Snorre Subsea Production Systems: Land Test And Installation Experience
Authors: Overgaard Ingar , Boles B.D. , Jensen oyvin 
Published: October 2008

Installation of equipment has been completed in preparation for production start of the first subsea well in the Snorre Field Development Project. The ten well Subsea Production System (SPS) is located in 335 m of water, 6 km away from the Tension Leg Platform (TLP). A comprehensive job was performed by several Engineering, Procurement, and Construction (EPC) contractors, both in meeting contractual milestones and providing adequate subsystems which compose the Snorre SPS.

The system has earlier been described in OTC papers 6202 (Ref. 1) and 6625 (Ref. 2). This follow-up paper expands the discussion to cover a thorough land test of the system with elements of subsea testing for critical components, a description of the installation of the template and manifold, and the flowlines and umbilicals, commissioning activities on board the TLP, the drilling and completion approach including installation of the first subsea tree, and the use of a relatively sophisticated Remotely Operated Maintenance Vehicle.

BRIEF SYSTEM DESCRIPTION

The Snorre Subsea Production System is shown in Fig. 1, which identifies the various sub-systems. It can accommodate 10 wells at one time, and with a 10+ 10 well arrangement, the plan is to drill approximately 20 wells from it without reuse of slots. The template and manifold is 48 metres long, 32 metres wide, and (including the 3 metres skirts) 19 metres tall.

Installation weight was 2,400 tonnes. The design oil production capacity is 9,300 cubic metres per day (approximately 58,500 bopd). Special features of the system include:guidelineless handling of equipment,TFL (through flowline) capabilitiesuniversal manifold, i.e. each well slot can be tied into either a low or high pressure production header or a water injection header,designed for simultaneous drilling and production as well as maintenance, anddiverless maintenance.

SYSTEM LAND TEST

A comprehensive program of testing equipment delivered by the EPC contractors began immediately following the delivery of the template and manifold to Saga in March 1991. At this point, the control system was integrated within the manifold, one of the subsea trees and associated running/handling tools were available, the flowline and umbilical pull-in and connection equipment was delivered, and short lengths of the flowlines were available for interface testing. The Remotely Operated Maintenance Vehicle (ROMV) would come to the test site some months later for interface and operational checks.

The land test program was established to:check interfaces between equipmentverify functionality of the control system,confirm TFL tool and pig passage through the manifold,perform operator training, andverify commissioning and operational procedures,

The test program was established to verify those interfaces which had not been previously tested and to confirm dimensional aspects of equipment from different contractors. The flowline and umbilical end connections were test fit and interchanged before being returned to the contractors for fit to the actual flowlines and umbilicals. The subsea tree was test fit in all wellbays, both inner and outer slots. During this process, the control system was checked wellbay by wellbay for proper function.