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 & ROV Support Vessel

Pipelay Barge

Pipelay Vessel

Heavy Lift Vessels

Dive Support Vessel

Trenching Vessel

Trenching Vessel

Trenching Plough

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

Pipelay - Barge Guidance Screen

Welding of Pipe Field Joints

Critical Stages

• 4 operations of additional concern – start-ups – laydowns – crossings – curves

Startup

Startup Detail

Start-up - Transponder Deployment

Laydown

Crossing - Preparation

Crossing

Curves

Pipe Design Route

Barge Track

BargeLeavingCurve

BargeEntersCurve

Tug Management

Anchor Barge Setup

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

Mature Field

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

As Laid Chart

Sub sea installations

Tordis subsea processing structure

Sub sea installations

Positioning packages

USBL / LBL Transponders

Batteries

Gyro Inclinometer

ROV readable display

High Precision Depth Sensors

Subsea Mux

Sub sea installations

Heavy lift

• Instrument Sledge • Gyro • Inclinometers • Data Telemetry

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.

Heavy Lift