1. First Permanent Polyester
Prelay on the Seabed in
Gulf of Mexico
Todd Veselis

2. Objective
• History of polyester on the seabed
• Discuss of why we took this approach for Mirage
– Advantages
– Concerns?
• Review the polyester prelay approval process
• Review the test plan and results

3. Project Overview
• Field: Mirage (MC-941) /Telemark
(AT-63)
• Owner: ATP Oil and Gas
Corporation
• Water Depth: 4,000 ft
• Hull Type: Deep Draft Floating
Platform (DDFP) – MinDOC3
• Installation: 2009

4. History of Laying Polyester on Seabed
• Industry testing – late 1990’s
– Came as a result of industries
work w/polyester
– Various JIPs
– Lab tests
• Inadvertent contact during
– Installation
– Service
• MODU moorings
– Began in 2007
– Field trials
– Industry experience

5. NTL 2009-G03
• Issued in Jan 2009 by BOEM/BSEE
• Provides guidelines for permanent and MODU
moorings
• Establishes conditions for presetting moorings on the
seabed including:
– Use of ropes with proven filter barrier
– Following recommendations in APR RP 2SM
– Site survey
– Rope inspection criteria

6. Advantages to Prelaying Polyester
on Seabed
• Timing
– Allows mooring to be set off critical path and at any time
– Allows for changes in hull sail away/installation
• Installation
– Eliminates need for handling surface/submersible
buoys
– Eliminates risk of collision/loss of buoy
– Allows all polyester to be handed during single
campaign
• Hookup
– Eliminates the need to install polyester during hookup
– Increased hookup efficiency
– Increased flexibility

7. Approval Process
• Process was somewhat
undefined because:
– First permanent mooring
application where
polyester was
intentionally laid on
seabed
• Goal was to:
– Demonstrate, through
testing, that seabed
contact would not have
any adverse affects

8. Approval Process
• Satisfy requirements of NTL 2009-G03
• Submission of test plan to
BOEM/BSEE (formally MMS) for
approval
– Field test
– Subrope testing
– Lab testing
• Submission of test results to
BOEM/BSEE

9. Field Test
• Lowered two test sections
onto seabed using AHTS
(Anchor Handling Tug
Supply) vessel
• Performed two drag tests with
inserts, each a minimum of 5
min with 5 min in between
• Left inserts on seabed for 24
hrs
• Recovered inserts to surface

10. Subrope Testing
• Modulus testing
– 10th cycle (10% - 50%)
– EA/MBL (Stiffness/Min. Break
Load)
• Break testing
– Four control samples – (C)
– Four insert samples – (I)
• Fatigue testing
– 80,000 cycles
– Load range – 15%-45%
– Sample consisted of 3 full
scale subropes

11. Subrope Testing – Results
• Control and insert
samples average break
strength and modulus
were within 1% of each
other
• Sample survived 80,000
cycle fatigue test without
issue

12. Subrope Testing – Results
Breaking Strength Modulus 10th Cycle 10-
Sample (kips) 50%
(EA / MBL)
C.1 383.8 14.7
C.2 411.0 15.3
C.3 398.6 14.3
C.4 419.9 14.8
I.1 417.3 14.2
I.2 402.9 15.5
I.3 381.8 14.9
I.4 399.2 15.1
Mean Control Sub-ropes
403.3 14.8
(C.1-4)
Mean Insert Sub-ropes
400.3 14.9
(I.1-4)

13. Lab Testing
• Inspection performed on
both control and sample
yarns
• Inspection included:
– Visual Inspection
– Fiber Testing
– Yarn Analysis
– Tenacity
– Strength
– SEM (Scanning Electron
Microscope) Photographs

14. Lab Testing Results
• No significant difference
in:
– Break strength
– Modulus
– Wet yarn on yarn abrasion
– Visual appearance
• Yarn from both samples
looked new
• In very rare cases trace
particles were found in
outer core yarns

15. Conclusion
• Testing demonstrated that:
– Soil filter was effective
– Contact with the seafloor had no
adverse affects on the polyester
• For Mirage, prelaying on the
seabed:
– Saved time during hookup
– Reduced risk

16. Contact Information
Todd Veselis
InterMoor
Email: todd.veselis@intermoor.com
Phone Number: 832-399-5018