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seabed-to-surface
NASNet Operational ExperienceFRADE Project, BrazilHydrographic Society in Scotland
23rd April 2009
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North America and Mexico (NAMEX)
Regional Profile
Operating in the Gulf of Mexico and the Caribbean, undertaking a range of construction and installation engineering services.
NAMEX divides its current business into 3 principal areas of operation:
Subsea Umbilical Risers and Flowlines (SURF)
Inspection and Maintenance and Repair (IMR)
Conventional Field Development and Trunk lines
The NAMEX region is focused on and ready for deepwater SURF projects and IMR
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DTM Brazilian Continental Shelf
FRADE
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Frade field developmentThe Frade field is 6 Km x 4 KmThe water depth at the FPSO is 1000 meters to 1400 at the East extent of the field 8” Gas I/E Pipeline from the FPSO to termination 41Km SW in water depth 130 meters – PRA1 PLEM –Acergy Installed
The development consists of :22 Riser Anchor Piles17 Production Flow Lines9 Gas Lift Lines10 Water Injection Lines 17 UmbilicalsFlexible Jumpers, Flying leads
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LBL RequirementsProvide LBL coverage over the entire construction area with an relative accuracy of <2 meters and 0.5 meters RMSCapacity to operate on the seabed for the entire construction period and beyond without recovering for battery changesPotential to accommodate multi vessel users (SIMOPS)Straightforward to deploy and manage
System ConsiderationsCostReliabilityMethodSupport
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NASNet
Advantage - Disadvantage
Fewer stations to deploy and calibrate – savings in vessel time
Reduced calibration time –savings in vessel time
Simplified array management
Reduced O/P power levels –Longevity of operating time with Lithium battery packs
Quicker update rate of position
New and untried technology with no commercial experience
Vessel modifications required to operate the NASNet system
Software routines needed to be changed to make the system more effective
Additional training of personnel to operate the system
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Original Proposal
System uses Acoustic Spread Spectrum TechnologyOperating principle is similar to GPS in that each station transmits information on a regular basisSignal includes accurate time, error correction and station informationUnlike Transponder systems where an interrogation signal has to be transmitted, NASNet receivers only have to listen
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NASNet 8 Station Array
WE LL C
3TXCO3DB
4TXCO2D
OUS2
GT-203A
3RJS416
1RJS366
WELL C
MUS2
GT-220
N5I1
N5P1
ODI1
MDI1
OUI1
MUI2
MUI1
OUI2
MDP1MDP2
MUP4
ODP1
OUP1
OUP3
OUP2
MUP2
MUP1
MUP3
ODP3(NOTE 3)
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NASNet Field proposed with 16 stations
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Acoustic Challenges
SVPPositive going sound velocity close to the seabed causing the acoustic signal to bend towards the surface
TopographyThough the construction area has no great features there is a general slope from West to East of 3 ° with slope increasing in areas of the water injection loop to 5 °-Because of this we get ground absorption up slope and the signal bending away down slope.
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Acoustic Analysis Predicted cover 28 Stations
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Acoustic Analysis – Predicted cover 22 Stations
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NASNet 22 Station Array with 6 Optional
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Frade ProjectInitial DeploymentThe initial deployment was 8 stations to enable installation of the Riser Anchor Piles around the FPSO location.
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Frade ProjectInitial DeploymentThe initial deployment was 8 stations to enable installation of the Riser Anchor Piles around the FPSO location.Each deployment and calibration was completed in 3 hours.
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Frade ProjectInitial DeploymentThe initial deployment was 8 stations to enable installation of the Riser Anchor Piles around the FPSO location.Each deployment and calibration was completed in 3 hours.Position check after calibration on an existing wellhead
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Frade ProjectInitial DeploymentThe initial deployment was 8 stations to enable installation of the Riser Anchor Piles around the FPSO location.Each deployment and calibration was completed in 3 hours.Position check after calibration on an existing wellheadSet a construction receiver on the seabed in the center of the array to monitor the integrity of the array
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Frade ProjectInitial Deployment
The initial deployment was 8 stations to enable installation of the Riser Anchor Piles around the FPSO location
Each deployment and calibration was completed in 3 hours
Position check after calibration on an existing wellhead
Set a construction receiver on the seabed in the center of the array to monitor the integrity of the array
Results of the calibration and confidence check
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Eight Beacon Array Calibration and Confidence Check
Object Easting Northing Range3TXC03DB 412772.00 7579292.00NASnet 412764.16 7579294.75
Heading098 412766.23 7579294.59188 412764.86 7579294.10278 412764.59 7579296.77008 412766.32 7579294.38
Med 412765.55 7579294.49Max 412766.32 7579296.77Min 412764.59 7579294.10Rng 1.73 2.67Std 0.90 1.22
Diff. -1.39 0.27
Well Diff. 7.84 -2.75 8.31 NASnetWell Diff. 6.46 0.27 6.46 HIPAP
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Pre Lay Survey
Deployment of the remaining Stations to complete the 22 station array
Box in Calibration of the remaining stations
Installed two additional Construction receivers across the field
Conducted Pre lay survey of the Frade Development area
Logged NASNet coverage over all the flow line routes and Well locations
Checked the positions of the four existing wells
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NASNet Installation - Normand Mermaid
NASNet Surface Controller Gate Valve and Hoist
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Construction Receiver on a modified MS Stand
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Existing WellsAUV-NASNet-SSBL
2.8311.533.62513.725Difference
7578109.2413943.57578108.4413941.375781124139554TXC02D
-3.826.24-2.597.51Difference
7579294.49412765.557579294.75412764.167579292.00412772.003TXCO3DB
-2.12-0.42-2.35-1.71Difference
7578926.12415641.427578926.35415642.7275789244156413RJS416
2.50-5.093.48-5.38Difference
7580613.5412979.17580612.5412979.475806164129741RJS366
NorthingEastingNorthingEastingNorthingEasting
HIPAPNASNetAUV SurveyWell #
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Tracking comparison HiPAP USBL/NASNet
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NASNet Position Solution CRx and ROV
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Conclusions: System and Project Evaluation Summary
Robust and stable positioning meeting specification expectations
Uniform positioning regime over entire field
Highly acceptable cycle time
Simultaneous users – True multi user system
Improving / growing technical support
Improving system technical reliability
Joint planning and preparation is “a must”
Difficult to establish multi user operating responsibilities unless managed by Client
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Lessons LearntPlanning
Seabed Topography and Velocity analysis
TrainingOperator level & higher understanding of acoustic principles
Support Develop a support & communications structure for remote operations
TechnicalSeabed stability, moorings etcVessel preparationDealing with technical difficulties in a structured and constructive mannerSimOps need some degree of management
CommercialHanding over of network, client understanding.Acceptance and expectations of other usersClient free issue? – contractual concerns
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