Flexible Riser Fatigue Procedure Using a Long Term Distribution of FPSO’s Heading Direction

2002 ◽  
Author(s):  
Carlos Alberto Duarte de Lemos ◽  
Murilo Augusto Vaz
Keyword(s):  
Environmental Conditions ◽  
Environmental Data ◽  
Mooring Lines ◽  
Fatigue Design ◽  
Beam Seas ◽  
Heading Direction ◽  
Campos Basin ◽  
Directional Waves ◽  
Flexible Risers

The intensive use of FPSOs in Campos Basin, offshore Brazil, has demanded more attention on the fatigue design of flexible risers. Field experience and a new set of environmental data collected in the last years have shown a large number of swell waves reaching the floating units in quartering and beam seas, which has amplified the motions at the risers’ top connections. Hence, it is necessary to evaluate the occurrence probability of wave heading direction relative to the vessel, especially for beam seas, but also noting the probability increase of quartering seas considering the existence of bi-modal and bi-directional wave spectra. The simultaneous environmental conditions — wind, current and bi-directional waves (sea and swell) — registered in Campos Basin, were condensed in a few hundreds environmental conditions to enable its utilization on a simulation program, where the FPSO, mooring lines and risers were modeled to obtain the mean heading and offsets. This new set of FPSO headings were then used to define a new proposal of load conditions to evaluate the fatigue life of flexible risers. This new procedure was then applied to a case study for the FPSO P-33 employing the tools available at PETROBRAS research center. The results have confirmed the importance of beam and quarter seas, which respectively cause heavy roll and vertical motions at the turret and then, affecting the fatigue of the risers.

Comparative Study on Fatigue Damage Assessment of a Structure Member in a Bulk Carrier Using Various Environmental Conditions

2019 ◽  
Author(s):  
Fredhi Agung Prasetyo ◽  
Naoki Osawa ◽  
Mohammad Arif Kurniawan ◽  
Siti Komariyah
Keyword(s):  
Fatigue Damage ◽  
Environmental Conditions ◽  
Damage Assessment ◽  
North Atlantic Ocean ◽  
Environmental Condition ◽  
Scatter Diagram ◽  
Sea State ◽  
Fatigue Design ◽  
Design Life

Abstract Specific design life could be identified by using fatigue damage assessment in the structure engineering field as well as in the maritime sector. Fatigue assessment is one of the assessments to be conducted during review of ship structure design. Fatigue assessment of ship structural member is mainly conducted based on specific environmental condition. In general, specific environmental condition, which is provided by Classification Society rules, is a long term sea-state data of North Atlantic Ocean. The wave scatter diagram presents the tabulation of a long term data of sea state history in the specific ocean. Therefore, a realistic encounter of wave scatter diagram is essential to simulate the variation of wave loadings applied on the ship structure in determination of fatigue design life. Since the application of North Atlantic ocean environmental condition is commonly used by major Classification societies, this condition might give the substantial deterioration on the fatigue design life of the ship that specially operate only in specific ocean area, i.e. South East Asia area. In this work, the wave scatter diagram of various environmental conditions is chosen and the statistical characteristic is compared. The wave load sequence that is used on the fatigue damage assessment are generated by using the concept of storm model, so that the changing nature of sea state could be emulated as in real ocean. Fatigue damage of a structure member of 220 meter Bulk Carriers is calculated based on various environmental conditions.

scholarly journals Long-Term Patterns of Amphibian Diversity, Abundance and Nutrient Export from Small, Isolated Wetlands

Diversity ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 598
Author(s):  
Carla L. Atkinson ◽  
Daniel D. Knapp ◽  
Lora L. Smith
Keyword(s):  
Life History ◽  
Environmental Conditions ◽  
Life History Traits ◽  
Community Dynamics ◽  
Animal Movement ◽  
Nutrient Content ◽  
Environmental Data ◽  
Spatial And Temporal Variability ◽  
Isolated Wetlands

Seasonally inundated wetlands contribute to biodiversity support and ecosystem function at the landscape scale. These temporally dynamic ecosystems contain unique assemblages of animals adapted to cyclically wet–dry habitats. As a result of the high variation in environmental conditions, wetlands serve as hotspots for animal movement and potentially hotspots of biogeochemical activity and migratory transport of nutrient subsidies. Most amphibians are semi-aquatic and migrate between isolated wetlands and the surrounding terrestrial system to complete their life cycle, with rainfall and other environmental factors affecting the timing and magnitude of wetland export of juveniles. Here we used a long-term drift fence study coupled with system-specific nutrient content data of amphibians from two small wetlands in southeastern Georgia, USA. We couple environmental data with count data of juveniles exiting wetlands to explore the controls of amphibian diversity, production and export and the amphibian life-history traits associated with export over varying environmental conditions. Our results highlight the high degree of spatial and temporal variability in amphibian flux with hydroperiod length and temperature driving community composition and overall biomass and nutrient fluxes. Additionally, specific life-history traits, such as development time and body size, were associated with longer hydroperiods. Our findings underscore the key role of small, isolated wetlands and their hydroperiod characteristics in maintaining amphibian productivity and community dynamics.

Ultra-Deepwater Floating Platforms Simulation on SPAR Realistic Marine Virtual Environment System

2003 ◽  
Author(s):  
Gerson Gomes Cunha ◽  
Luis Augusto Petrus Levy ◽  
Maria Ce´lia Santos Lopes ◽  
Luiz Landau
Keyword(s):  
Environmental Conditions ◽  
Large Scale ◽  
Scientific Data ◽  
Design System ◽  
Floating Platform ◽  
Visual Effects ◽  
Mooring Lines ◽  
Campos Basin ◽  
Scale Design ◽  
Floating Platforms

This paper presents a new system for offshore floating petroleum platforms design and simulation using virtual reality technology. Environmental conditions and visual effects were introduced together the analysis results to build a realistic experience. The system integrates the capabilities of a large scale design system PROSIM, for design and evaluation of floating structures, mooring lines and rigid or flexible risers under wave, wind and current effect; and SPAR system, for realistic visual effects and environmental conditions representation to enhance the visual perception and phenomenon understanding. It will be presented a real case usage of the system in the project of new floating platform with wave, wind and terrain data of the Campos Basin (Brazilian biggest reservoir). The real-time simulation of floating systems is not new, but until today only scientific aspects were considered besides visual appeal. The association of artistic elements only used on movies and games are introduced in real engineering simulation creating a new way of understanding and interacting with this scientific data.

Long-Term Analysis Applied to Mooring Systems Design

2020 ◽  
Author(s):  
Pedro Seabra ◽  
Luis Volnei Sudati Sagrilo ◽  
Paulo Esperança
Keyword(s):  
Time Domain ◽  
Environmental Conditions ◽  
Systems Design ◽  
Environmental Data ◽  
Coupled Analysis ◽  
Offshore Structure ◽  
Short Term ◽  
Extreme Response ◽  
Term Analysis

Abstract Nowadays, the most used methodology to predict line tensions is the short-term coupled analysis, where the mooring system responses are obtained by a time-domain analysis for only some specific design combinations of extreme environmental conditions. This mooring analysis demands certain considerations and it is not the best way to obtain the offshore structure responses. The advances in both quantity and quality of collected environmental data and the increase of the computers processing power has enabled to consider the approach of more accurate long-term methodologies for mooring systems design. This paper proposes a numerical/computational procedure to obtain the extreme loads (ULS) acting on offshore platforms’ mooring lines. The work is based on the methodology of long-term analysis, employing a 10-yr long short-term environmental dataset of 3-h sea-states, where each short-term environmental condition is composed of the simultaneously observed environmental parameters of wave (sea and swell), wind and current. The methodology is applied to the analysis of three different mooring systems: a) spread-moored FPSO, b) Semi-Submersible platform and c) turret-moored FPSO. The Bootstrap approach is employed in order to take into account the statistical uncertainty associated to the estimated long-term most probable extreme response due to the limited number of short-term environmental conditions. The work was carried out using Dynasim software [1] to generate the time domain tension time series, which were later post-processed by using computational codes developed with Python software. Longer short-term numerical simulations lengths than the short-term period (3-h) have been investigated in order to understand the influence of this parameter on the final extreme long-term top tensions.

Flexible Riser Fatigue Evaluation for FPSO’s in Bi-Directional Sea Spectra

2003 ◽  
Author(s):  
Carlos Alberto Duarte de Lemos ◽  
Murilo Augusto Vaz ◽  
Marcos Queija de Siqueira
Keyword(s):  
Operational Experience ◽  
Flexible Riser ◽  
Mooring Lines ◽  
Directional Spectrum ◽  
Campos Basin ◽  
Calculation Methodology ◽  
Flexible Risers ◽  
Fatigue Evaluation ◽  
Simplified Procedure ◽  
The Impact

The fatigue calculation methodology applied to flexible risers connected to FPSOs, offshore Brazil, is based on a simplified procedure considering a deterministic regular wave approach and a wave heading distribution supported by past operational experience with semi-submersible platforms. However the utilization of deterministic waves approach does not necessarites guarantee the consideration of the worst sea conditions, and the weathervaning capability of those systems are usually not accounted for when non-collinear wave, wind and current are present. A new procedure is being evaluated considering an integrated model for ship, mooring lines and risers to define the distribution of ship headings for fatigue analysis using an irregular bi-directional sea approach. The impact on a flexible riser’s fatigue life will be evaluated when a new ship heading distribution with irregular bi-directional spectrum is presented for the case of a FPSO with bow turret in operation at the Marlin Field offshore Campos Basin.

Riser Top Loads on Turret Moored FPSO

2009 ◽  
Author(s):  
Felipe de Arau´jo Castro ◽  
Carlos Magluta ◽  
Gilberto Bruno Ellwanger
Keyword(s):  
Production Systems ◽  
Wind Waves ◽  
Model Tests ◽  
Structural Damping ◽  
Mooring Lines ◽  
Load Variations ◽  
Campos Basin ◽  
Loading Case ◽  
Flexible Risers ◽  
Important Design

In the Campos Basin, offshore Brazil, catenary flexible risers are extensively used in marine production systems. One of the most important design phases of these systems is the riser extreme top load analysis, which provides results for riser and accessory designs as well as input for structural analysis of platform supports. In addition to the riser’s characteristics (weight, diameter, structural damping, axial and bending stiffness), riser top loads depend on several other factors, such as platform static and dynamic behavior, including the collective effect of lines (mooring lines and risers) drag and damping, platform motion, connection support position and environmental loading cases. This study is based on the results from a model test and numerical analysis of a typical turret moored FPSO system, with catenary risers and mooring lines. This test was programmed to evaluate the consequence of each of the above mentioned parameters on flexible riser top loads. Model tests were performed in the MARIM (Maritime research Institute Netherlands) wave tank to represent the offshore system in 850 meter water depth and included loading case tests combining wind, waves and current in different relative directions (collinear, crossed and transversal). The analysis of the model tests results indicated significant variations in the platform behavior, when the drag and damping generated by the risers and mooring lines were taken into account. Additional analyses were performed, based on numerical simulations of the top load variations (axial, shear tension and moment), induced by movement changes (added drag and damping caused by risers and mooring lines) and to evaluate the influence of vessel heading on top load results.

Comprehensive Downtime Analysis of DP-Assisted Offloading Operation of Spread Moored Platforms in Brazilian Waters

2013 ◽  
Author(s):  
Diego C. Corrêa ◽  
Allan C. de Oliveira ◽  
Eduardo A. Tannuri ◽  
Sergio H. Sphaier
Keyword(s):  
Risk Analysis ◽  
Environmental Conditions ◽  
Minimum Distance ◽  
Substantial Reduction ◽  
Safety Zone ◽  
Positioning Systems ◽  
Campos Basin ◽  
Static Calculation ◽  
Green Zone

Oil offloading from Spread Mooring System (SMS) FPSO is usually done by means of a dynamically positioned shuttle tanker (DPST) in tandem configuration. The ST receives the oil pumped by the FPSO from a bow or stern offloading station, and the operation may take up to 3 days. In order to minimize the risks associated with the operation, the shuttle tanker (ST) should be kept within a safety zone with respect to the FPSO, which is usually given as a minimum distance between the two ships and an aperture angle from the FPSO centerline. In order to guarantee the tanker position during the whole operation, the operation must be performed with tankers provided with DP (dynamic positioning) systems. Since SMS FPSOs may be not aligned to the environmental forces, keeping the shuttle tanker in position may be a hard task for the DP system, depending on the environmental conditions. There are non-rare situations in which the ST must be disconnected and the operation interrupted. The present paper applies a methodology based on static calculation of DP capacity for evaluating the downtime of such offloading operation. The three generations of DP tankers applied in Brazilian waters are considered. Santos and Campos Basin long-term (8-year) environmental conditions (current, wind, local-sea and swell) are used in the downtime calculation. The main objective is to provide a quantitative tool to analyze important parameters of the operation, in order to support some redefinitions in the operational procedure adopted by Petrobras. The main parameters are: the angle of the safe green-zone defined from the FPSO centerline, the installed DP power, the necessity of bow and stern offloading stations in the FPSO, among others. The results indicated that due to the large variation of wave-wind conditions along the year, both offloading stations are indeed necessary, since the ST can avoid the conditions in which it is pushed towards the FPSO. The results also indicated that incrementing the angle that defines the green-zone substantially decreases the offloading downtime. However, such decision also depends on a comprehensive risk analysis, since in that case the ST may be kept in a perpendicular position related to the FPSO. The risk analysis is beyond the scope of the present work. The DP power specified for the ST generations 2 and 3 are shown to be quite adequate, since it is demonstrated that increasing this power will not lead to a substantial reduction in the downtime.

Protected Areas: offering security to whom, when and where?

2016 ◽  
Vol 43 (2) ◽  
pp. 172-180 ◽  
Author(s):  
ALICE B. KELLY ◽  
A. CLARE GUPTA
Keyword(s):  
Protected Areas ◽  
Environmental Conditions ◽  
Protected Area ◽  
Spatial Scales ◽  
Local Population ◽  
Well Being ◽  
Economic Context ◽  
Term Management ◽  
Over Time

SUMMARYThis study considers the issue of security in the context of protected areas in Cameroon and Botswana. Though the literature on issues of security and well-being in relation to protected areas is extensive, there has been less discussion of how and in what ways these impacts and relationships can change over time, vary with space and differ across spatial scales. Looking at two very different historical trajectories, this study considers the heterogeneity of the security landscapes created by Waza and Chobe protected areas over time and space. This study finds that conservation measures that various subsets of the local population once considered to be ‘bad’ (e.g. violent, exclusionary protected area creation) may be construed as ‘good’ at different historical moments and geographical areas. Similarly, complacency or resignation to the presence of a park can be reversed by changing environmental conditions. Changes in the ways security (material and otherwise) has fluctuated within these two protected areas has implications for the long-term management and funding strategies of newly created and already existing protected areas today. This study suggests that parks must be adaptively managed not only for changing ecological conditions, but also for shifts in a protected area's social, political and economic context.

Long-term environmental data explain better the abundance of the red octopus (Octopus maya) when testing the niche centroid hypothesis

2021 ◽  
Vol 544 ◽  
pp. 151609
Author(s):  
Luis Enrique Ángeles-González ◽  
Enrique Martínez-Meyer ◽  
Carlos Rosas ◽  
Paulina Valeria Guarneros-Narváez ◽  
Jorge A. López-Rocha ◽  
...  
Keyword(s):  
Environmental Data ◽  
Octopus Maya

Analysis of high yielding maize production - a study based on a commercial crop

2008 ◽  
Vol 48 (3) ◽  
pp. 296 ◽  
Author(s):  
C. J. Birch ◽  
G. McLean ◽  
A. Sawers
Keyword(s):  
Retrospective Analysis ◽  
Environmental Conditions ◽  
Sowing Date ◽  
Plant Population ◽  
Higher Plant ◽  
Maize Crop ◽  
Wide Range ◽  
Commercial Crop ◽  
Reduced Temperature

This paper reports on the use of APSIM – Maize for retrospective analysis of performance of a high input, high yielding maize crop and analysis of predicted performance of maize grown with high inputs over the long-term (>100 years) for specified scenarios of environmental conditions (temperature and radiation) and agronomic inputs (sowing date, plant population, nitrogen fertiliser and irrigation) at Boort, Victoria, Australia. It uses a high yielding (17 400 kg/ha dry grain, 20 500 kg/ha at 15% water) commercial crop grown in 2004–05 as the basis of the study. Yield for the agronomic and environmental conditions of 2004–05 was predicted accurately, giving confidence that the model could be used for the detailed analyses undertaken. The analysis showed that the yield achieved was close to that possible with the conditions and agronomic inputs of 2004–05. Sowing dates during 21 September to 26 October had little effect on predicted yield, except when combined with reduced temperature. Single year and long-term analyses concluded that a higher plant population (11 plants/m2) is needed to optimise yield, but that slightly lower N and irrigation inputs are appropriate for the plant population used commercially (8.4 plants/m2). Also, compared with changes in agronomic inputs increases in temperature and/or radiation had relatively minor effects, except that reduced temperature reduces predicted yield substantially. This study provides an approach for the use of models for both retrospective analysis of crop performance and assessment of long-term variability of crop yield under a wide range of agronomic and environmental conditions.

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