First Jack-Up Production Platform In North Sea

ABSTRACT This paper describes the platform design engineering aspects of Amoco's jack-up gas production platform which was installed in August, 1972. It is the first jack-up production platform installed in the North Sea. The main advantage of using the jack-up platform as compared with the conventional template-type platform is that all production, storage, and living facilities can be installed, tested, and checked out in the fabrication yard prior to leaving for installation. As a result, considerable expensive offshore work is avoided, and more important, much less time is required to commission the production facilities and begin operation. INTRODUCTION The Oil Industry is constantly searching for new methods and systems to reduce the high cost of offshore installations. Particular interest is being shown in producing facilities required to be located offshore. These installations can vary in size from a single separator to a bulky, highly instrumented gas dehydration complex. The first step toward economy was the "skid mounted" unit which combined a principal unit with pumps, meters and instrumentation installed and possibly tested on a set of skids designed for lifting into place on the offshore platform. Later the deck sections were sectionalized. The equipment was installed integrally with the deck section pieces and then finally assembled and tested offshore. Still later the idea of "production packages" (more commonly referred to now as modules) came into use. For the larger facilities and deep water locations this method appears to be the most popular at the present time. To date, this arrangement appears to be planned for all deep water North Sea installations. For this type operation the equipment is installed in a series of structural steel boxes. The boxes are fabricated in the yard in the exact position they will occupy in their final location offshore to insure a final, correct inter-connection. The entire system can then be tested as a unit in the yard. Once installed offshore only a minimum amount of final testing is required. One type of permanent installation that has seen limited use is the "jack-up" barge. Some use has been made in the Gulf of Mexico, but principally for storage. One such installation for large separator units is known by the writers to be in use in the Middle East. Amoco, having used the three previous mentioned methods in the British North Sea, investigated the use of a jack-up barge, in an effort to further reduce offshore connection work and testing. The results of the investigation showed this method feasible and economical up to approximately 100 ft. water depth. The decision was made to use the "jack-up" barge concept on a gas dehydration facility to be installed in a 75 ft. water depth location in the Leman Field, British North Sea.