Search

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]

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]

Diverse forms of offshore oil and gas structures are utilized for a wide range of purposes and in varying water depths. They are designed for unique environments and water depths around the world. The applications of these offshore structures require different activities for proper equipment selection, design of platform types, and drilling/production methods. This paper will provide a general overview of these operations as well as the platform classifications. In this paper, a comprehensive review is conducted on different offshore petroleum structures. This study examines the fundamentals of all types of offshore structures (fixed and floating), as well as the applications of these concepts for oil exploration and production. The study also presents various design parameters for state-of-the-art offshore platforms and achievements made in the industry. Finally, suitable types of offshore platforms for various water depths are offered for long-term operations. An extension of this study (Part II) covers sustainable design approaches and project management on these structures; this review helps designers in understanding existing offshore structures, and their uniqueness. Hence, the review also serves as a reference data source for designing new offshore platforms and related structures. [ABSTRACT FROM AUTHOR]

Offshore structures exist in a variety of forms, and they are used for a variety of functions in varied sea depths. These structures are tailored for certain environments and sea depths. Different actions for suitable equipment selection, platform type design, and drilling/production processes are required for the applications of these offshore structures, as given in Part I. This paper is the second part, which outlines various processes, loads, design approaches and project management of offshore platforms. To achieve these, proper planning must be conducted for lifting, transportation, installation, design, fabrication, and commissioning of these offshore platforms. Some historical developments of some offshore structures are presented, and some project planning routines are undertaken in this research. The ultimate goal is to provide a general overview of the many processes of offshore platform design, construction, loadout, transportation, and installation. Some discussions on the design parameters such as water depth and environmental conditions were presented. It also lists various software programs used in engineering designs covering software programs for structural analysis, 3D rendering, computer-aided design (CAD), hydrodynamic design, oceanic flow analysis, offshore structures analysis, mathematical modelling, coding/algorithm development software, and programming software to aid analytical calculations. The review also includes information on cutting-edge offshore platforms and industry advancements. Ultimately, for long-term operations, various types of offshore platforms for specific seawater depths are available. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In-place analysis for offshore platforms is essentially required to make proper design for new structures and true assessment for existing structures. The structural integrity of platform components under the maximum and minimum operating loads of environmental conditions is required for risk assessment and inspection plan development. In-place analyses have been executed to check that the structural member with all appurtenances has robustness and capability to support the applied loads in either storm condition or operating condition. A nonlinear finite element analysis is adopted for the platform structure above the seabed and the soil–pile–jacket interaction to estimate the in-place behavior of a typical fixed offshore platform. The analysis includes an interpretation of the dynamic design parameters based on the available site-specific data, together with foundation design recommendations for in-place loading conditions. The SACS software is utilized to calculate the natural frequencies, dynamic amplification factors, and the stresses at selected members, as well as their nodal displacements. The directions of environmental loads and water depth variations have important effects on the results of the in-place analysis behavior. The incidence angle of seismic waves is an essential parameter, where, for some crucial angles, the internal forces and the maximum deformations can be doubled or more in comparison with the ones corresponding to other, less crucial angles. Therefore, the incidence angle considerably affects the response quantities. The results confirm that the in-place analysis is quite essential for the reliable design of new offshore platforms and the assessment of existing offshore structures. [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]

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]

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.)

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]

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]

Structural intensity approach is introduced to study the crack detection for offshore platform in the paper. The Line Spring Model (LSM) of surface crack is proposed based on plate crack structure, and thus the relationship between the additional angle, displacement and crack relative depth is achieved. Besides, the concept of appended structure-borne sound intensity is introduced. The expression of appended structural intensity for crack damage is derived. By observing the input energy, distribution, transmission and vibration performance of structure intensity, evidence is provided for detection of crack location. Vibration analysis is conducted on the whole platform under multi environment load. Using the structural intensity approach, the crack is detected on the key point easily. Moreover, the K-shape welded pipe point is detected using structural intensity approach, and the crack can be detected accurately. Therefore, development structural intensity approach would be extremely useful to spread out technologies that can be applied for offshore platform crack detection accurately. [ABSTRACT FROM AUTHOR]

The stabilization problem of two or three parallel operating diesel gas generators as part of autonomous electric energy system is considered in the article. This system working conditions are considered as a part of mountainous self-contained platform where ship electric mains load sharp changes are unsuitable for existing diesel gas generators automatic control systems because the latter are characterized by rotating speed high instability. Rotating depends on generator loads (torque), hence the diesel gas generator frequency controller adjustment must be improved depending on its operational conditions. The drilling rig autonomous electric energy system operation analysis allowed establishing that commutation processes based on loads loss and connection cause mains voltage and frequency fluctuations. Their spectrum is of the same frequency range as DGGS rotating oscillation spectrum, this conduce to power oscillations onset between parallel-working generators. On the conducted experiments basis the diesel gas generator speed controller adjustment factors values, which provide the best transient process with specified power, were obtained. It is seen from conducted analysis that the controller adjustment should be conducted under minimum power rather than normal power. It was demonstrated that however the load increment will cause stability margin increase. On the decibel-log frequency characteristic (DLFC) method basis, the analytical dependence between diesel engine and controller parameters was established. This dependence allows system oscillation acceptable degree establishing. [ABSTRACT FROM AUTHOR]

When fire occurs in an offshore platform, evacuation plays a vital role in safeguarding the evacuees' lives. How to efficiently evacuate to minimize the loss of life is a dynamic problem, requiring a continuing research effort with changing technologies. In this research, a dynamic optimisation model is proposed to determine the optimized evacuation route in the fire scenarios of offshore platforms. Firstly, the road network model of an offshore platform is built in a Geographic Information System (GIS) environment based on the data from a real drilling platform. Secondly, drilling platform fires are simulated using Fire Dynamics Simulation (FDS), and then the fire simulation data is input into the proposed road network model. Thirdly, the traditional Ant Colony Optimisation (ACO) Algorithm is improved by considering the influence of fire on evacuation to study the impact of high temperature, smoke and toxic gases on evacuation. Next, the improved route optimisation algorithm and a road network model of the offshore platform are integrated to formulate a dynamic route optimisation model for evacuation in fire scenarios. Finally, a case study is conducted to demonstrate the model on a drilling platform of Nan Hai in China. The results reveal that the equipment area around the fire source on the lower deck is mostly affected by the smoke. It is validated that the proposed model can be used to optimize the evacuation route to guide evacuees avoid the hazardous area according to the dynamic spread of smoke. This study can provide fast real-time guidance for the trapped evacuees during the evacuation process on offshore platforms by considering the influence of fire on evacuation. • The road network model of an offshore platform is built in a GIS environment. • Drilling platform fires are simulated by FDS, and then the fire data is input into the proposed road network model. • The traditional Ant Colony Algorithm is improved by considering the influence of fire on evacuation. • The improved route optimisation algorithm and the road network model are integrated to propose the dynamic route optimisation model for evacuation in the fire scenarios of offshore platforms. • The scientific novelty is that the proposed dynamic route optimisation model can visualize the real time impact of dynamic fires on evacuation route and optimize the evacuation route. [ABSTRACT FROM AUTHOR]

Abstract: We explore the applicability of exergy analysis as an evaluation and monitoring tool for the oil and gas processing on an offshore platform. A real production day on a particular North Sea platform is analysed. A process flowsheet is simulated using measured process data. We distinguish between temperature based exergy, pressure based exergy and the mixing part of the chemical exergy. It is shown that physical exergy in the material streams mainly is pressure based exergy, and most exergy destruction is related to decrease or increase in pressure. The sub-processes with most destructed exergy are the production manifold (4600 kW), the recompression train (4150 kW) and the reinjection trains (10,400 kW). At this platform 260 kW separation work is done, where a considerable part is done in the compression trains in addition to in the separation train. The specific power consumption is 179 ± 3 kWh/Sm3 and the exergetic efficiency is 0.13 ± 0.02. We propose measures to decrease exergy destruction, and that exergy analysis should be taken into regular use by the oil and gas industry. This study serve as a showcase on how to do an exact analysis of an existing offshore platform using measured process data. [Copyright &y& Elsevier]

A simple method is used to predict damping and natural frequencies of a fixed offshore platform subjected to wind-generated random waves using its stationary response. The method also predicts the reaction forces and bending moment at the foundation of the platform. The method uses the random decrement signature as a tool to identify the parameters in the equation of motion. Excellent agreements were obtained between the estimated and actual values of the parameters as well as for the reaction and moment at the platform foundation. The method can be applied without any interruption to the operation of the offshore structure. The method is easy to apply and uses inexpensive motion measurement instruments. The estimated forces and bending moments can be used as a tool for an on-line foundation check. A study on the limitations of applying the random decrement technique is also presented. [ABSTRACT FROM AUTHOR]

Motivated by soial and environmental reasons, water scarcity has become a global top agenda item. Egypt is one of the countries suffering from an acute shortage of freshwater. A promising novel and efficient solution to overcome Egypt's freshwater shortage, especially in remote coastal areas far from the national grid of freshwater and electricity, is a mobile floating desalination plant (FDP) powered by offshore renewable energy. The proposed new FDP concept powered by an offshore wind turbine needs a special floating platform to provide enough buoyancy to support the weight of the desalination plant and to restrain the six degrees of freedom motions within an acceptable operational limit for a wind turbine. Based on hydrodynamics, the main objective of this study is to select the suitable offshore platform that can meet the novel FDP concept operation's requirements at a specific deployment location in Egypt. Determining the safe natural frequencies zone necessitates taking into account the new FDP concept operation constraints and the Egyptian environmental loads to select platform far from the dynamic amplifications responses in the structure. Numerical modelling results show that the cylindrical platform with a heave plate configuration demonstrated the best dynamic and static performance for Egypt. • A novel mobile Floating Desalination Plant (FDP) is proposed for Egypt. • FPD is powered by offshore renewable energy. • The most suitable offshore platform is selected by performing numerical analysis. • The cylindrical platform with heave plate configuration demonstrated the best performance. [ABSTRACT FROM AUTHOR]

For the vibration of long-served offshore platforms induced by working equipment, it is very difficult to determine the relevant parameters such as structural stiffness, mass and exciting loads accurately. In order to determine the parameters reasonably, a comprehensive vibration testing was carried out to learn the general vibrating features on the offshore platform by a total of 51 measured points distributed on different decks of a 15-year platform. The measurement showed that the induced vibration covers multiple modes with a range of frequencies because of the complexity of the platform structure. Therefore we introduced average amplitude of vibrating displacement at each measurement point to define its vibrating strength. With the measured results of the vibration, a finite element model of the platform with explicit solution was set up to simulate the vibration of the platform. The natural frequencies and average amplitudes at different locations were set as the target values to determine the unknown mass and exciting load in an updating procedure. The results of the modified model have a good agreement with the target values, which indicated that the modified model is reliable and the updating method for determining unknown parameters in a complex structure is feasible. • Carry out comprehensive in-situ measurementand simulation of vibration response on along-served offshore platform. • Determine the vibration source of a complicatedstructure in a complex environment based onin-situ vibration response. • Propose a new updating method for FE model toderive the unknown structural parameters and the excited load for the long-serviced offshoreplatform. [ABSTRACT FROM AUTHOR]

Ding, N., 2020. Vibration analysis of offshore oil and gas platform mechanical equipment. In: Gong, D.; Zhang, M., and Liu, R. (eds.), Advances in Coastal Research: Engineering, Industry, Economy, and Sustainable Development. Journal of Coastal Research, Special Issue No. 106, pp. 633–637. Coconut Creek (Florida), ISSN 0749-0208. Based on the case of a shallow-water drilling platform, this article focuses on the vibration principle and vibration-control strategy for oil and gas platforms. Through the analysis of ANSYS and field-measured data, this research obtained several causes for violent vibrations of platforms and puts forward countermeasures to prevent platform accidents from vibration. Drilling platforms belong to offshore operation, which have great theoretical risks. In the work of substations, railways, and mines on land, the design of the operation sheet and dispatching instruction are strictly evaluated, and there should be similar attention to dispatching work of drilling platform. [ABSTRACT FROM AUTHOR]

In offshore platforms, effective gas detection system is an essential layer of protection for preventing potential gas release accident from turning to fire and explosion disasters. However, according to statistics the actual efficiency of gas detection systems is still unsatisfactory. In this work, a stochastic programming (SP) approach is proposed to arrange gas detectors in optimal places. Combined with meteorological data and the hydrocarbon releases (HCR) database, the equipment leakage scenarios are envisaged. The computational fluid dynamics (CFD) commercial code Ansys-Fluent is used to simulate selected scenarios and predict the consequences. With the objective of minimizing the cumulative risk of gas leakage scenarios, a stochastic mixed-integer linear programming formulation based on p-median value theorem is proposed. Then particle swarm optimization (PSO) algorithm is used to solve the optimization model. The gas detector placement optimization on an oil drilling production platform (DPP) is also carried out as a case example. This methodology can be used in the design phase of offshore platform and can hopefully enhance the performance of the gas detection system. • A stochastic programming approach is proposed for the optimization of gas detectors' placement in offshore platform. •An effective technique combining the offshore hydrocarbon releases database is provided to scientifically identify potential leakage scenarios and improve risk characterization. •The complete accident scenario set (CASS) is constructed by considering the leakage sources and wind fields to enhance the performance of the gas detection system. •This methodology can be used in the design phase of offshore platform, giving the high efficiency detector layout scheme on the basis of satisfying the standards and achieving optimal risk control effect of the gas detection system. [ABSTRACT FROM AUTHOR]

Offshore drilling raises the issue of disposal of platforms at the end of their productive cycle and re-use as artificial reefs has been proposed. The wreck of the “Paguro” drilling platform, which sank in the northern Adriatic Sea in 1965, offers the opportunity to study the performance of offshore structures as artificial reefs in a region where this solution has not been explored before. We provide a description of the macrobenthic assemblages present at the wreck at different sites and at different depths, based on destructive and photographic sampling. Results show that the wreck has been colonized by a rich and diversified fauna. Primary space has been dominated by mussels and oysters, which provide suitable habitats for a variety of benthic invertebrates. Assemblages vary among sites, species richness is greatest at those sites facing prevailing currents. Distribution patterns vary vertically, evenness (Hill's N10) decreasing significantly with depth. It is argued that the results contribute to the background knowledge required in rigs-to-reefs programmes. Copyright 2002 International Council for the Exploration of the Sea. Published by Elsevier Science Ltd. All rights reserved. [ABSTRACT FROM PUBLISHER]