Kerr-McGee's and Devon Energy's Red Hawk spar was installed at GB 876 in approximately 5,300 ft water depth (WD) in April 2004. This is the first use of Technip's third generation spar (cell spar) and is one of the first permanent deepwater floaters in full production to use a passive polyester Taut Leg Mooring (TLM) in the Gulf of Mexico (GOM). This paper describes the planning and installation of the Red Hawk cell spar and the polyester mooring system using a Construction and Anchor Handling Tug (CAHT).
When Kerr-McGee (KMG) and their partner Devon Energy (DVN) awarded the contract to Technip Offshore, Inc. (TOI) for the Red Hawk cell spar in December 2002, there were several major considerations in the selection process. These included aggressive pricing and delivery schedules, a robust design with a topsides payload that met field expansion plans, local involvement in the engineering and fabrication, and the provision of an excellent candidate for future low cost field developments. The details of project overview and project management are discussed in a separate paper (Ref [5]). The use of polyester rope in the TLM, one of the first permanent mooring applications of this technology to be installed in the GOM, is a significant step in the permanent mooring of ultradeep floating production facilities.
The 560-ft long cell spar uses seven (7) individual 20-ft diameter tubes configured with six (6) tubes surrounding a central core tube resulting in an overall hull diameter of approximately 64 feet (Figure 1). The design also allows each tube or cell to be produced using standard pressure vessel manufacturing techniques, simplifying overall hull assembly (Figure 3), and minimizing hull fabrication schedule. A purpose built large diameter pile rack (LDR) was installed at the Gulf Marine Fabricators yard in Ingleside and the same equipment was used in the rolling and joining of the cell sections and for fabrication of the Suction Embedment Anchors (SEAs) used in the mooring system.
In order to simplify the installation process and to minimize costs, a decision was made early on to use Heerema's Dynamically Positioned SSCV Balder to perform a single deck lift of the 3,600-ton topsides. The remainder of the installation processes (e.g. support during hull upending, preset mooring deployment and platform attachment operations) were completed by using the Construction and Anchor Handling Tug (CAHT) Dove with support from other vessels. Red Hawk is the first spar that has been upended and attached to mooring lines without the involvement of derrick barges or construction vessels. This also is the first time that the offshore branch of Technip Offshore, Inc. in the United States has taken on an offshore contract with full EPCI responsibility, inclusive of the delivery and installation of the mooring system.
Another key design decision was to minimize the amount of platform mooring equipment to be installed on the spar. All other spars installed to date have chain jacking equipment located at every mooring leg.
