Ageing management and life extension of technical systems : concepts and methods applied to oil and gas facilities

Abstract

The oil and gas (O&G) industry is becoming increasingly interested in prolonging the operation of some facilities beyond their original design lifetime. The main challenge when extending the life of an ageing facility is to achieve a longer period of economic benefit while ensuring that safety and integrity are kept within acceptable levels. Key factors to consider are physical deterioration, operation, and maintenance of the facility, although less obvious factors may also have an important impact on safety, such as obsolescence of equipment and changes in the organisation.

The main purpose of this PhD thesis is to improve the current understanding and knowledge regarding how to manage the ageing of these O&G facilities, and what measures can be taken to extend their life. The research work is directed towards physical ageing (e.g., deterioration and maintenance) of technical systems and components installed in O&G facilities, and hence structures are not explicitly considered. However, some of the methods and approaches developed in this research can be applied to structures, and to other areas relevant for the management of ageing (e.g., obsolescence and organisational issues).

The work presented in this thesis reviews current methods and approaches used for modelling, managing, and extending the life of ageing systems. The research identifies the main challenges the O&G industry must face currently to achieve an effective management of ageing, and proposes a methodology for facilitating the implementation of ageing management and life extension assessments into existing O&G facilities. Another important issue when extending the lifetime of ageing systems is the decision making process, whose main objective is to find feasible alternatives and provide clear information to the decision maker in order to select the best one. This PhD work identifies relevant factors influencing the decision making process, and develops models and methods for assessing and selecting optimal alternatives under uncertainty.

The main contributions of this thesis are: Providing an overview of knowledge gaps and challenges for achieving an effective management of physical ageing and life extension in the O&G industry.Proposing a systematic and holistic approach based on systems engineering and information models with two main applications: (i) analysing gaps in existing O&G facilities for addressing the management of ageing; and (ii) implementing in an effective manner new procedures and methods for ageing management and life extension assessment.Identification of factors that influence the physical ageing and performance of technical systems, which are relevant for the decision making process.Development of three probabilistic models for decision making support under uncertainty:A Bayesian network for assessing the technical condition and remaining useful life of ageing repairable systems.A virtual age model for life extension assessment of ageing repairable systems.A dynamic Bayesian network for life extension assessment of ageing repairable systems. The thesis and articles present the new models and methods developed throughout the research, describe the steps needed to build and use them, and include detailed case studies with examples of application to real O&G systems. The case studies illustrate how the outputs and results obtained with these models can be used for improving the management of ageing and the assessment of life extension possibilities. Finally, the thesis summarises the work performed and results obtained, and proposes further research related to the management and life extension of ageing systems.