The Jackup Monopile: A Production Drilling Platform

ABSTRACT The paper describes the main conceptual and design aspects of a Jack-Up Monopile Platform concept intended for drilling and production in North Sea and which combines technology from Gravity Base Platforms and Jack-Up Rigs. The platformcomprises3 main elements:An integrated deck, completely equipped and tested on shore prior to installationA single supporting leg with its associated jacking systemA gravity base that ensures the stability on site and during towing and can provide for extra storage The derrick and drill floor operate over the centre of the leg structure, and risers are installed through its centre, thus providing protection against damage from supply boats. The Jack-Up Monopile Platform has been designed for 150 meters water depth in North Sea environment. It provides for a total deck payload of 10 600 tonnes which includes:Accommodation facilities for 160 personsDrilling equipments for 24 wells at 7 000 metres depthProduction equipments including injection equipment for processing 120 000 barrels oil per dayPower and utilities necessary to maintain the efficient platform operation The design allows complete fabrication and hook up of all the platform facilities to take place at an offshore construction yard prior to installation at a field location, without the need of deep water mating sites nor the use of heavy lift vessels. The key advantage is its ability to be decommissioned easily and relocated after any eventual upgrading of its facilities. This improves the cost effective aspect of such a design and makes it specially fitted to marginal field development. The Jack-Up Monopile Platform has been Specifically developed to meet North Sea environmental conditions and regulations and is self erected, self installed, with risers efficiently protected and can be easily decommissioned for use on other fields, thus providing operators with a cost effective development solution. INTRODUCTION For big oil fields, a conventional development scheme consists in installing a jacket or a concrete platform with several separate modules (drilling, production, injection, accommodation, etc...) to be towed out and installed on the site, thus requiring heavy lift vessels and high hook up costs. Such a development can take several years before first oil and so corresponds to a very high investment cost before production. For satellite or marginal fields, some other possibilities exist such as subsea developments or use of floating production facilities. They imply subsea wellheads and completions for which technology is sophisticated. For many years now, designers have proposed mobile concepts that combine both drilling and production options. One of this transposition concerns the jack-up concept which technology is cost-effective and well-proven now. With regards to semis which motions can be important and which are weight sensitive, jack-ups allow for early production using conventional wellheads at the platform level. Unfortunately, conventional jack-ups cannot operate in water depth greater than 100/110 metres in North Sea.