General Recommendations From the Results of Reassessment of 21 Platforms in Bay of Campeche

2010 ◽  
Author(s):  
Partha Chakrabarti ◽  
Juan de Dios de la O.
Keyword(s):  
Fatigue Life ◽  
Service Life ◽  
Oil And Gas ◽  
Fatigue Behavior ◽  
Life Extension ◽  
Individual Member ◽  
Inspection Planning ◽  
Natural Period ◽  
Oil And Gas Exploration ◽  
Structural Weakness

Pemex Explorac´ion y Produccio´n (Pemex) owns and operates several fields for oil and gas exploration in the Bay of Campeche located in the south Gulf of Mexico. In order to meet the growing demand for oil and natural gas it was necessary to extend the service life for many existing platforms by at least another 15 to 30 years. To ensure a safe operation throughout this period, thorough and systematic reassessment studies needed to be conducted leading to the identification of any structural weakness. Finally, to control the fatigue behavior of the welded joints, risk based inspection planning (RBI) was adopted to ensure extended service life. In these reassessment studies the ultimate strength of the platforms is evaluated through nonlinear pushover analyses as a part of condition assessment. Spectral fatigue analyses are performed to identify the fatigue sensitive joints. This is followed by redundancy analyses, assuming that one individual member at a time becomes ineffective given a weld fatigue failure at the joint. For the inspections aimed to control the development of predictable degradation such as fatigue crack growth, the inspection efforts can be targeted such that the risks implied by the degradation are kept within acceptable limits. This is done through a risk based inspection planning strategy. The analytical aspects for this approach were discussed in previous papers on the subject by the authors. The current paper presents the overall results of 21 platforms taken up for a recent study and discusses the trends in view of broad parameters such as water depth, loading, structural arrangement. These structures include drilling, production, gathering and living quarter platforms. The platforms are located in various assets in water depths ranging from 40 to 90m, have different configurations with 3, 4 and 8 legged jackets, they also support different deck weights. In the present paper overall results of the study performed for 21 platforms are presented. The platforms have been classified in terms of platform type, number of legs, framing pattern, leg diameter etc. The results for strength of the platforms obtained from pushover analyses, and fatigue life are analyzed in light of the classification parameters. The differences in the platform characteristics such as stiffness, wave loading and natural period are discussed along with their implications to strength and fatigue life. Inspection requirements are also interpreted in the light of these global parameters. Finally, some general recommendations are made for design of jackets keeping in view the overall behavior and inspection requirements. It is believed that if the recommendations are followed in the initial design there would be benefits in the future for inspection, maintenance, and repair and possible life extension increasing their economic return.

Effect of Joint Behavior on the Reassessment of Fixed Offshore Platforms in the Bay of Campeche, Mexico

2005 ◽  
Author(s):  
Partha Chakrabarti ◽  
Adinarayana Mukkamala ◽  
Ibrahim Abu-Odeh ◽  
Juan de Dios de la O. Rami´rez
Keyword(s):  
Fatigue Life ◽  
Service Life ◽  
Oil And Gas ◽  
Gas Production ◽  
Strength Analysis ◽  
Offshore Platforms ◽  
Inspection Planning ◽  
Oil And Gas Production ◽  
Joint Flexibility ◽  
Joint Behavior

Pemex Exploration y Produccio´n owns and operates several fields in the Bay of Campeche, located in the south Gulf of Mexico, for oil and gas production. Many of these fixed offshore platforms were built during the 70s and 80s and have already exceeded their design service life. To meet the growing demand for oil and natural gas it was found economic to extend the service life for these platforms by at least another 15 to 30 years. To meet this extended service life, thorough and systematic reassessment studies need to be conducted leading to identification of any structural weakness and possible locations of fatigue problems. To extend the fatigue life of the welded joints, inspections are required to be performed according to a risk based inspection planning procedure. As a part of the reassessment study non-linear pushover and spectral fatigue analyses are conducted. The effect of joint behavior, viz. the local joint flexibility and strength, on the structural ultimate capacity and fatigue life is discussed in this paper. In conventional analysis the tubular joints are assumed to be rigid and the flexibility effects due to shell deformations are ignored. In this present paper, the effect of the joint behavior is included in the analysis and its implications on the results are discussed. For the ultimate strength analysis both API and MSL formulations for the load-deformation behavior of the joint are studied and compared. For the fatigue analyses, local joint flexibility modeling using Buitrago’s formulation is used. Results including and excluding these effects are compared. Effect of grouting of the joint is also studied. Comprehensive results of the study for a number of platforms, which cover the categories of Drilling, Production, Gathering and Habitation, are presented. The effects of local joint flexibility and joint strength on structural behavior have been recognized to be important in the recent publications of the recommended practices and the codes such as the API RP 2A. However, comprehensive discussions and the results of application of these aspects are rare in the published literature. This paper addresses these issues and presents the results of a large number of platforms of different configurations, indicates some noticeable trends and suggests some general conclusions.

Structural Impact in FPSO Life Extension: A Class Perspective

2013 ◽  
Author(s):  
Christiane L. Machado ◽  
Sudheer Chand
Keyword(s):  
Service Life ◽  
Oil And Gas ◽  
Structural Response ◽  
Oil And Gas Industry ◽  
Environmental Data ◽  
Life Extension ◽  
Element Analysis ◽  
Actual Performance ◽  
Remaining Service Life ◽  
The Impact

The Offshore Oil and Gas Industry has converted a large number of units from trading tankers and carriers into Floating Production, Storage and Offloading units (FPSOs). Several of these have been moored offshore Brazil during the last 15 years. Following the discovery of offshore pre-salt fields some years ago, demand for FPSOs has increased, and the forecasts for productive field lives have grown. The result of these developments is the need to extend the service lives of existing FPSOs. The main aim of this study is to investigate FPSO structural response to environmental conditions and functional loads, considering the actual available tools for numerical simulations and Rule requirements, which currently are basic requirements for design review for Classification. The procedure was developed from one selected FPSO converted from a trading Very Large Crude Carrier (VLCC) tanker approximately 15 years ago and includes investigation of the impact on hull behavior comparing the motion analyses of the production unit under environmental data and software capabilities available at the period of conversion and actual performance: variances in the environmental (sea scatter diagrams) datasets; updates to Classification requirements for defining offloading conditions, environmental loads, acceptance criteria and remaining fatigue life (RFL); and incorporating the most recent gauged thickness for primary structure. The selected FPSO was evaluated according to prescriptive Rule requirements and also using finite element analysis, taking into account the previous conditions of Classification approval as well as the actual requirements and available data. Structural analysis included one global model and some local refined models to address strength, buckling and fatigue capacity of the typical portions/connections of the hull. The comparisons performed from the results of these analyses are a crucial step toward understanding the structural capacity of the FPSO at the conversion stage, its performance during the last 15 years, and its remaining service life. Differences were tabulated and evaluated so that a more precise level of uncertainty could be achieved for predicting the estimated remaining service life, and consequently, a new and dedicated approach to investigate the existing FPSO fleet is being generated.

scholarly journals Numerical Evaluation of Structural Safety for Aged Onshore Wind Foundation to Extend Service Life

2020 ◽  
Vol 10 (13) ◽  
pp. 4561
Author(s):  
Youn-Ju Jeong ◽  
Min-Su Park ◽  
Sung-Hoon Song ◽  
Jeongsoo Kim
Keyword(s):  
Fatigue Life ◽  
Service Life ◽  
Safety Evaluation ◽  
Life Extension ◽  
Structural Safety ◽  
Material Strength ◽  
Design Strength ◽  
Onshore Wind ◽  
Service Period ◽  
Service Life Extension

In this paper, for the case of “service life extension” with the same capacity for wind turbines, a structural safety evaluation was carried out to determine whether to extend the service life of the aged foundation. As a result of this study, it was found that the aged foundation satisfies the structural safety of material strength, ultimate strength, fatigue life, and serviceability up to the present. Although the in-service period has been over 16 years, it has been shown that the material properties of concrete have exceeded the design strength, and no significant material deterioration has occurred. Also, structural safety could be evaluated more realistically based on actual concrete properties. In particular, it has been shown that it has a fatigue life of 40 years or more, so service life can be extended. It is expected that the methodology used in this paper will be useful not only for structural safety evaluation of the foundation in service, but also for decision-making for extending the service life. Furthermore, a more technical approach should be explored by many researchers in the future.

Applying Digital Technologies Beyond Design Life

2021 ◽  
Author(s):  
Luiz Paulo Feijo ◽  
Suqin Wang ◽  
Christiane Machado
Keyword(s):  
Fatigue Life ◽  
Service Life ◽  
Digital Technology ◽  
Predictive Analytics ◽  
Life Extension ◽  
Structural Behaviour ◽  
Structural Evaluation ◽  
Design Service Life ◽  
Remaining Fatigue Life ◽  
Extension Process

Abstract This paper focuses on Floating Production Installations, which are assets designed based on site-specific environmental conditions to determine their design service life. The longevity of these assets depends on the fatigue aspects related to the structural elements and mooring systems. Among the challenges involving the continued services of ageing assets is the integrity of these elements. When an asset reaches its end of design service life, Operators often decide to undergo a life extension process for safe continued operations. Alife extension process generally includes three phases: investigation, determination and implementation. Following a baseline inspection to determine the present conditions of the structures, engineering assessments are to be carried out to evaluate the fatigue damage through the lifecycle of the installation and therefore determine the remaining fatigue life. Collecting information to execute these assessments is challenging and can be automated with the use of digital technology. Digital tools allow an accurate collection of data, providing a continuous evaluation of the remaining fatigue life and supporting an informed decision-making process. Observing the operation of several aging assets and their structural behaviour, the parameters to be measured during the installation's lifecycle have been identified along with other aspects that also contribute to the determination of its continued service. The recommended data acquisition for relevant measurements is summarized in this paper. The application of sensors and monitoring systems on the installations allows measuring these parameters on a continuous basis, and consequently, Operators are able to determine the degradation pattern that the structure is subject to. An estimation of the remaining fatigue life can be achieved by using predictive analysis, which, along with insights of the future expected corrosion, provides Operators the necessary basis to implement corrective measures and mitigations to avoid the occurrence of a failure. This paper offers an innovative, forward-looking technology that allies physics-based processes with digital technology, supported by predictive analytics and continuous structural evaluation, to assess the integrity of an offshore asset in support of safe continued services.

Service fatigue life and service calendar life limits of aircraft structure: aircraft structural life envelope

2016 ◽  
Vol 120 (1233) ◽  
pp. 1746-1762 ◽  
Author(s):  
Y. He ◽  
C. Li ◽  
T. Zhang ◽  
J. Liu ◽  
C. Gao ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Service Life ◽  
Life Prediction ◽  
Residual Life ◽  
Prediction Method ◽  
Life Extension ◽  
Aircraft Structure ◽  
Structural Repair ◽  
Service Life Extension ◽  
Service Environments

ABSTRACTThe service life of aircraft structure includes the fatigue life and calendar life. The Aircraft Structural Life Envelop (ASLE) is a safe and reliable life scope of aircraft structures in service. The specific steps to establish the ASLE are developed, and a residual life prediction method for aircraft structure under service environments is established by combining the ASLE with the Miner theory. Furthermore, a service life extension method of aircraft structure is proposed based on a scope extension of the ASLE, including methods based on reliability analysis and structural repair. Finally, an application example of the ASLE is presented.

Fatigue Life Extension of Offshore Structures by Ultrasonic Peening

2011 ◽  
Author(s):  
Luis Lopez Martinez
Keyword(s):  
Fatigue Life ◽  
Service Life ◽  
Fatigue Resistance ◽  
Structural Integrity ◽  
High Stress ◽  
Offshore Structures ◽  
Life Extension ◽  
Original Design ◽  
Ultrasonic Peening ◽  
Offshore Installations

The service life of offshore installations is limited by its structural integrity. Furthermore the structural integrity is mainly governed by the fatigue resistance of critical welded details. In a FPSO installation these details are among others pallet stools weld joints to deck structure and bulkheads/web frames weld connections to longitudinal in ballast tanks. ultrasonic peening can improve the fatigue resistance of welded joints. Fatigue test results shows an increase of four times for high stress ranges and up to ten times for high cycle fatigue. For specimens which have already consumed half of their fatigue life the treatment resets the clock to zero, as a minimum value. Consequently ultrasonic peening treatment was applied to several offshore installations on fatigue sensitive weld connections with the objective to extend the service life of the these. Finite Element Analysis carried out by classification societies for these offshore structures demonstrated critical fatigue lives for several weld connections. These weld connections were then treated by ultrasonic peening with the objective to extend their fatigue lives and by doing that reach the targeted service life for the installation. The successful application of the ultrasonic peening treatment was a pioneering work which involved several partners. A pilot project on a FPSO started in 2005 and the treated critical weld connections are still intact and show not sign of crack initiation despite the fact the calculations then showed shorter fatigue lives than the life span already consumed. As a result the same ultrasonic peening procedure has been proposed to be applied for other fatigue sensitive locations on the installation. Offshore installations around the world are reaching their original design life. Most of the operators chose to extend the service life of their assets rather than scrape them and build new. The reasons for that are: improved oil recovering techniques, time required to get a new build installation on site, environment concerns, wiser management of energy and resources among others. Therefore the Life Extension of Offshore Installations is a subject of current interest for the upstream industry.

Experimental and Numerical Investigation on the Effect of Varying Hull Shape Near the Water Plane on the Mathieu-Type Instability of Spar

2016 ◽  
Author(s):  
N. Senthil Kumar ◽  
S. Nallayarasu
Keyword(s):  
Oil And Gas ◽  
Operating Conditions ◽  
Scale Model ◽  
Experimental Investigations ◽  
Natural Period ◽  
Period Ratio ◽  
Oil And Gas Exploration ◽  
Wave Flume ◽  
Spar Platforms ◽  
Plane Area

Spar platforms have been used for oil and gas exploration in deep water for the past two decades. Spar experience low heave and pitch motions in operating conditions with its deep draft and large inertia. The heave motions can be large when encountered by long period swells. These resonant response leads to unstable motions due to heave-pitch coupling in spar platforms when the heave/pitch natural period ratio is 0.5, 1.0, 1.5 and 2.0, referred to as Mathieu-type instability. This instability can be avoided by changing heave or pitch natural periods, so that the heave-pitch coupling can be avoided. The buoy form Spar proposed in this study is a cylindrical hull with curved surface near the water plane. A classic Spar of 31 m diameter and deep draft buoy form Spars with 25 m and 20 m diameter at the water plane area have been considered. The moon pool diameter of 12.5 m and the displacement of 63000 tonnes are maintained for all Spars. The experimental investigations are conducted using 1:100 scale models in the wave flume. Numerical simulations have been carried out using panel method. The classic Spar experiences Mathieu-type instability, since the heave/pitch natural period ratio is 0.5. The heave natural period of the buoy form Spar is higher than the classic Spar by 24% and 72%. The heave/pitch natural period ratio of the first buoy form Spar with 25 m diameter at the water plane area is 0.667; hence the heave-pitch coupling is avoided. The second buoy form Spar with 20 m diameter at the water plane area does not experience Mathieu-type instability, even though the heave/pitch natural period ratio is 1.0. Also the heave natural period of the second buoy form Spar is 36s (3.6 s in scale model) which is much above the design wave period. The possibility of Mathieu-type instability is avoided in the Spar by varying the hull shape near the water plane.

A Study of Actuation Fatigue of Shape Memory Alloy

2012 ◽  
Author(s):  
Babatunde O. Agboola ◽  
Darren J. Hartl ◽  
Dimitris C. Lagoudas
Keyword(s):  
Fatigue Life ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Structural Reliability ◽  
Oil And Gas ◽  
Fatigue Tests ◽  
Test Environment ◽  
Oil And Gas Exploration ◽  
Reliability Issue ◽  
Set Up

The use of shape memory alloy (SMA) components as actuators is an attractive option for some aerospace, automotive, and oil and gas exploration applications, especially when installation volume is limited. Fatigue failures constitute a major structural reliability issue confronting industrial entities looking to employ this technology. Knowing and understanding the failure mechanism and resulting fatigue life of SMAs is therefore necessary and useful for design and certification prior to commercial use. An in-house developed experimental set-up based on Joule heating was used to complete a comprehensive set of fatigue tests on SMA actuators composed of a nickel-rich Nickel-Titanium (Ni-Ti) alloy subjected to cyclic thermomechanical loadings. A special forced convective cooling environment has been designed that utilizes compressed air and vortex tubes to maintain the test environment at a temperature well below the martensitic finish temperature. To thermally cycle the specimen, a time controlled scheme developed using LabVIEW was used. The system design allows full thermal cycling of large SMA specimens in approximately 80 seconds. Consequently, each test (comprised of thousands of cycles) takes weeks to be completed. Actuation fatigue life results of a complete test matrix for specimens undergoing full transformation at multiple stress levels are presented. Significant spread was observed in the number of cycles to failure for specimens under same isobaric loading across different choice of applied stress. Post-mortem microscopic observation of failed specimens suggested that failure is linked to cracks initiating within Ni3Ti precipitates. Observations reported further suggest that the failure of the specimen may not be due to plastic strain to failure.

Optimizing Analysis Methodology for HPHT Equipment

2019 ◽  
Author(s):  
J. Robert Sims ◽  
Jay Lefkowitz ◽  
Dave Dewees ◽  
Charles Becht
Keyword(s):  
Fatigue Life ◽  
Fracture Mechanics ◽  
Oil And Gas ◽  
Static Pressure ◽  
American Petroleum Institute ◽  
Element Analysis ◽  
Oil And Gas Exploration ◽  
Analysis Methodology ◽  
Mesh Density ◽  
Result Analysis

Abstract The American Petroleum Institute (API) is continuing to develop technical reports, guidelines and standards for the construction of high-pressure, high-temperature (HPHT) equipment for offshore oil and gas exploration and production. HPHT is considered to be equipment with a pressure rating greater than 103 MPa (15,000 psi) and/or a temperature rating greater than 177°C (350°F). One alternative in the evolving API standards is to use the analysis methodology in ASME Section VIII, Division 3, including fracture mechanics, for determination of the static pressure rating and the design fatigue life. However, detailed requirements for finite element analysis (FEA) parameters such as element type and mesh density are not specified. In addition, specific requirements for fracture mechanics analysis are not provided. This paper explores the effect of variations in those parameters on the calculated static pressure rating and the design fatigue life and gives recommendations for optimizing the parameters of the design itself (e.g. blend radii at transitions) and the analysis considering the required accuracy of the result, analysis time and cost.

Sign in / Sign up

Export Citation Format

Share Document