The first large-scale template-based subsea production system to be installed beyond the practical depth for diver intervention was set in February 1987 by Placid Oil Company in Green Canyon, Block 29, in the Gulf of Mexico at a depth of 450+ m The installation relies heavily on remote-work system intervention and support for both operation and maintenance The system consists of a 24-slot main production template producing through a fixed buoyant riser to a floating drilling/production semisubmersible permanently anchored overhead Future satellite templates are planned which will produce back to the main template
The remote work-system which will be used will be a fully founded, dual-manipulator, electrohydraulic, work-capable remotely operated vehicle (ROV) In some cases the remote work-system is used as a back-up/secondary means of operation In many instances, however, it provides the primary and often the only facility for operation of the subsea components The concept of using the remote work-system as the delivery vehicle for subsea valve operators allows the operators to be easily removed to the surface for maintenance and repair It also eliminates the costly and often complex task of designing components for a 20+ year life In a fully submerged condition The design parameters which were used for this development are summarized below
Gulf of Mexico
Water depth 500–1000 m
Semisubmersible work platform
Fixed buoyant riser
24-slot main template
Pipelines to shallow-water platform
Four ea 4-slot satellite templates
ROV support-HYDRATm 1000
The intervention tasks to be performed by the remote work-system evolved over a period of months The tasks cover the spectrum of underwater activities from installation through long-term operations Some of the work tasks required that hardware be developed Others required procedure development A list of the intervention tasks by major subsea component follows This list outlines only work tasks Inspection tasks-of which there are many-are not included
Main Template
Lift sling disconnection and removal*
Pipeline ball valve operations*
Pig trap isolation valve operations*
Pig trap launching valve operations*
Ball-valve stem lubrication*
Ball-valve sealant injection*
Guidepost replacement*
Guidewire establishment*
Shuttle-valve operation and replacement*
Anode replacement*
Pipeline/flowline pull-in
Template/Satellite Trees
Hydraulic gate-valve override-production master valves, annulus master valves, wing valves
Needle manual gate-valve operations*- isolation, chemical injection, testing, tree cap
Sealing-ring replacement*
Connector overridelrelease
Production Riser
Air-valve replacement*
Control umbilical installation/replacement
Installation guidewire removal*
Control Pods
Needlelball-valve actuation*
To enable the remote work-system to perform some of these tasks required that certain hardware be developed Most of this hardware took the form of valve actuators for various types of valves and widely varying torques. A list of the hardware designed and produced is shown below.
