The Underwater Production System (UPS) is a subsea hydrocarbon productionsystem developed jointly by Statoil and Mobil Exploration Norway, through aproject team based in Trondheim, Norway. This paper presents a description ofthe system and the key development activities which led to the project goal ofa fully developed system design.
The UPS was conceived by Statoil in 1984. After a year of in-house development,Statoil approached Mobil with a proposal to pursue the developmentjointly. In September 1986 the two companies staffed and funded the program, which was completed in early 1989.
The primary interest of the sponsoring companies was the development of thecapability to safely produce hydrocarbons from fields beyond diver depth, using"wet" technology. In the wake of the recent oil price collapse, addedemphasis was placed on the economic aspects of such a capability. The agreedobjective of the UPS Project was to provide a fully developed design of asystem ready for application in the early 1990's. The feasibility of the systemwas to be verified through system engineering and fabrication/testing ofselected hardware.
The design basis for the UPS was drawn from North Sea experience. Conservativeconditions were selected while avoiding extremes which would have excessivelydriven the design. The principal requirements were as follows:
Northern North Sea environment
Distance to field control center: 20 km
Depth: 400 m to guideline limit
Design life: 20 years
Six well slots, dedicated to either template or satellite trees
90,000 bbl fluid/day peak production
Maximum wellhead pressure: 5,000 psi
Wellhead temperature: 100° C
C2O and H2S service
Multifunctional inhibitor delivery to each tree.
The main aspects of the design philosophy are summarized below (please referto Figure 1 for an overview):
Wet, modular design
Diverless installation and maintenance
Overtrawlable subsea station, with dropped object protection
Through flowline (TFL) well maintenance, with back-up wireline access
Applicable ROV for inspection and Assistance
Dedicated remotely operated tool (ROT) for component change-out
Common guideline running tool for module change-out
Piggable production flowlines
Individual well test capacity
Redundant electrohydraulic multiplex control system
Retrievable control pods, cables and Piping
Vertical connections for modules, horizontal for flowlines.
Existing technology was to be used where possible. New technology was to belimited only to areas where it was deemed essential to achieve the projectobjective.
The subsea station flow diagram was established to meet the design philosophyand satisfy the design requirements of the system. All active componentssubject to failure were modularized to permit their retrieval. The flow diagramindicates the following equipment (Figure 1).