The paper presents a design review of major diverless subsea development schemes covering concept, prototype and live installations. The paper describes the main features and maintenance intervention philosophies of these developments and highlights those design principles developed in the last decade which are likely to be in use during the early 1990's.

Several distinct development themes are identified in the paper including: the use of established drilling technology as a means of retrieving modules; the use of special purpose remote vehicles to retrieve modules or single components; and the use of commercially available ROV's to replace individual components. Each of these main intervention methods can be applied to diverless subsea developments.


This paper which is based on work undertaken by Fuel Subsea Engineering Limited for BP Exploration reviews the design of diverless subsea systems over the last decade to provide a historical context for those engineering issues which will shape current and future development plans.

The scope of the review was not unlimited and therefore criteria had to be established for identifying systems to be considered; these are

  • Systems in production

  • Systems under development

  • Conceptual systems

  • Systems on a global basis

The review identified differences and similarities between the diverless subsea system designs by assessing each system in terms of the overall system design and in terms of major subsystems, via:
  • Overall system philosophy and configuration

  • Flowlines

  • Manifold/Template

  • Xmas tree

  • Control system

  • Maintenance

  • Intervention vehicles

Eighteen systems were investigated in some detail and a further five systems considered briefly. The systems considered are shown by geographical location in Table 1.

The review of each system was based on the most recent data available in the public domain during the research period. Direct contact with relevant operators, authors or design contractors was not made and therefore it was not possible to verify the published data.

Data sources reviewed were technical proceedings from various conferences including Offshore Technology Conference; Offshore Europe Conference Underwater Technology Conference; offshore Northern Seas Conference; and Deep Offshore Technology Conference and other technical publications, including magazines. The number of individual references was extensive, with over 60 papers being reviewed in the course of the work. For this reason individual references are not given in this paper.


Reservoir and economic factors are the primary aspects in determining whether a particular hydrocarbon field has the potential for development by subsea means. Once a subsea system is to be considered, the way in which the system is to be installed, operated and maintained is the most significant technical issue. However, there have been almost as many technical solutions proposed as projects undertaken. This lack of consistency is due to the evolving nature of the industry, which has yet to 'mature'.

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