There is an increasing awareness in the oil industry, particularly with respect to subsea engineering, concerning the importance of system reliability and maintenance assessment. In new field development studies the determination of a system's production efficiency forms an important part of the decision making process regarding a field's commerciality. In line with new developments in production concepts, methods and equipment, there have also been new approaches to the analysis of future field developments, integrating more closely the system design and economic appraisals The recent slump in oil prices which has set back numerous field development studies will result in an even greater demand for in-depth assessment of production system behaviour. Attention will focus on improving both the design efficiency of a system and improving the confidence of the economic predictions
This chapter provides an overview of the role of reliability, redundancy and maintenance assessment and how it impacts upon the design efficiency of subsea developments, a section is devoted to deepwater aspects The underlying objectives are
to highlight the inter-relationship between reliability, redundancy and maintenance and their impact on system behaviour
to demonstrate the role of new performance analysis methods in assessing and optimizing production systems via practical examples
Performance analysis involves the assessment of the overall behaviour of a system considering its design, maintenance and any external parameters which affect the functionality of the system over its working life Reliability, maintainability, availability, operability and productivity analyses need to be integrated within a system performance study to assess the system's life cycle characteristics Combining performance analysis with a costing exercise permits cost-effective system design with the potential of optimizing design efficiency
Some examples are given within this chapter based upon data generated using computerized performance simulation techniques These performance simulations have been undertaken using the MAROS computer model MAROS is one of a new generation of computer packages developed to assist in system design Performance simulators, such as MAROS, function by creating realistic Me-cycle scenarios of proposed production systems.
A life-cycle scenario is a collection of events occurring during the anticipated life of the system, which conform with the system's logic and reflect its particular characteristics The events themselves can cover a wide range from the normal (expected), such as, failure and repair of equipment, routine inspection and well workover, etc, to the abnormal (undesirable), such as, loss of well or loss of pipeline, etc.
The MAROS model can cope with scheduled, unscheduled and conditional events Scheduled events occur under direct control of the user and are typical of planned maintenance activities where the system (or parts of it) are shutdown for overhaul The user specifies externally the tune(s) when such events will occur Unscheduled events are generated by random sampling from mathematical distributions Equipment failure and repair are typical unscheduled events.
