Post on 20-Dec-2016
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HYDROFEST 2010
GEOPHYSICAL SITE SURVEY
HYDROFEST 2010
GEOPHYSICAL SITE SURVEY
Presented by Mike LiddellChief Surveyor
Fugro Survey Limited
Presented by Mike LiddellChief Surveyor
Fugro Survey Limited
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INTRODUCTIONPRINCIPLES, METHODS AND TOOLSSITE SURVEY OPERATIONSRECENT DEVELOPMENTS -AUV SURVEY OPERATIONS
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Just about anything you need to put on or in the seabed; examples:– Exploration Surveys– Rig Site Surveys– Platform Site Surveys– Pipeline Route Surveys– Cable Route Surveys– Field Development Surveys– Clearance, Abandonment and
Inspection Surveys– Wind Farm Surveys
What do you need site surveys for?
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EXAMPLES OF SITE SURVEY REQUIREMENTS
WIND FARMS
SEMI-SUBMERSIBLE DRILLING RIGS PLATFORMS
PIPELINE ROUTES
SUB-SEA PRODUCTION
FACILITIES
ANYTHING THAT GOES ON OR IN THE SEABED…
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What are we trying to find out?– Water depths, seabed relief,
seabed gradients– Obstructions, debris, wrecks,
existing installations– Seabed sediment types– Shallow geology, foundation
design, trenching conditions– Geohazards such as shallow gas
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What if you don’t do a site survey?...
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What if you don’t do a site survey?...
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What if you don’t do a site survey?...
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What if you don’t do a site survey?...
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NORTH SEA SHALLOW GAS BLOWOUT
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NORTH SEA SHALLOW GAS BLOWOUT
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OFFSHORE EGYPT GAS BLOWOUT 2004
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PRINCIPLES, METHODS AND TOOLS
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BASIC PRINCIPLES
Use of geophysical ‘remote sensing’techniques, calibrated by some limited
‘ground truth’ sampling.Virtually always use acoustic methods
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Water depth measurement, seabed topography: >ECHO SOUNDERSingle BeamMulti Beam
Detection/identification of seabed obstructions: >SIDE SCAN SONARInterpretation of soil lithology, shallow gas detection: >SHALLOW SEISMIC
ACOUSTIC METHODS
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Echo Sounding
Single beam
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ECHO SOUNDERS
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100m
Multi-beam echosounder: Topographic Image
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SHADED RELIEF FROM MULTIBEAM ECHO SOUNDER
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ROUTE VISUALISATION FROM MULTIBEAM ECHO SOUNDER
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SIDE SCAN SONAR
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SIDE SCAN SONAR
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SIDE SCAN SONAR
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SIDE SCAN SONAR
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Seismic Systems: Principles
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PingersBoomersMini-airgunsCHIRPSparkers
SINGLE CHANNEL SEISMIC METHODS
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SINGLE CHANNEL METHODS
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SINGLE CHANNEL METHODS – Chirp profiler
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SINGLE CHANNEL METHODS – Chirp profiler
20 m
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SINGLE CHANNEL METHODS – mini-airgun
30 m
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MULTI CHANNEL METHODS
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MULTI CHANNEL METHODS
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MULTI CHANNEL METHODS
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HIGH-RESOLUTION 2D SEISMIC VESSEL
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3D SEISMIC – MAINLY USED FOR EXPLORATION
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3D SEISMIC – A lot of sensors to be positioned accurately
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3D Seismic Survey – result is a seismic “cube”
1000 m
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• Grab Samplers
• Gravity Corers
• Vibrocorers
• Cone Penetrometers
• Boreholes
GEOTECHNICAL SAMPLING
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Environmental SurveysJNCC guidelines necessitate environmental surveys in sensitive areas
• Pockmark fields – active venting encourages marine life growth and reef development
• Sabellaria – tube worms• Herring spawning grounds• “Reefs”
Seabed photos & sediment grab samples taken as part of geophysical surveyEIA becoming standard part of site surveysGeophysicists working with marine biologists
Sabellaria spinulosa
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INTERPRETATION AND PRESENTATION
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SEABED FEATURES CHART
Distribution of seabed sedimentsTopographic features (sands waves etc)Rock outcropsPockmarksExisting infrastructure; pipelines, cables etcWrecksItems of debrisSeabed Features Chart should comprise interpretation of Echo Sounder, magnetometer and side scan sonar data with seabed samples
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SHALLOW SOILS CHART
Map of depth to significant sediment interfaceIdentify soil profile in the required depth zoneLocate potential obstructions; boulders, gravel layers etcIdentify potential unconsolidated soils / loose sands – geotechnical weak units
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FOR PIPELINE ROUTES - ALIGNMENT SHEET FORMAT
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3D perspective
Shaded relief
Colour coded seabed gradient
SEABED VISUALISATION
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Seabed Features/Hazards map – Use GIS
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SITE SURVEYOPERATIONS
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• Construction of Survey Programme
• Positioning of Vessel
• Positioning of Sensors
• Quality Control of Bathymetry data
THE SURVEYORS ROLE
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SURVEY LINE PLAN FOR JACK-UP RIG
Distances in metres1 km
Plus tie line to adjacent borehole or survey area
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SURVEY LINE PLAN FOR SEMI-SUBMERSIBLE RIG
Distances in metres1 km
Plus tie line to adjacent core location or site survey
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AUV SURVEYS
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THE DEEP WATER SOLUTION
Traditional survey methods have numerous drawbacks to the acquisition of geophysical data in Deep Water areas.For deep water areas better resolution and better positioning is neededThe survey industry’s solution:
The Autonomous Underwater Vehicle (AUV)
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AUV OPERATIONS
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Fugro’s “Echo Surveyor” AUV
• Kongsberg HUGIN 3000.
• Semi-autonomous vehicle independently powered and controlled (cable free).
• Depth rated to 3000 metres.
• Aided Inertial Navigation System provides extremely accurate positioning.
• Positional accuracy of the AUV is less than 5 metres, significantly better than towed systems.
AUV OPERATIONS
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AUV DATA QUALITY
Bathymetry from 3D seismic data
AUV mounted multibeam echo sounder data
Improved bathymetry data
quality... …compared to
3D seismic
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AUV DATA QUALITYImproved sub-bottom profiler data quality...
2DHR Data AUV Chirp Data
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INTEGRATED INTERPRETATION STRATEGY
Bring together all data types and background information together on one platform – SMT Kingdom Suite
SMT
Multi-layer Sonar Mosaics
Shaded Relief Bathymetry
Chirp
2DHR / 3D
Contoured Bathymetry
Cultural Data
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INTEGRATED INTERPRETATION STRATEGY
Many features can only be properly characterised by the use of several different data types
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REPORT DELIVERY
Seabed FeaturesSMT
Interpretation Products
Shallow Soils
Shallow Geohazards
•hardcopy•PDF•CAD•GIS
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Thank You