Abstract

There is an ever increasing need to extend the life of aging offshore structures beyond their original design life. Whether these structures are fixed offshore rigs or floating facilities, operators are continually looking for requalification and extension of the service life aimed at ensuring the integrity of the structure. With a continued requirement to produce oil or gas, either from the original fields or as a base for neighbouring subsea completions, many of these respective offshore installations are likely to remain operational for a period of time in the foreseeable future. The ageing offshore infrastructure presents a constant and growing challenge. Ageing is characterised by deterioration, change in operational conditions or accidental damages which, in the severe operational environment offshore, can be significant with serious consequences for installation integrity if not managed adequately and efficiently. In order to ensure technical and operational integrity of these ageing facilities, the fitness for service of these structures should be maintained.

Maximising the availability and productivity of the field, whilst operating safely and with minimal impact on the environment, is a major concern for requalification and life extension. Structural integrity management (SIM) and inspection campaigns are important inputs in the Asset Integrity Management and the maintenance of structural integrity is a significant consideration in the safety management and life extension of offshore installations. Detailed integrity assessments are needed to demonstrate that there is sufficient technical, operational and organisational integrity to continue safe operation throughout an extended service life. Information on history, characteristic data, condition data and inspection results are required to assess the current state and to predict the future state of the facility and the possible extension of service life. However unique environmental conditions, type of structures, fabrications and installation methodologies used in Middle East required attention in particular, development of hazard curves and risk mitigation of the potential regional degradation mechanisms. During the life-cycle of an offshore structure the ultimate capacity is also an important attribute that affects the life expectancy, requalification and life extension of the facility, and can significantly influence the reliability levels and operational costs.

This paper presents state of art practices in life extension of existing offshore structures and an overview of a regional hazard curves evaluation methodology and proposed regional correction factors represented risk to the integrity of a facility and the required procedures and re assessment criteria for deciding on life extension in particular the one with the importance for Middle East region. This paper also provides an overall view in the structural requirements, justifications and calibrations of the original design for the life extension to maintain the safety level by means of a maintenance and inspection programs balancing the ageing mechanisms and improving the reliability of assessment results

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