This paper presents an overview of the development of the Orwell gas field in the UK Southern North Sea. The production of first gas from the field in early August 1993, only 18 months after starting conceptual design and 13 months after receiving UK Government approval, has set a North Sea record in’ fast track developments, and highlighted the benefits of combining existing drilling and subsea technology.

Porches or pull tubes are typically used as conventional hang-off systems for catenary risers suspended from spars. The Hybrid Catenary Riser (HCR) is a novel hang-off alternative to suspend risers from spars where conventional hang-off systems are not available. The HCR consists of a section of flexible pipe suspended from the spar deck and running down to a location about 120 ft below the keel, where it is connected to regular Steel Catenary Riser (SCR) pipe. The flexible pipe passes through intermediate guides in the spar structure, a receptacle protruding from the spar keel, a curved guide pipe attached to the receptacle, and exits a bend stiffener attached to the curved pipe. The curved guide pipe controls the riser departure angle. During pull-in, a bend stiffener connector (BSC) will lock the bend stiffener to the curved pipe while the flexible pipe slides freely through the bend stiffener allowing the pipe to be pulled up to the spar deck. Feasibility of the HCR configuration is verified through state-of-the-art computer modeling. Installation procedures are developed to demonstrate installability. This paper presents the concept in detail and identifies its technical and economic advantages.

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