Ormen Lange Subsea Production System

Abstract

This article, written by Technology Editor Dennis Denney, contains highlights of paper OTC 18965, "Ormen Lange Subsea Production System," by Thomas Bernt, Hydro, and Endre Smedsrud, FMC Technologies, prepared for the 2007 Offshore Technology Conference, Houston, 30 April-3 May. The Ormen Lange field, in the Norwegian Sea, approximately 100 km off Norway, is within the prehistoric Storegga slide area with water depths reaching 850 m in the main production area. The gas will be produced from up to 24 subsea wells. The well fluid will be transported to the Nyhamna plant through two 30-in. multiphase lines. After processing, the dry export gas will be transported from the onshore plant through a new 42-in. pipeline by way of the Sleipner riser platform and further through a new 44-in. pipeline to the gas-receiving terminal in Easington, England. Introduction Fig. 1 shows the development concept selected for Ormen Lange, which comprises a subsea tieback to an onshore processing plant at Nyhamna. Conceptual engineering of the subsea production system was initiated in 2002. The main contracts for subsea-equipment supply, umbilical fabrication, and template installation were awarded between the autumn of 2003 and the summer of 2004. The main part of fabrication and testing took place during 2004–05, with the subsea templates installed offshore in late summer 2005. Umbilical A and the remaining subsea equipment were installed during the summer of 2006, and the first subsea tree was installed on Template A in December 2006. Completion of the first subsea well on Template A was scheduled for spring 2007, and subsea production startup was scheduled for autumn of 2007. Subsea-System Configuration With the large geographical extent of the Ormen Lange reservoir and the risk of reservoir segmentation, the subsea-system design has a high degree of flexibility, with four planned template locations. Therefore, a phased-development scheme was chosen. The phasing and location of the subsea wells will be timed to maintain plateau production as the field depletes. Initial Development. The initial sub-sea development consists of two eight-slot production templates (Templates A and B), approximately 4 km apart in the main production area. Each tem-plate is tied back into the two 30-in. multiphase pipelines to shore. As Fig. 2 shows, these lines are interconnected through a pipeline-end-termination (PLET) system. Two main control umbilicals link the onshore plant to the subsea production system; one is connected to Template A and the other to Template B. A cross-over-control umbilical interconnects the two production templates, providing redundant hydraulic supply to all the subsea wells. To prevent hydrate formation, all wells are injected continuously with monoethylene glycol (MEG) through two 6-in. pipelines from the onshore plant. One line is connected to Template A and the other to Template B. A 6-in. crossover-MEG line interconnects the two production templates for added flexibility.