Float-Over at High Air Gap Design and Issues

Abstract

There is a long history of successful deck installation by float-over deck method: it has been in use as an effective installation method since the seventies. The concept offers the advantage of significant savings in transportation and installation cost by minimizing the installation time and offshore hook-up and eliminating the need for a heavy lift derrick barge. The method was developed for, and has found wide applicability to deck requiring a relatively low air gap. To allow the float-over method to be extended to harsher environmental areas, several new solutions, which are applicable to platforms requiring air gaps of 20m (66ft) or more, have been developed. This paper describes the technologies used today for deck installation at high air gap and analyzes the strength, weaknesses, opportunities and threats of each of these float-over technologies by an overview of the main issues related to: - Installation concept (Ballasting vs. elevating system). - Transportation method. - Environmental conditions. The design, fabrication and operation of the different solutions will be discussed in this paper. To allow the float-over method to be safely extended to more remote exposed field location understanding the issues associated with the different designs presented in this paper will become important.