MCE Deepwater Development 2016 PAU, FRANCE • 5-7 APRIL 2016 Record-setting AUV pipeline inspection in deepwater west Africa Sébastien GHIS
MCE Deepwater Development 2016
PAU, FRANCE • 5-7 APRIL 2016
Record-setting AUV pipeline inspection
in deepwater west Africa
Sébastien GHIS
MCE Deepwater Development 2016
Objectives
• measure the water depth variations and slope changes along all in-field pipelines,
• create photo imagery mosaics along all in-field pipelines, FLETs and ILTs,
• create accurate 3D modelling of pipelines and adjacent seabed for free span assessment,
• establish a baseline for future surveys aiming to assess pipe displacement (lateral or upheaval buckling, etc.),
• identify areas of interest for further ROV detailed inspections,
→Survey company
Pipeline baseline survey Plan view
Longitudinal profile
Cross profiles
MCE Deepwater Development 2016
ROV: Key information
Remotely Operated Vehicle (ROV)
• Remotely operated from the surface by pilots,
• Physically linked to surface vessel via main lift umbilical and tether, providing power supply and data transmission,
• 22 hours of operability per day,
• Average speed: 0.5 kts for a Work class ROV,
• Limited number of survey sensors carried on a WROV without dedicated survey skid,
• Intervention possible (debris removal),
• Navigation in the subsea facilities immediate vicinity is safe,
• Cathodic protection measurements possible.
MCE Deepwater Development 2016
AUV: Key information
Autonomous Underwater Vehicle (AUV)
• No physical link to the surface,
• Operates pre-programmed missions close to seabed,
• Acoustically linked to the vessel,
• Dive duration (from 20 to 48 hours),
• Important number of survey sensors carried,
• Acquisition speed of 3.5 to 4.5 knots,
• Smoothed linear trajectory,
• No physical contact with subsea facilities required,
• Power supplied by batteries,
• Data downloaded via fiber optic cable once AUV on deck,
MCE Deepwater Development 2016
Existing facilities:
• Surface facilities; FPSOs and OLTs,
• Subsea facilities; SSU, Manifolds, Spools, X-Trees,
Well Jumpers, riser towers, dynamic pipelines,
→ Adapted procedures and data base up to date
Other operations ongoing:
• Offloading : 1-2 Tanker per week on each FPSO (including tandem operations),
• MODUs (Mobile Offshore Drilling Unit),
• FSVs (Fields Support Vessels) installing X-Trees and Well Jumpers,
• installation vessels working an OLT, laying some umbilical and doing heavy lift,
• seismic vessel shooting a 4D seismic.
→Dedicated planner
Operations at sea – actual constrains
MCE Deepwater Development 2016
• Surface and subsurface geophysical data for development engineering
• High resolution seabed mapping – Multibeam Echo sounder (300 kHz)
• Seabed features detection – Side Scan Sonar (120 kHz)
• Shallow subseabed characterisation – Sub Bottom Profiler (1.5-4.5 kHz)
• Acquisition characteristics
• Integrated positioning system
• Acoustic data link
• Acoustic command link
• Limitations
• Power supply (battery)
• Launch & recovery system
Conventional survey key acquisition parameters
MCE Deepwater Development 2016
Data quality examples – Bathymetry and backscatter
• Manifold
Bathymetry (MBES)
Bathymetry (MBES) & Backscatter (SSS)
MCE Deepwater Development 2016
• High resolution sensors for pipeline inspection:
• Laser Micro-Bathymetry system
(range resolution of 5 mm & 5 mm footprint).
The system collect 1400 samples per scan (a repetition rate of 29 Hz)
• Camera
High Resolution Digital Camera (Image resolution 4.4 mm).
Seabed coverage at 8 meter altitude: 6.0m x 4.5m (capture rate : 1.75s).
• Acquisition characteristics
• Power supply (battery)
• Download of data
Conventional survey key acquisition parameters
MCE Deepwater Development 2016
Data quality examples – micro bathymetry
• Subsea laser - micro bathymetry
Spool
FLET
Trench
MCE Deepwater Development 2016
Data quality examples – Photography
• Digital stills and photomosaic
• combines the benefits of visual imagery and photomosaic, to produce a large-scale overview of the field.
• Camera specifications:
• Survey speed @ 4 knots
• 1360x1024 pixels
• 6x4.5m coverage @ 8m
• 5 mm resolution
• Still picture every 1.7sec with 30% overlap
MCE Deepwater Development 2016
Data quality examples – Combined laser and photos
MCE Deepwater Development 2016
GIS tool for data review
• Objective
• Integrate all data recorded by AUV in single Geographical Information System (GIS ),
• Identify areas of interest for further detailed ROV survey,
• Facilitate analysis by pipeline specialists and inspection teams,
• Having an integrated support tool for subsea integrity– time lapse monitoring.
MCE Deepwater Development 2016
Results examples – GIS products
MCE Deepwater Development 2016
AUV Deep water subsea layout baseline survey
• Sensors are fully qualified and inspection AUV is fully operational,
• Provides subsea layout integrity review with optimal spatial resolution,
• Provides solid GIS products for subsea IRM planning and further dedicated ROV visual investigation,
• Provides a database which could be used for a “time lapse” approach in order to detect any seabed geohazard and subsea equipment modification during “life of field”,
• AUV pipeline inspection surveys may not fully replace ROV inspection surveys,
AUV deep-water subsea integrity surveys shall be promoted for existing “brown field” or forthcoming layout
Conclusions
MCE Deepwater Development 2016
Thank you for your attention!
Questions and comments are welcome!
MCE Deepwater Development 2016