An Overview of Seabed Surveys (High resolution Geophysical Site Surveys)

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1 An Overview of Seabed Surveys (High resolution Geophysical Site Surveys) Anna Fulop Chief Geoscientist Fugro Survey Limited 22 April 2015

2 Agenda Introduction Site survey - purpose and requirements Principles, Methods and Tools AUV Surveys Site Survey Operations Interpretation and Presentation

3 Introduction - The Fugro Group Dutch multinational company; headquarter in Leidschendam, NL. Fugro provides People, Equipment, Expertise and Technology worldwide; Approximately 12,000 employees in over 60 countries. Activities: acquire and interpret Earth s surface and sub-surface data to support the design, construction, installation, repair and maintenance of infrastructure, on land and at sea. 3 Divisions (Geotechnical, Survey and Subsea Services) each containing numerous individual Operating Companies (OpCos). Survey division: Oil & Gas industry, Renewables, Mining, etc

4 Introduction Fugro Survey Division Meteorology and oceanography, Weather forecasting Offshore structural monitoring Marine environmental services Geophysical Survey, cable route and hydrographic survey Construction survey support Satellite positioning, monitoring and mapping Aerial mapping, Terrestrial surveying Geospacial GIS solutions Fugro Survey Limited High-resolution marine geophysical site surveys (Oil & Gas industry) - seabed mapping, drilling hazard surveys, regional and deep-water surveys, pipeline route surveys Offshore positioning services and construction support - rig moves, pipelay operations, etc Main office in Aberdeen Operate worldwide, but predominantly in NW European Continental Shelf (UKCS, NOCS, Dutch and Danish sectors), offshore West Africa

5 Site surveys - purpose and requirements A survey is required for anything that is moved from one place to another (e.g. rig move, site clearance/abandonment) is laid on the seabed (e.g. pipeline, power/ telecommunication cable) has foundations in the seabed (e.g. platforms, buried pipelines, wellheads, manifolds, anchors, offshore wind turbines) might affect environmentally sensitive areas may be affected by geohazards or offshore or fishing activity goes on or in the seabed

6 Site surveys - purpose and requirements A survey will determine: Seabed conditions - Bathymetry: water depth, gradients, relief - Seabed sediment types (clay, sand, gravel, bedrock) - Seabed obstructions (existing infrastructure, wrecks, debris, boulders, UXO) - Potentially sensitive habitats (e.g. coral, herring spawning grounds, MDAC) Sub-seabed conditions - geology - foundation / anchoring conditions - trenching conditions Potential Geohazards - Slope stability - Faulting - Probability of shallow gas Are these conditions suitable and safe?

7 Seabed Conditions - Bathymetry Iceberg ploughmarks, northern North Sea Megaripples and spud can depressions, southern North Sea Pockmark, central North Sea

8 Seabed Sediments and Features Sand with rock outcrop Pipelines with associated infrastructure; soft clay with numerous pockmarks

9 Seabed Sediments and Features Unexploded Ordnance (UXO)

10 Seabed Sediments and Features Abandoned telecom cable near proposed drilling location (not mapped) Debris (cable / wire)

11 Environmentally Sensitive Habitats (DECC requirements in the North Sea) Seabed photograph of Coral colonies Area of possible Coral on SSS data

12 Sub-seabed Conditions

13 Geohazard Identification Seabed Stability Evidence of slope instability

14 Geohazard Identification - Faulting 500m Evidence of faulting on 2DHR seismic data

15 Geohazard Identification Potential Shallow Gas 500m

16 What are the risks of not doing a site survey? West Vanguard Blowout, NOCS (1986) Punch-through

17 Principles, Methods and Tools Basic Principles Use of geophysical remote sensing techniques Predominantly use acoustic methods - Range of equipment and methods - Range of acoustic frequencies Calibrated by some limited ground truth sampling - Geotechnical - Environmental Platform: dedicated survey vessels vs vessels of opportunity

18 Echo Sounders Single and multibeam systems, generally hull-mounted Water depths measurements Topography SINGLE BEAM

19 Side Scan Sonars High, low, dual frequency towed systems Measure seabed reflectivity Detection / identification of seabed sediment and obstructions Measurement of dimensions (particularly height above seabed)

20 Side Scan Sonar Data seabed sediments Fine SAND Rippled SAND Boulders/ Clay outcrops Fine SAND Rippled SAND

21 Side Scan Sonar Data detailed mapping of seabed obstructions Anchor scar with pit Small depression Surface-laid pipeline Uncharted WRECK L=33m, W=6m, H=3.3m Acoustic shadow Area of debris Seabed

22 High-resolution Seismic Systems Used for sub-seabed mapping Seismic reflection Single-channel systems: - Pingers (generally hull-mounted) - Chirps (towed / hull-mounted) - Boomers / Sparkers (towed) - Single airguns (mini gun and single channel streamer)

23 High-resolution Seismic Systems (cont d) 2D high-resolution multichannel seismic - typically 140 cu.in. sleeve airgun source fired at 6.25m / 12.5m intervals - 48 / 96 channels, 600m / 1200m hydrophone streamer - Digital recording system - Extensive data processing required - Deeper penetration and increased signal / noise ratio

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25 Summary of Acoustic Methods

26 Other Tools and Survey Methods Complement the acoustic geophysical survey data Magnetometer, Gradiometers Geotechnical testing/sampling - Grab sampler - Gravity / Piston Corer - Vibrocorer - Cone Penetrometer Testing (CPT) - Deep boreholes (>30m bsb)

27 Other Tools and Survey Methods (cont d) Environmental Surveys - Underwater camera: sills and video transects - Box coring Have become standard part of most seabed surveys

28 AUV Surveys Deep Water Solution Traditional survey methods have numerous drawbacks to the acquisition of geophysical data in deep water areas: - Deployment / recovery difficult in bad weather conditions - Noise / weather effects, vessel motion - Limited penetration and data resolution (hull-mounted systems) - Sensor positioning imitation (acoustic positioning for towed sensors) For deep water areas, better resolution and better positioning are needed The survey industry s solution: The Autonomous Underwater Vehicle (AUV)

29 Fugro s Echo Surveyor IV AUV Kongsberg HUGIN 1000 Semi-autonomous vehicle independently powered and controlled (cable free). Depth rated to 3000m. Aided Inertial Navigation System provides extremely accurate positioning. Positional accuracy of the AUV is less than 5m, significantly better than towed systems.

30 Improved bathymetry data quality Bathymetry from 3D seismic data AUV mounted multibeam echo sounder data

31 Improved sub-bottom profiler data quality 2DHR Data AUV Chirp Data

32 Improved seabed imagery quality With option to mosaic images

33 Site Survey Operations Onshore Vessel PM, main point of contact between survey vessel and client Geoscience Team Leader Offshore Full Survey Team 24 hour operations 1 Party Chief 2 Online Surveyors (Day/Night) 1 Technical Coordinator 4 Engineers (Day/Night) 1 QC Geophysicist 1 Environmental Scientist Optional requirements:2nd Geophysicist, Processing surveyor, Seismic processor, Gun mechanic, Geotechnical survey crew

34 Interpretation and Presentation Data interpretation Variety of software used for the different datasets Large volumes of data handled Integration of all available data essential suitable software required Final Product Site Survey Report Comprehensive, structured and high-quality survey report Often includes integrated geophysical, environmental and geotechnical results Detailed figures and charts showing the final interpretation Digital deliverable (CAD files, GIS deliverables)

35 Summary Geophysical site surveys are essential to ensure the suitability and safety of sites for offshore infrastructure construction During a site survey a large amount of information on the seabed and subseabed environment is acquired A detailed and integrated interpretation is required to turn this information into a high quality site survey report for the end user The requirements vary from project to project; techniques, data quality and level of interpretation have to match these requirements

36 Thank you Any Questions?