: 50 W/m2·K; for bulkheads of class A: 25 W/m2·K). The consumption of mineral slabs and endothermic mat for the H-0 bulkhead is predicted. It is calculated that under a standard fire regime, mineral wool with a density of 80–100 kg/m2 and a thickness of 40 to 85 mm should be used; under a hydrocarbon fire regime, mineral wool with a density above 100 kg/m2 and a thickness of 60–150 mm is required. It is shown that to protect the structures of decks and bulkheads in a hydrocarbon fire regime, it is necessary to use 30–40% more thermal insulation and apply the highest density of fire-retardant material compared to the standard fire regime. Parameters of thermal conductivity and heat capacity of the applied flame retardant in the temperature range from 0 to 1000 °C were clarified.

Complexity and costly nature of operations involving in the decommissioning process require huge investments to be done during the lifetime of the field for its decommissioning phase of the total project. This work offers a knowledge-based decommissioning alternative strategy selection system for fixed offshore jacket platforms in the Persian Gulf. In this method, the alternative option of installing offshore wind turbines (OWT) as the most probable economic feasible alternative to decommissioning on an abandoned platform jacket structure in the Persian Gulf is proposed. In this regard, costs and benefits study between two strategies are considered; one total decommissioning and the other installing an OWT on the jacket structure of a local platform in the region. It is found that the second strategy is beneficial and saves near 9 million US dollars for company. Furthermore, the company earns the technology and experiences with OWT installation and operations and would be a technical leader in the region for coming years as well as improve the total rate of greenhouse gas emission production in the region.

Copyright of Journal of China University of Petroleum is the property of China University of Petroleum 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.)

Structural health monitoring has become increasingly important in the effective evaluation of structural health conditions and the maintenance service of structures. The validity and convenience of obtaining sensor data are critical for data mining, feature extraction, and condition assessment. A fast wireless low-frequency vibration inspection system (FWLVIS) based on wireless sensor networks for offshore platform structural vibration inspection is presented in this paper. The designed system consists of intelligent acquisition equipment and eight wireless nodes with low-frequency acceleration sensors, while the entire system has 64 collection channels. The wireless nodes integrated with a vibration sensing unit, an embedded low-power micro-processing unit, a wireless transceiver unit, and a large-capacity power unit perform functions, which could perform data collection, initial analysis, data storage, and wireless transmission. The intelligent acquisition equipment integrated with a high-performance computation unit, a wireless transceiver unit, a mobile power source, and the embedded data analysis software could completely control the multi-wireless nodes, receive and analyze the data, and implement the parameter identification. Experiments are performed on a single pendulum, and then on an offshore platform model is constructed to verify the FWLVIS. The experimental results show that the system has the following characteristics: fast arrangement, high sampling rate, high resolution, and capacity for low-frequency inspection. Thus, the system has good application prospects and practical value in the field of structural health monitoring and non-destructive inspection. [ABSTRACT FROM AUTHOR]

Natural gas leakage on offshore platforms has a great impact on safety production, and effective and reasonable leakage detection methods can prevent the harm caused by natural gas leakage. This article proposes a method based on ant colony optimization (ACO) for multirobots to collaboratively search for leaking natural gas sources on offshore platforms. First, analyze the structure and environment of the offshore platform, use Fluent software to simulate the diffusion process of natural gas leaked from the platform, and establish a diffusion model of natural gas leaked from various aspects, such as the layout of different platforms, the number of leaked gas sources, and the concentration of leaked gas sources. In terms of multirobot cooperative control, we analyzed and improved the ant colony algorithm and proposed a multirobot cooperative search strategy for gas search, gas tracking, and gas source positioning. The multirobot search process was simulated using MATLAB software, and the robot on the detection effect of multirobots was analyzed in many aspects, such as quantity, location of leak source, and a number of leak sources, which verified the feasibility and effectiveness of the multirobot control strategy based on optimized ACO. Finally, we analyze and compare the two control algorithms based on ACO and cuckoo search algorithm (CSA). The results show that the ACO-based multirobot air source positioning effect is significantly better than CSA. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Petrochemical Universities / Shiyou Huagong Gaodeng Xuexiao Xuebao is the property of Journal Editorial Department Of Liaoning Shihua University 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 paper investigates the possibility of utilizing response from natural ice loading for modal parameter identification of real offshore platforms. The test platform is the JZ20-2MUQ jacket platform located in the Liaodong Bay, China. A field experiment is carried out in winter season, as the platform is excited by floating ices. The feasibility is demonstrated by the acceleration response of two different segments. By the SSI-data method, the modal frequencies and damping ratios of four structural modes can be successfully identified from both segments. The estimated information from both segments is almost identical, which demonstrates that the modal identification is trustworthy. Furthermore, by taking the Jacket platform as a benchmark, the numerical performance of five popular time-domain EMA methods is systematically compared from different viewpoints. The comparisons are categorized as: (1) stochastic methods versus deterministic methods; (2) high-order methods versus low-order methods; (3) data-driven versus covariance-driven stochastic subspace identification methods. [ABSTRACT FROM AUTHOR]

Data obtained during and after major hurricanes in the Gulf of Mexico (GoM) in the past three decades provide valuable information about the design model uncertainties for fixed steel offshore platforms because multiple offshore platforms were loaded close to and/or beyond the predicted capacity and, in particular, because multiple damages/failures were observed in the jacket superstructures, and a three-pile jacket system was well documented and extensively studied in the postfailure stage. The objective of this paper is to extract information on the current fixed offshore platform design practice by comparing the predicted versus observed performance of 18 offshore platforms in five major GoM hurricanes using Bayes' theorem. The Bayesian calibration indicates that the American Petroleum Institute design recipe, on average, (1) is close to being unbiased for assessing the safety margin for the jacket superstructure performance, (2) tends to be unbiased for the pile lateral capacity using the upper bound lateral bearing factor in p-y curves with the mean yield strength of pile steel, (3) is slightly conservative by 5% for the pile axial capacity in clay, and (4) is conservative by close to 50% for the pile axial capacity in sand. It is concluded that a jacket system with four or more legs/piles is less likely to fail in the foundation system than in the superstructure. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Petrochemical Universities / Shiyou Huagong Gaodeng Xuexiao Xuebao is the property of Journal Editorial Department Of Liaoning Shihua University 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.)

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.)

In-place analysis for offshore platforms is essentially required to make proper design for new structures and true assessment for existing structures, in addition to the structural integrity of platforms components under the maximum and minimum operating loads when subjected to the environmental conditions. In-place analysis have been executed to check that the structural member with all appurtenance's robustness have the capability to support the applied loads in either storm or operating conditions. A nonlinear finite element analysis is adopted for the platform structure above the seabed and pile-soil interaction to estimate the in-place behavior of a typical fixed offshore platform. The SACS software is utilized to calculate the dynamic characteristics of the platform model and the response of platform joints then the stresses at selected members, as well as their nodal displacements. The directions of environmental loads and water depth variations have significant effects in the results of the in-place analysis behavior. The most of bending moment responses of the piles are in the first fourth of pile penetration depth from pile head level. The axial deformations of piles in all load combinations cases of all piles are inversely proportional with penetration depth. The largest values of axial soil reaction are shown at the pile tips levels (the maximum penetration level). The most of lateral soil reactions resultant are in the first third of pile penetration depth from pile head level and approximately vanished after that penetration. The influence of the soil-structure interaction on the response of the jacket foundation predicts that the flexible foundation model is necessary to estimate the force responses demands of the offshore platform with a piled jacket-support structure well. [ABSTRACT FROM AUTHOR]

Vapor cloud explosion (VCE) accidents have the potential to cause loss of life in offshore platforms. In order to quantify risk, quantitative risk assessment has served as a robust methodology. However, previous research focuses on macroscale assessment of risk which does not take into consideration the local specific details such as piping and equipment congestions. The overpressure developed by VCE is greatly influenced by local specific details. In addition, VCE occurs due to the ignition of vapor cloud that is influenced by parameters such as wind speeds and directions. This study investigates the effect of different wind conditions on VCE and resulting human injury and fatality risk by employing a grid‐based approach in an offshore platform. Flame Acceleration Simulator software is utilized to model dispersion of vapor cloud and resulting VCE. The methodology is an integrated tool that enables a grid‐by‐grid mapping risk, thereby providing a complete and precise picture of risk in all the locations. It was found that risk values were increased to maximum of 91% when wind speed was increased from 0 to 7 m/s. Among four wind directions, West to East wind direction recorded maximum risk values and South to North wind direction recorded minimum risk values. [ABSTRACT FROM AUTHOR]

In order to complete the loading operation in a short time, the genetic algorithm was improved, and the improved mechanisms such as the total crossover of the population and the distributed dynamic penalty function method were proposed. The distribution of ballast water in barge stowage was optimized. The calculation of the ship's floating state, stability, the check of the program strength, and the improvement of the genetic algorithm were discussed. By simplifying the model, all ballast water tanks were involved in the stowage, so as to better meet the limitation of tide level, tank capacity and strength. A more adaptable load optimization solution was obtained. The results show that the improved genetic algorithm has shorter time and higher efficiency than the basic loading scheme. The improved genetic algorithm was used to optimize the barge loading plan, which met the engineering requirements and shorten the working time of the barge. Therefore, the research on the improved genetic algorithm can effectively improve the quality and reliability of the project, which is beneficial to improve the scientific, safety and reliability of the barge loading operation. This program has important implications for marine engineering. [ABSTRACT FROM AUTHOR]

Offshore jacket platforms are widely used for oil and gas extraction as well as transportation in shallow to moderate water depth. Tubular cross‐sectional elements are used to construct offshore platforms. Tubular cross sections impart higher resistance against hydrodynamic forces and have high torsional rigidity. During operation, the members can be partially or fully damaged due to lateral impacts. The lateral impacts can be due to ship collisions or through the impact of falling objects. The impact forces can weaken some members that influence the overall performance of the platform. This demonstrates an urgent need to develop a framework that can accurately forecast dent depth as well as dent angle of the affected members. This study investigates the use of an adaptive metaheuristics algorithm to provide automatic detection of denting damage in an offshore structure. The damage information includes dent depth and the dent angle. A model is developed in combination with the percentage of the dent depth of the damaged member and is used to assess the performance of the method. It demonstrates that small changes in stiffness of individual damaged bracing members are detectable from measurements of global structural motion. [ABSTRACT FROM AUTHOR]

Hydro-dynamic induced vibration is a major risk for offshore platform, which may cause fatigue damdage. The present work experimentally studies a smart isolation system for vibration mitigation of offshore platform utilizing magnetorheological elastomer (MRE). The principle of the proposed MRE-based smart isolation system is presented, in which a real-time decoupling between superstructure (deck) and the jacket structure is achieved by controlling MRE's horizontal stiffness. For a case study, a scaled simplified fixed offshore platform model is built. The prototype of MRE-based isolation system is manufactured and its field-induced dynamic performances are tested. A fuzzy logic controller is proposed for achieving real-time decoupling control. A wave tank testing for the offshore platform with MRE-based isolation system is conducted, in which wave loadings in different dynamic characteristics are considered (e.g., regular and random waves). The results show that the deck acceleration and its displacement, and isolation drift are greatly decreased by the controlled MRE isolation system. It is proven that the smart MRE-based isolation system is able to provide effectiveness vibration suppression for offshore platform structure over a wide range of wave loadings. • Innovation: It is the first experimental investigation on the vibration mitigation of fixed platform by MRE-based variable stiffness isolation system. • Highlight 1: An MRE-based isolation system for reducing wave-induced dynamic responses of fixed platform is numerically studied. • Highlight 2: The testing model of a platform with MRE isolator is developed, and the controllable stiffness of MRE isolator is tested. • Highlight 3: A fuzzy logic controller is proposed to control the performance of MRE isolation system. [ABSTRACT FROM AUTHOR]

Ice loading is the main controlling design load for offshore platforms in Bohai Bay. The ice-induced vibration of offshore platform can be monitored every winter. Both the freezing and drifting sea ice can damage an offshore platform causing structural damage, discomfort for workers, gas leakage and other problems. Two platform designs were studied aiming to reduce ice-induced vibration. One design is the offshore platform with concrete filled double-skin legs (JOP-CFDSL). The other design is the self-centering offshore platform with concrete filled double-skin legs (SRJOP-CFDSL). Both platforms were tested in laboratory experiments, and the data were used to prepare numerical simulations. The results showed that the ice-induced vibration of the two novel jacket platforms are all reduced under push loads, and the SRJOP-CFDSL have better control effect. The replacement of jacket offshore platform's steel circle hollow section legs with concrete filled double-skin legs can effectively improve the structural stiffness. And prestressed tendons were found to improve the platform's performance even further, helping it to reset after lateral impact. It should be noted that the prestressed tendon as an important bearing member, must do some anti-icing protection. Thus, the influence of ice force on the prestressed tendon isn't considered in this paper. • CFDST legs can effectively improve platform's stiffness. • JOP-CFDSL and SRJOP-CFDSL have good ability to resist ice-induced vibration. • SRJOP-CFDSL has great self-centering performance. • SHS improve the corrosion resistance of JOP-CFDSL and SRJOP-CFDSL. [ABSTRACT FROM AUTHOR]

The offshore plant, due to its characteristics, is subject to many restrictions on the material and design of the pipes. Because the design of the firefighting piping depends on the pre-set fire protection design, it is possible to reduce the cost of the piping design by optimizing the arrangement of the firefighting equipment. Existing studies have low accuracy in obtaining service areas under these conditions. In addition, the arrangement optimization problem is generally modeled as a set cover problem (SCP). However, except for the traditional greedy approximation, this problem is not well researched for general solutions. In this paper, first, a modified iterative-deepening search (MIDS), which accurately obtains a service area according to the travel distance in the grid space, is proposed before optimization. Additionally, this paper seeks to define a set cover problem by combining the subsets obtained by MIDS. Second, by using the traditional greedy algorithm, we obtained the initial arrangement of the firefighting equipment. Then, we proposed a method to obtain an approximate optimization solution using a modified greedy method including rearrangement. The validity of the proposed coverage area acquisition and arrangement optimization method is verified by comparing the performance with other algorithms. Finally, this study was applied to the drawings of an actual offshore platform.

Abstract 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.

[Objectives] As one of the key marine equipment technologies,drag chains can provide protection for pipelines on offshore platforms. In order to study the topological relationship and structural strength of drag chains,we take one large drag chain as the research object.[Methods] First,according to the articulated relationship between the inner chain and outer chain,as well as the geometric dimension relationship between the articulated hole and circular arc groove of the inner chain plate,the topological relationships of drag chain are analyzed. The factors,rotation angle and pitch affecting the gyration radius of the drag chain are then acquired. Next,we adopt ANSYS Workbench to analyze the structural strength of the drag chain and obtain its structural response in an unloaded state. On this basis,we retain the original boundary conditions and increase the material density to simulate the stress state of a loaded drag chain,and the ultimate bearing capacity of the drag chain is acquired.[Results] The results show that the articulated shaft at the turning of a drag chain bears the greatest stress.[Conclusions] The findings of this paper show that drag chains are reliable in their use on offshore platforms.

• Absorption of CO 2 from a CO 2 /N 2 mixture with propylene carbonate as the absorbent. • Absorption is carried out in a rotating packed bed. • The experimental conditions have reached the pilot scale. • the gas-side volumetric mass transfer coefficient has been studied. • This method has broad prospects. Absorption of CO 2 from a CO 2 /N 2 mixture with propylene carbonate (PC) as the absorbent using a rotating packed bed (RPB) in pilot scale was systematically investigated in this paper. RPB is characterized by simple operation and high efficiency with small volume, which may be an alternative method for CO 2 removal offshore. The effects of operating parameters on the removal efficiency of CO 2 and the K y a values such as temperature, pressure, inlet liquid flow rate and the rotational speed of RPB were studied. Experimental results indicated that the efficiency of this absorption process could be regulated by appropriate operating conditions of the RPB. [ABSTRACT FROM AUTHOR]

Vibration-based damage identification methods are committed to detecting structural damage by examining changes in the vibration characteristics of structures. However, these characteristics are not only affected by the structural damage but also subject to the change of environmental condition. A new damage localisation method, termed as residual strain energy (RSE) method, which is capable of locating damage on 3D structures under environmental variations, is presented. This RSE method employs the residual mode shapes to construct the damage localisation indicator, in which the principal component analysis algorithm is introduced to eliminate the influence of environmental variations. Numerical simulations were conducted on a 3D offshore platform structure considering temperature variations. Results indicate that the RSE method can effectively eliminate environmental influences and identify structural damage sites correctly. [ABSTRACT FROM AUTHOR]

A fault-tolerant control method based on extended fault diagnostics is proposed for the actuator failure of offshore platforms under the influence of ocean waves. Firstly, a self-repairing fault-tolerant control law is designed for actuator failure. Then an optimal anti-interference self-repairing fault-tolerant controller is designed according to Riccati and Sylvester matrix equations to ensure that the offshore platform system is optimal under fault and wave interference. In order to solve the physical unrealizable problem that the system state and faults in fault-tolerant control cannot be directly measured, an extended fault diagnostic device is designed. Finally, numerical simulation results verify the feasibility and effectiveness of this scheme. [ABSTRACT FROM AUTHOR]