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ABSTRACT The increase in deepwater exploration activity has generated increased use of the Floating Production/Storage Offloading Systems (FPSO's). Converting existing tankers is, in many cases, more economically feasible and faster than building new FPSO's for the same purpose. For conversion of tankers to FPSO's, inspection and subsequent fitness for purpose assessment are crucially important. The objective of this paper is to present the principles and strategies of in-service inspection programs for FPSO's. The paper summarizes the technical basis for three levels of inspection strategies:probability-based inspection method, risk-based inspection method, and 'optimum' inspection method. INTRODUCTION FPSO's have many attractive features including relative low cost, large working area, large water surface area, and good stability and floatability. FPSO's in many cases, are converted from existing tankers. It is therefore important to have a rational and reliable inspection method to provide information and knowledge concerning the proposed, present, and future integrity of FPSO's. FPSO inspections should be focused on:determination of condition of structural elements and structural system, disclosure of defects (design, construction, operation, and maintenance), assurance of conformance with plans, specifications, guidelines, rules, and quality requirements, disclosure of damage, and development of information to improve design, construction, operation, and maintenance procedures. FPSO inspections have several levels of intensity:general (global conditions), specific (basic aspects of defects and damage), and detailed (precise descriptions of flaws and other items of operation and maintenance concern). FPSO inspections should be life-cycle oriented and include quality assurance and control measures in:design, construction, operation, maintenance, and accidents / casualties. FPSO inspections should be full-scope and include quality assurance and control measures of the structure, equipment, facilities, and personnel. Research in inspection has been conducted in regulatory organizations, universities, and other leading organizations. [1, 2, 3, 4]. Some important guidelines have been developed for offshore inspection practices. The objective of this paper is to present the principles of development of in-service inspection strategies for FPSO's. PROBABILITY BASED INSPECTION A number of limitations of in-service inspections have been identified [3, 4, 5], especially the significant uncertainties in design, fabrication and damage detection, as well as the adequacy of examining only a limited amount of the structural elements. The usefulness of probabilistic models to deal with uncertainties, as well as Bayesian models has been recognized. The probabilitybased inspection method is thus developed to include Bayesian analysis, and probability-based inspection planning. Bayesian Analysis The bulk of research on Bayesian analysis in engineering application was first conducted in early 1970's. This approach, defined as the probability of detection (POD) updating method, was widely applied in aeronautical engineering systems, such as airframes, gas turbine engines [6]. In the late 1980s, an alternative Bayesian approach was developed as event updating using First Order Reliability Method (FOSM) in the offshore industry[7]
Abstract Hurricane Roxanne is marked in the history of Bay of Campeche as one of the most severe storms that hit the zone during this century, and therefore questioned the validity of the design criteria applied at that time. As a consequence, a newborn own risk based criteria was developed for design and assessment of submarine pipelines and platforms in Bay of Campeche. Petrรณleos Mexicanos (PEMEX) and Instituto Mexicano del Petrรณleo (IMP) developed and issued such criteria in 1998, named Offshore Pipeline Transitory Criteria. The Transitory Criteria is based on risk assessment and management approach. It is intended in this paper to show the result obtained so far of that development. Safety and serviceability categories for pipelines are defined. Safety factors for design and reassessment of wall thickness by internal pressure are determined based on risk approach. Practice recommendations for the design and requalification for hydrodynamic stability of submarine pipelines and risers are established. Safety factors for hydrodynamic stability are obtained following this criteria, and oceanographic characterization of the Bay of Campeche are presented in easy-reading charts for design and requalification. Introduction Hurricane Roxanne, which it is marked in the history of Bay of Campeche (BOC), Gulf of Mexico, as one of the most severe storm ever that hit the zone during this century, questioned one more time that the design criteria applied at that time showed some deficiency. As a consequence, an own risk based criteria was developed for design and assessment of submarine pipelines and platforms in BOC. PEMEX and IMP developed and issued such criteria in 1998. Thus, PEMEX elected to develop pipeline requalification guidelines specifically for BOC conditions. IMP engineering was called on by PEMEX to direct and lead these developments. The new criteria and guidelines were to be based on the work that Prof. Robert G. Bea from the University of California in Berkeley developed specifically for BOC conditions and the best of the technology incorporated into the existing guidelines (Bea, 1997). A two year intensive work was required before the first edition of the criteria and guidelines, named Transitory Criteria (TC). This paper addresses categorization of pipeline for serviceability and safety, wall thickness safety factors due to internal pressure, oceanographic characterization of BOC and hydrodynamic stability safety factors that must be used in a submarine pipeline for design or requalification in the BOC. Risk Study and Failure Probability The risk study was conducted by taking into account the economical aspect, historical behaviour, and recommendations of international codes in order to determine the failure probability of pipelines corresponding to design and requalification. Cost-Benefit Analysis. The economic analysis for obtaining the failure probability took into consideration the initial cost of design and construction, and the cost of failure (lost of production, facilities damages, and lost of human lives). The optimum failure probability (Pfo) is the failure probability that produces the lowest expected total cost. This probability (Pfo) defines the acceptable, and desirable probability of failure for the design of new pipelines. Cost-Benefit Analysis. The economic analysis for obtaining the failure probability took into consideration the initial cost of design and construction, and the cost of failure (lost of production, facilities damages, and lost of human lives). The optimum failure probability (Pfo) is the failure probability that produces the lowest expected total cost. This probability (Pfo) defines the acceptable, and desirable probability of failure for the design of new pipelines.
- North America > Mexico > Gulf of Mexico > Bay of Campeche (1.00)
- North America > Mexico > Campeche (1.00)
- Government > Regional Government > North America Government > Mexico Government (1.00)
- Energy > Oil & Gas > Midstream (1.00)
- North America > Mexico > Gulf of Mexico > Bay of Campeche (0.89)
- Europe > United Kingdom > North Sea > Southern North Sea > Southern Gas Basin > Silver Pit Basin > Block 49/30c > Davy Fields > Brown Field > Rotliegend Formation (0.89)
Reliability-Based Design Criteria for Floating Drilling & Production Structures in the Bay of Campeche
Bea, R.G. (University of California at Berkeley ) | Xu, T. (University of California at Berkeley ) | Ramos, R. (Instituto Mexicano de Petroleo ) | Valle, O. (Instituto Mexicano de Petroleo ) | Valdes, V. (Petroleos Mexicano )
Abstract This paper summarizes Risk Assessment & Management (RAM) based criteria that have been developed by Petroleos Mexicanos (PEMEX) and Instituto Mexicano de Petroleo (IMP) for design of floating drilling and production structures located in the Bay of Campeche, Mexico. The RAM approach addresses the primary structural components that comprise floating drilling and production systems, reliabilities of the components and systems based on economic and standards-of-practice methods, operating and environmental conditions, life-cycle quality assurance and control programs including inspections, maintenance, and repairs, proposed analytical models used to determine structure loadings and capacities (Working Stress Design format, Load and Resistance Factor Design format, and Limit State Design format), variabilities and uncertainties in the demand and capacity parameters, and proposed measurement, observation, and monitoring programs. These criteria have been founded on guidelines developed by the American Petroleum Institute for floating drilling and production structures. The criteria summarized in this paper address hurricane characteristics in the Bay of Campeche, strength characteristics of the structures, damaged and defective conditions that can develop in the structures due to accidents, and the unique capacity characteristics of the elements that comprise floating structures including the surface structure elements and mooring systems. The criteria are 'information sensitive' so that as additional information is gathered on the demand (loading) and capacity characteristics, then the criteria can be changed in response to the new information. The criteria are 'quality' sensitive so that as improved quality assurance and control and advanced marine structural integrity programs are utilized, the effects of these programs are reflected in the criteria. Introduction These hurricane design criteria have two primary parts:Definition of the procedures and parameters to be used in design to characterize the hurricane conditions and forces, and Definition of the procedures and parameters to be used in design to determine the sizing of the primary structural components in deep water floating systems. The definition of design environmental conditions was based on the studies of hurricane conditions in the Bay of Campeche performed by Oceanweather. The definition of rocedures to be used to determine the forces acting on floating structure components were founded on the American Petroleum Institute (API) guidelines for design, analysis, and maintenance of moorings for floating drilling and production systems, design of tension leg platforms, design of fixed offshore platforms, and design and analysis of risers for floating drilling units. The definition of the procedures to be used to determine the sizing of the primary structural components in floating systems are founded on the API guidelines for design, analysis, and maintenance of moorings for floating drilling and production systems, the guidelines for planning, designing, and constructing tension leg and fixed offshore platforms, and the API guidelines for design of cylindrical shells and flat plate structures.
- North America > Mexico > Gulf of Mexico > Bay of Campeche (1.00)
- North America > Mexico > Campeche (1.00)
- Energy > Oil & Gas > Upstream (1.00)
- Government > Regional Government > North America Government > Mexico Government (0.88)
Abstract Experience with Mobile Offshore Drilling Units (MODUs) in recent hurricanes in the Gulf of Mexico (GOM) has indicated the need to reassess where and how these units are sited. During hurricane Andrew (1992), several of these units moved significant distances (up to ISO km) from their original locations. In several instances there were collisions with platforms and pipelines. Also, in the case of hurricanes weather conditions can deteriorate rapidly, and timely decisions are critical to allow proper securing and evacuation of MODU's. This is particularly crucial in areas with high storm intensity and low predictability. The primary objective of this research was to develop an analytical model to evaluate MODUs' movements in response to the combined load effects of hurricane winds, waves and currents, then use a Monte-Carlo simulation process to evaluate the probability of collisions between the MODU and surrounding large facilities. The computer simulation program was developed, and has been used to investigate alternative siting strategies. The strategies investigated include location of the MODU relative to nearby facilities, capacities of the mooring systems, and incorporation of intentional 'weak links' in the mooring system to cause either the mooring to the anchor connections to break, or the anchors to drag. The results of the parametric studies of alternative siting and mooring strategies are summarized. The second objective of this research was to use probabilistic risk analysis techniques to develop a computer model to help evaluate operation and evacuation systems for MODUs. Results from the evacuation simulation model are intended to assist in developing decision criteria for securing and evacuating MODUs. Approach Fig. I summarizes the approach used to develop, verify and implement the simulation models. Based on fundamentals of statistics, hurricane forecasting and modeling, fluid dynamics, mooring strength analysis, and Monte Carlo techniques, the first step was to develop a basic simulation model, to evaluate the movement of MODUs in hurricanes. The program was then used to develop siting strategies for Mobile Offshore Drilling Units. The simulation model incorporates models of hurricane winds, waves, currents, and tracks; storm wind, wave and current forces; mooring capacity characteristics, and finally, a model of movement characteristics that takes into account free floating, intermittent grounding ('skipping'), collision 'holding', and anchor dragging characteristics of MODUs. The program allows the user to specify hurricane characteristics in a probabilistic or deterministic manner. A Monte-Carlo simulation model is utilized to perform probabilistic calculations. The model includes a Markov model to describe the probabilities associated with changes in the tracks of the hurricanes. The model incorporates variable hurricane parameters and their correlation, the storm spatial geometry, and shallow water shoaling effects. The developed program allows one to define the locations and sizes of 'critical facilities' near the MODU location, and then evaluate the probabilities of collisions between the MODU and the critical facilities. The organization and theoretical basis for the program will be detailed later in this paper. Based on the project management and network simulation techniques, a computer simulation model was developed to help evaluate operation and evacuation systems for MODUs in hurricanes. Probabilistic risk analysis and Monte Carlo techniques are used in the model to address the large uncertainties in hurricane forecasts and in the evacuation process.
Risk Assessment & Management Based Criteria for Design and Requalification of Pipelines and Risers in the Bay of Campeche
Bea, R.G. (University of California at Berkeley ) | Ramos, R. (Instituto Mexicano del Petroleo ) | Hernandez, T. (Instituto Mexicano del Petroleo ) | Valle, O. (Instituto Mexicano del Petroleo ) | Valdes, V. (Petroleos Mexicano ) | Maya, R. (Petroleos Mexicano )
Abstract Risk Assessment and Management (RAM) based criteria for the design and requalification of pipelines and risers in the Bay of Campeche have been developed and implemented by PEMEX and IMP. The criteria address pipeline pressure integrity and corrosion, hydrodynamic stability, and capacity to withstand movements of the sea floor soils (the soft sea floor soils in the Bay of Campeche develop significant motions during hurricanes). The pipelines are assessed for three Safety and Serviceability Classifications. The SSC are based on risk acceptance criteria derived from considerations of economics, historic performance of pipelines, and current standards-of practice. Desirable and acceptable reliabilities of the pipelines for the three conditions cited are defined. Reliability formulations of pipeline 'demands' and 'capacities' are developed for loss of containment integrity due to corrosion, and hydrodynamic instability. Design for corrosion is linked to Inspection, Maintenance, and Repair (IMR) programs that will be implemented to manage corrosion. Uncertainties and biases associated with the analytical procedures are evaluated. Given the risk based characterizations, the reliability formulations, and the assessments of uncertainties and biases, design and requalification criteria are defined. Introduction At the present time, there are more than 500 km of pipelines located in the Bay of Campeche. These pipelines transport in excess of 2 million barrels of oil and 1.5 billion cubic feet of gas per day. The majority of the pipelines are located in water depths between 30 m and 50 m. Most of these pipelines were installed in the 1980's and 1990's, with some pipelines installed in the late 1970's. In October 1995, hurricane Roxanne formed in the western Caribbean Sea, crossed the Yucatan Peninsula, and entered the Bay of Campeche. Due to a southward moving front, the hurricane did not follow the normal northerly path of most hurricanes. It was forced back into the Bay of Campeche and the eastern coast of Mexico where it did considerable damage. Roxanne was the most severe hurricane to affect the Bay of Campeche during this century. It generated environmental conditions which approximated those of 100-year return period hurricanes. The majority of damage was confined to pipelines. Pipeline damage consisted of broken and leaking connections (above and under water), and damaged weight coatings. Given the results from the pipeline inspections and fitness for purpose studies, PEMEX and IMP initiated development of Risk Assessment and Management (RAM) based criteria for design and requalification of the pipelines in the Bay of Campeche. The RAM based criteria was to take advantage of the results from the oceanographic, pipeline design and inspections. and fitness for purpose studies, recent results from studI.es conducted by DNV, AGA, ISO, BSI, and API to develop advanced criteria for design of new pipelines and assessment of existing pipelines. Probability based reliability methods were used to evaluate the full scope (environmental and operating hazards), life-cycle (design, construction, operations, maintenance, decommissioning) risk characteristics associated with the Bay of Campeche pipelines (Risk Assessment). PEMEX and IMP utilized advanced risk management and decision analysis methods to define how the criteria should be defined to develop acceptable risks (Management).
- North America > Mexico > Gulf of Mexico > Bay of Campeche (1.00)
- North America > Mexico > Campeche (1.00)
- Government > Regional Government > North America Government > Mexico Government (1.00)
- Energy > Oil & Gas > Upstream (1.00)
- Energy > Oil & Gas > Midstream (1.00)
- North America > United States > Kansas > State Field (0.93)
- North America > United States > Texas > Permian Basin > Central Basin > Brown Field (0.89)
- North America > Mexico > Gulf of Mexico > Bay of Campeche (0.89)
- Well Completion > Well Integrity > Subsurface corrosion (tubing, casing, completion equipment, conductor) (1.00)
- Production and Well Operations > Production Chemistry, Metallurgy and Biology > Corrosion inhibition and management (including H2S and CO2) (1.00)
- Management > Risk Management and Decision-Making > Risk, uncertainty, and risk assessment (1.00)
- (4 more...)
ABSTRACT Experience with Mobile Offshore Drilling Units (MODUs) in recent hurricanes in the Gulf of Mexico (GOM) has indicated the need to reassess where and how these units are sited. During hurricane Andrew (1992) several of these Units moved significant distances from their locations. In several instances there were collisions with platforms and pipelines. A computer based analytical simulation model (MODUSIM) has been developed to enable prediction of movements of MODUs in GOM hurricanes. This model incorporates models of hurricane winds. waves. currents, and tracks; storm wind, wave and current forces; a characterization of mooring capacity characteristics, and finally, a model of movement characteristics that takes account free floating, intermittently grounding ("skipping"), collision "holding", and anchor dragging characteristics. MODUSIM allows the user to specify hurricane characteristics in a probabilistic or deterministic manner. A Monte-Carlo simulation model is utilized to perform the calculations in the probabilistic regime. The model includes a Markov model to describe the probabilities associated with changes in the tracks of the hurricanes. The model incorporates variable hurricane parameters and their correlation, the storm spatial geometry, and shallow water shoaling effects. MODUSIM allows one to define the locations and sizes of "critical facilities" that are nearby the MODU location, and then evaluate the probabilities of a collision between the MODU and the critical facilities. The organization and theoretical bases for MODUSIM will be detailed. MODUSIM has been verified with the movement characteristics of three drilling units during hurricane Andrew: the Zane Barnes, Zapata Saratoga, and Treasure 75. The simulation results matched very closely the available information on the movement characteristics of these MODUs. The empirical verification, of MODUSIM will be described. MODUSIM has been used to investigate alternative sitting strategies. The strategies investigated include location of the MODU relative to nearby facilities, capacities of the mooring systems, and incorporation of intentional "weak links" in the mooring system to cause either breakage of the mooring to anchor connections or dragging of the anchors.
- North America > United States > Texas (0.47)
- North America > United States > California (0.29)
ABSTRACT This paper summarizes development of a reliability based screening procedure that can be used in platform assessments and requalifications. The maximum static force acting on a platform system is treated as a function of random variables. Its statistical properties are derived considering the uncertainties associated with environmental conditions, structure conditions, kinematics, and force calculation procedures. The statistical properties of the capacity of the platform system are characterized using a combination of parallel elements and series components. The series components are the superstructure (deck), each bay of the substructure (jacket), and the foundation. The capacity of the platform is reached when the capacity of anyone of these components is reached. Within each component there are parallel elements: deck legs, braces, joints, and piles. In order for a component to reach its capacity, all of the parallel elements have to fail. The proposed reliability analysis in this paper is based on a First Order Second Moment (FOSM) approach. A study is made of the implications of the simplified FOSM method. In the case of an eight-leg drilling and production platform located in Gulf, of Mexico, the results from FOSM reliability analysis are compared with those from First and Second Order Reliability Methods (FORM and SORM). Lognormal and Type I Extreme Value distributions were selected for characterization of the expected annual maximum wave heights. In both cases, the results are in good agreement with those from the simplified FOSM analysis. The FOSM safety indices are close approximations to those from FORM and SORM analyses. In addition to reliability indices for different failure modes, bounds for the system probability of failure are estimated. Detailed structural reliability analyses of template-type offshore platforms are prohibitive, costly and experts are needed to perform the analyses. The simplified procedure introduced in this paper is meant to enable the average structural engineer to perform reliability analyses of jacket-type offshore platforms rapidly and with sufficient accuracy.
ABSTRACT Experience has amply demonstrated that Human and Organization Factors (HOF) play important roles in determining the quality and reliability of marine structures such as ships, pipelines, and offshore platforms. This paper addresses HOF in tile contexts of approaches, assessments, and general guides that are intended to help improve the quality, safety, and reliabilityy of offshore platforms. These elements areintended to primarily address potentially critical situations involving HOF that can lead to major degradations in the quality of offshore platforms.. INTRODUCTION Experience with offshore platforms has amply demonstrated that the primary hazards to the quality, safety, and reliability of these systems are associated with the actions and inactions of the people that are involved with the design, construction, and operations of these systems. Our research on marine systems clearly shows that roughly 80 % of the manor compromises in quality can be attributed to HOF. About 80 % of these ompromises occur during operations. However, many of these operational compromises have antecedents embedded in design and construction.4 These tindings are similar to those found in a wide variety of nonmarine systems and communities.4. Experience also has amply demonstrated that traditional methods and approaches to help assure that desirable quality, safety, and reliability are developed work in the vast majority of cases. It is the rare, low probability, high consequence situations involving HOF that areslipping through the Quality Assurance and Quality Control (QA / QC) processes and associated management strategies (e.g. Total Quality Management). In themain, the contents of this paper are intended to address what is not addressed by traditional quality management activities and strategies to help assure desirable and acceptable quality in offshore platforms. The contents of this paper represent a summary of some of the key results from six years of research that have addressed the life-cycle quality, safety, and reliability aspects of a wide variety of both marine and non-marine systems. is work has involved field studies inwhich attempts have been made to apply, verify, and test the results of the research. The work includes in depth studies of information contained in major marine systems accident data bases. It continues to focus on HOF in design, construction, and operation of marine systems including platforms, pipelines, and commercial tankers. This paper does not chronicle a mature technology. There is a long way to go before this technology can be called mature. Thanks to the progress made by non marine communities such as the commercial air transportation and nuclear power plant industries, acoherent and meaningful start on the unique challenges associated with HOF in the marine community has been made. The approaches and assessment strategies outlinwl here can help those with front-line responsibilities for offshore platforms and their operations to better chieve desirable quality, safety, and reliability.. In the remainder of this paper, fiit we define quality, safety, and reliability to show how they are inter-related. This is done so that the objectives of work to improve HOF will be clear and balanced.
- Europe > United Kingdom (1.00)
- North America > United States > California (0.47)
- North America > United States > Texas > Harris County > Houston (0.28)
- Government > Regional Government > North America Government > United States Government (1.00)
- Energy > Oil & Gas > Upstream (1.00)
- Europe > Norway > North Sea > Central North Sea > South Viking Graben > Sleipner Field > Draupne Formation (0.99)
- South America > Brazil > Parnaiba Basin > Block PN-T-68 > California Field (0.89)
- Asia > Middle East > Israel > Tel Aviv District > Southern Levant Basin > National Field (0.89)
ABSTRACT The paper establishes methodologies for formulating qualitative and quantitative models to identify and evaluate the impacts of human and organizational errors (HOE) on offshore operations. Qualitative and quantitative models of simultaneous production and maintenance related to Piper Alpha disaster are used as a case study to illustrate the identification and assessment of alternatives to minimize the effects of HOE in high pressure gas system operations. Quantitative data is limited in availability and detail to assist evaluations of HOE management alternatives. However, when this data is combined with a realistic structuring of the human, organization, and system com orients of marine systems, then useful results can be developed to guide judgments to improve the reliability of these systems. INTRODUCTION Available data on the performance of marine systems during the last two decades indicates that approximately 6570 of catastrophic marine related accidents are the result of human and organizational errors (HOE) . In spite of this experience, there is no structured, general, qualitative and quantitative approach to assist engineers, operators, and regulators in the evaluation of alternatives to help minimize human and organization errors in marine systems. To be able to realize significant improvements in the reliability of marine systems, guidelines and procedures should be established to include explicit consideration of human and organizational errors as an integral part of the design, construction, and operation of offshore structures. This paper examines methodologies used to mitigate the impacts of HOE during operations of offshore structures. A case study of the Piper Alpha disaster is used to illustrate examination of the effects of HOE in simultaneous offshore maintenance and production operations of high pressure gas systems. Influence diagrams are developed to illustrate the interactions of the multiple accident events, decisions, and actions and to evaluate their contributing HOE factors. The models are used to examine HOE management alternatives reduce the likelihood of failure events. BACKGROUND Development of accident framework models is the third of five tasks in the Joint Industry Protect titled Management of Human Error in Operation of Marine Systems conducted by the Department of Naval Architecture & Offshore Engineering at the University of California at Berkeley during the past three years. The five tasks are:Identify, obtain and analyze well documented case histories and databases of tanker and offshore platform accidents whose root causes are founded in HOE. Develop a classification framework for systematically identifying and characterizing the various types of HOE. Develop general analytical frameworks based on a study of real-life case histories of major marine accidents to characterize how HOE interact to cause such accidents. Formulate quantitative analyses for the case histories based on probabilistic risk analysis (PRA) procedures using influence diagrams. Perform quantitative analyses to verify that the analyses can reproduce the results and implications from the case histories and general marine casualty statistics.
- Europe > United Kingdom (0.93)
- North America > United States > California (0.35)
- Energy > Oil & Gas > Upstream (1.00)
- Government > Regional Government > North America Government > United States Government (0.93)
The concept of fuzzy sets is applied to the reliability analysis of damaged or defective existing platforms. The damage state of the components in the structure is represented in terms of fuzzy sets which specify such condition as "severely damaged", "moderate damaged", and "slightly damaged". In formatting a reliability analysis of existing platforms, a fuzzy multi-criteria analysis is presented as one part of a comprehensive evaluation system for damage assessment. Wave loads are estimated using Stokes wave theory and Morison's formula. Probabilistic domain collapse modes are defined through a branch-bound method. Plastic collapse is evaluated accounting for damage effects. The safety margin is assessed accounting for combined load effects. The proposed method is applied to a jacket-type offshore platform. When a structure is damaged, its dominant failure modes may change because the extent, location and cause of the damage can greatly affect the structure capacity characteristics. A precise evaluation of the structure reliability is very difficult. Vague or imprecise evaluations can provide a practical and meaningful basis for damage assessment of the existing platforms. Fuzzy sets and fuzzy multi-criteria analysis can provide useful information in developing reliability evaluations of existing platforms because they can represent the subjective judgement of experts in an informative and structured manner. INTRODUCTION Currently, there are more than 6,000 major platforms sited on the world's continental shelves. Many of these platforms are experiencing extended useful economic lives due to renewed drilling activity and supplemental recovery operations. In order to minimize the risk of catastrophic failure of aged and damaged platforms, Inspection, Maintenance, and Repair (IMR) programs are important. To establish an appropriate IMR program, it is necessary to evaluate the reliability of the existing platforms. However, analyzing the reliability of a damaged platform is not an easy task due to difficulties in estimating the damaged state of the structure.
- Energy > Oil & Gas > Upstream (1.00)
- Government (0.93)