The Glider field is located in Green Canyon Block 248 in the Gulf of Mexico, approximately 165 miles south-southwest of New Orleans in around 3,400ft of water. The GC 248 lease was wholly acquired by Shell at the OCS Lease Sale 152 in 1995 for $725,000. Shell Expro holds a 75% working interest in Glider and is the project’s operator, with Newfield holding the remaining 25% equity. Total development costs have been put at about $150 million, excluding lease costs.
The discovery well was drilled in 1996, to a measured depth of approximately 16,000ft, using Diamond Offshore’s semisubmersible, the Ocean Worker. Subsequent appraisal drilling took place in 1997 and 2002. The 2002 well was subsequently cased and used as one of the project’s initial production wells.
Shell has developed Glider using two multiphase production wells tied back 7 miles to the Brutus Tension Leg Platform (TLP), located in Green Canyon Block 158 in 2,985ft of water.
The flowline system configuration consists of a single 6in buried and insulated line, which changes into a Steel Catenary Riser (SCR) at the platform end. The line terminates 10.43km from the platform at well G4 in a Pipeline End Manifold (PLEM). An additional ‘offset’ single 6in insulated flowline 1.17km long connects wells G4 and G3, again with PLEM terminations at each end.
Subsea 7 was contracted to fabricate, load-out and install the 6in rigid flowlines complete with PLEMs and SCR ‘hang-off’ from Brutus.
The company used its deep water reeled pipelay vessel, the Skandi Navica, complete with twin deep water work class ROV systems for long reach pipeline touch down monitoring and construction support for operations in 1,040m water depths.
Subsea 7 completed the installation of the fully reeled steel catenary riser with a vessel rotation of a 180° and a final transfer of the pipeline and the riser system to the hang off porch, on the TLP.
Extensive static and Finite Element (FE) analyses were undertaken to ensure flowline and SCR integrity remained within acceptable limits throughout all phases of the deepwater installation.
PIPELINE END MANIFOLD (PLEM) INSTALLATION
The installation of the PLEMs – with overall weights of up to 50kips (22.8Te) and approximate dimensions of 24ft by 10ft by 8ft – were the largest Subsea 7 had installed from the Skandi Navica to date.
To minimise the risk of PLEM rotation during installation, Subsea 7 elected to use modular buoyancy and retro-fit the termination PLEMs.
However, due to the short length of the offset flowline (3,870ft) relative to the water depth (3,250ft), this procedure was not feasible. In this case, the pipeline was initiated complete with PLEM.
Glider is the first deepwater subsea project in which Shell used a single buried and insulated flowline for tieback to the processing host. Canyon was awarded the flowline burial contract. The contract work scope included the trenching and backfill burial of the flowline to enhance the flow assurance properties of the line.
Approximately 32,000ft of line was buried, making Glider the deepest flowline burial project in the world.
Canyon Offshore deployed its new T-750 Super-Trencher from the M/V Northern Canyon to perform the trenching and burial operations, and a TRITON XLS work class ROV to conduct survey and post burial survey tasks. In addition, Canyon also provided all the pre-engineering, survey, project engineering, project management and ROV support associated with the work.
Amongst the major contractors, were FMC for subsea hardware, W Industries for subsea controls, Nexans for umbilicals, Bredero Shaw for pipeline insulation, Bay for mechanical topside modification and the MMR Group for instrument / electrical topside modification.