Pipelay & Construction Support
Pipelay and Construction Support HYDROFEST 2014
Malcolm Gauld Chief Surveyor
Fugro Survey Ltd.
The Hydrographic Society in Scotland
Introduction
• Many construction activities requiring survey services
• North Sea development began mid-1960s • 1000s of km of pipelines laid • 1000s of structures installed
Phases of Construction
• Pre Installation Operations • Construction Operations • As Built Surveys • Trenching / Rockdumping • Post Trench Operations
Vessels
• Survey Vessel • Pipelay Vessels • Heavy Lift Vessels • Dive Support Vessel (DSV) • Trenching Vessels
Survey Vessel Personnel
Project Manager
Offshore Vessel Manager
Vessel Master
Client Representative
Surveyor
Survey Engineer
ROV Team (3)
Report Co-ordinator
Data Processor
Survey Engineer
ROV Team (3)
Data Processor
Surveyor
Day Shift Night Shift
Barge Survey Personnel
Project Manager
Party Chief
Barge Superintendent
Client Representative
Surveyor
Survey Engineer
Survey Engineer
Surveyor Day Shift Night Shift
Vessel Equipment
• DGNSS Receivers • Nav Suite Computers • North Seeking Gyro • USBL System • USBL Transponders • INS Systems • Long Baseline System • LBL Transponders
• Temp/Salinity Probe • Multi Beam Echo Sounders • Dual Channel Side Scan • Sub Bottom Profiler • ROV System with Sensors • Offline Processing System • Inter vessel data exchange
Survey Operations
• Conducted from Survey Vessel
• Prelay Survey of site for pipe or structure • Transponder Array Installation & Calibration • As built surveys • Pre & Post Trench surveys
Pre-installation Survey
• Ensures route / site is free of obstructions • Side Scan Sonar • ROV centre line / site visual survey • Swathe Bathymetry
– Digital Terrain Model – Route Topography Analysis – Array visibility Analysis
Transponder Arrays
• Use for precise positioning control • Preparation for Construction Phase
– Transponder Deployment – Baseline Measurement – Absolute Calibration – Network Adjustment
Example Transponder Array
Proposed Line
Box-In Transponder
Array Transponder
Jacket Transponder Platform
Construction Operations
• Pipelay Barge Navigation • Tug Management • Touchdown Monitoring • Heavy lift vessel positioning • Acoustic positioning USBL or LBL of structures • EDM (Total Station) positioning of structures
Barge Navigation
Pipelay • Ensure pipe is laid along design route • Concerned with heading and cross track distance
Construction • Ensure vessel at correct location and heading
Tug Management
• Required for anchored barges • Provides monitoring and planning of anchor drop
positions • 3 to 6 Anchor Handling Tugs • Tug position & heading data radio telemetered to
Barge
Touchdown Monitoring
• ROV Visual Survey of Pipe Touchdown • Data telemetry to Barge • Video telemetry of ROV camera picture
As Laid Survey
• Purpose - to check – pipe laid within tolerance – without significant damage – determine if remedial work is required
• ROV Visual Inspection • Charts and Report • Move to digital reporting
Sub sea installations
Positioning packages
USBL / LBL Transponders
Batteries
Gyro Inclinometer
ROV readable display
High Precision Depth Sensors
Subsea Mux
Heavy Lift
Prism targets are surveyed in relative to Structure reference point.
When installed use Total Stations on nearby platform or installation vessel to position new structure
Heavy Lift
Levelling Plates.
When structure installed these are used to create level plane to allow cutting of top of legs to accept modules.