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