A Disconnectable Dry Tree Semisubmersible Design Exposed to Iceberg and Harsh Environment Available to Purchase

This paper presents an innovative design for a disconnectable dry tree semisubmersible floater for use in harsh environments and which could be exposed to the threat of iceberg impact. The use of dry tree Top Tensioned Risers (TTRs) in well completion has its advantage in allowing direct vertical access to production wells, which enables the use of dry-trees, drilling programs, and well work-over when required. Semisubmersible floaters offer significant execution and operational advantages over other types of floaters such as the quayside integration, and high flexibility on the payload and topsides area requirements. However, with the existing qualified tensioner technology, conventional semisubmersibles do not offer motion response suitable for dry tree applications. The free hanging solid ballast semi (FHSB Semi) is an enhanced semisubmersible design that maintains the advantages of the semisubmersibles while offering a very low motion response suitable for dry tree applications. The design and characteristics of the FHSB Semi is widely published elsewhere. In an area where floating platforms are exposed to icebergs and harsh environment, it is essential to design a system where the floater can be disconnected from the moorings and top-tensioned risers and be moved away from the iceberg's path. After the event the system should be designed to reconnect moorings and risers with minimal disruption to production and reasonable restriction on the reconnection environment. In this study, the FHSB Semi design has been further developed to enable disconnect/reconnect of the TTR and mooring systems. Detailed description of the disconnectable TTR and mooring systems is presented in this paper. A case study is also presented to illustrate the performance and the disconnection/reconnection of a FHSB Semi located offshore Newfoundland in a harsh environment area subject to icebergs.