BP currently operates approximately 200 subsea wells worldwide Wells are located in many regions, and operate in diverse environments. Wells are located in water depths from 25 metres to below 1600 metres, and from warm-water locations such as Indonesia to cold-water environments, such as the North-Sea.
Within these subsea systems, one of the most common failure modes noted is attributed to electrical Systems.
The purpose of this paper is to describe some of the failures that BP has experienced with subsea electrical connection systems. The paper will concentrate on two distinctly different systems, namely BP Indonesia and West of Shetland
Indonesia is an example of a geographically remote system where equipment operates in a shallow (diver depth) warm water environment, whilst West of Shetland is an example of a deepwater (Remote intervention) and hairshweather environment
The paper aims to give an overview of the problems experienced, as well as an insight into some of the factors associated with managing failures in both of these environments and regions. It aims to show how common lessons can be learned from these two systems that may help to prevent these failures from occurring in future developments.
It should be noted that the intent of is not to identify specific failures attributed to connector manufacturers designs, however it is aims to highlight critical elements and interfaces that may need specific focus and attention during the design and operation phases of a subsea system
Both controls suppliers and connector manufacturer have been involved with the failures identified within this paper.
The failures observed in both subsea systems are not believed to be isolated events within the subsea industry, and both systems have noted common modes of failures These failures have resulted in High intervention costs and loss of production to carry out diagnostics and to complete remedial Work.
The majority of failures experienced were believed to be extrinsic or failures that were outwith of the design intent of the electrical system. This identifies that designers, as well as controls and umbilical system supplier need to become more aware of the design and operational criteria of subsea electrical systems. It also highlight that the industry needs to ensure that connector manufacturers be more involved with both system design considerations and operational requirements. In return, connector manufacturers need to be pro-active with their failure diagnostics, and sympathetic with their understanding of the operational requirements
As most of the failures were believed to be due to extrinsic mechanisms, this clearly highlights requirement for some form of best practice / common expectation guidelines to be written for electrical termination work.
The electrical system is a crital of a subsea system, and therefore due consideration needs to be placed on the design, diagnostic and fault finding capability of the system architecture and design
The environmental effects and location of the subsea system may also play a factor in the design of the system and the connector. These need to be carefully reviewed during the project phase, and needs to be considered by connector and controls/umbilical system suppliers. Transportation, storage and testing conditions prior to emersion also need careful consideration.