Development of the Ultimate Ultra Harsh Environment Jack-up Drilling Rigs

Abstract

Drilling with jack-ups in harsh environments has moved into deeper and deeper water during the last 10 years. Previously 90 m was considered the maximum whereas up to 150 m water depth is now feasible. In addition several new features are now available on harsh environment jack-ups which increase the drilling efficiency by up to 25% compared with the more conventional jack-up types. This paper describes the process of creating the next generation deepwater jack-up drilling rig, and the results and operational experience with the Maersk "I" class rigs - the Maersk Innovator and the Maersk Inspirer. The Maersk Innovator has been in operation for approximately 18 months and the Maersk Inspirer is in transit to the North Sea. The Maersk Inspirer is contracted to start operating in February 2005. Design Phase Maersk Contractors operates a number of ultra harsh environment rigs in the North Sea (NS). Based on experience with these rigs the functional requirements to the next generation of ultra harsh environment jack-up rigs were developed. The overall focus was to further improve the safety level onboard from previous rigs and provide more value for money to the clients. This can be obtained by reducing the need for costly modifications for specific operations and improvement of the overall drilling efficiency in the design. A large number of NS operators were consulted in order to obtain their view of the ideal rig in the future. More than 650 suggestions were formally received from the rig crews on the existing fleet, of which more than 450 were incorporated in the final design. In addition a number of presentations/discussions were conducted onboard the rigs in order to get "real life" feedback and comments. A 1:1 mock-up of the drill floor with simulated work situations was used to gather valuable input to the layout. The modifications, which have been required on Maersk Gallant (an MSC-CJ 62 design) to operate with extended reach/skid-off (ref. 1) and at increased water depth of 125 m at Statoil's Huldra Field, were evaluated. Use of the rigs in subsea and production mode was also considered. The MSC-CJ70 was chosen as the basic design and the concept was developed together with MSC. This included an XY cantilever system which provides opportunities to increase efficiency and introduce improvements on the drill floor (ref. 2). The Rigs General/Structural performance. The rigs have a leg length of 205 m with a permanent skirted spudcan which gives a water depth capability in the NS of up to 150 m (Fig. 1). The variable deck load at 150 m water depth is 4000 mT. At lower water depth the deck load is significantly higher, up to 10,000 mT depending on the seabed conditions (Fig. 2). At the Shell Goldeneye location in 120 m water depth the variable deck load was 9,000 mT, which was utilised to a great extent. The 120-man accommodation is placed in a V-Shape around the forward leg with a sleeping side and a "noisy side" with offices, mess room, recreation rooms, etc., This together with the location of all ventilation ducts, etc. in three separate houses next to the legs gives a very large useable deck area of 2,500 m2 compared to 1500 m2 on rigs with similar hull sizes (Fig. 3a). A forklift is used on the main deck to reduce the number of crane lifts and thereby improve safety. Below deck the layout is optimised with regard to safety and working environment with two separate engine rooms, pipe trunk and straight escape routes enabling protected escape routes from anywhere on the rig (Fig. 3b).