FPS MOORING INTEGRITY JIP - STATUS UPDATE

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1 FPSO Forum, 27 th October 2004 FPS MOORING INTEGRITY JIP - STATUS UPDATE Martin G. Brown Principal Naval Architect Noble Denton Europe Ltd. Aberdeen, UK mbrown@nodent.co.uk Tel. +44 (0) Mobile +44 (0)

2 JIP Objectives Assess how long term moorings have performed in the field Feedback operational and inspection experience to the industry & to mooring designers Publicise the importance and potential vulnerability of mooring systems Disseminate best practice guidance Help to safeguard the long term reputation of FPSO/FPS industry by reducing the danger of mooring failure

3 Key Points Full results still confidential Worldwide assessment of FPSOs, Semi subs and Spars Difficult getting data and the task is not complete, more assistance needed Very strong Steering Committee & the meetings have been very useful mechanism for information exchange

4 Well Supported 1. ABS 2. Ansell Jones 3. Balmoral Group 4. Bluewater 5. BP 7. Bureau Veritas 8. Chevron Texaco 9. ENI (Agip) 10. HSE 11. IMS/Craig Group 12. Lloyds Register 13. Marin 14. Maersk/North Sea Production 15. Norsk Hydro 16. Offspring International 17. Petro Canada 18. SBM 20. Statoil BUT a few key organizations missing

5 Int. Survey Past & Present Results Sept Hurricane Ivan, 5th generation semi Deepwater Nautilus broke ALL fibre moorings & free drifting

6 2003 Chain Run Out N. Sea FPSO Serious uncontrolled incident, potential for bad injury or fatality, emergency shutdown with personnel to lifeboat stations Added danger of damage to sub sea assets Note - semi sub units have suffered from chain run outs Gypsy Wheel Arrangement before Failure Gypsy Wheel pulled off mountings after failure

7 1994 Multiple Line Failure HSE Report extract In 1994 on N. Sea FPSO a second chain parted. Held station on thrusters, production shut down, wells shut in, during adverse weather anchor lines no. 2,3,4 and 7 parted

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9 Fulmar SALM 3,700t SALM inc. pipes & yoke Fatigue failure 7 years at base of column (wedges) Sea bed hole either side of Forties pipeline!

10 Past & Present Survey Results A number of semis experienced multiple line failures

11 Past & Present Survey Results 1981 (after 6 years on station) broke free Drifted for 1.5 days before being secured by a towline Covered some 27 miles from original position

12 LOADING MECHANISMS Mooring is a very difficult dynamic problem After 20+ yrs must still withstand 100 yr storm! Bending & Tension Corrosion Highest Tensions Impact & Abrasion Wear and fatigue

13 Long Term Degradation Heavy corrosion inc. 2 to 3mm pits, isolated areas deeper NOTE Leeside failure

14 Note apparent grinding action on inner side of link see red arrow

15 Finite Element Stress Contour Plot

16 North Sea Wear Rate Implications Line failed in the thrash zone and a number of links close to the break were recovered back to shore. Dimensional checks of the most worn areas of this chain gave a wear rate of 0.6 mm/year in the thrash zone. This is 50% higher than the value specified in OS E301. Implications for real long term integrity, even for relatively benign climates, but more data needed Both wear and corrosion need to be considered at the same time

17 Wear at Turret base External cantilevered bow turret mooring Chain chafing on the welds in the hawsepipes UMPHE wrapped round the chain to stop wear

18 Checking Connection to FPSO

19 Overcoming Access Problems A lot can be achieved by inspection if done carefully and refinements are made to existing technology

20 Overcoming Access Problems

21 Connector Problems Connector disconnected itself subsea resulting in line failure

22 Retrofitted Anodes

23 ROV Video Grabs

24 Weighted Chain Behaviour General Location of Damaged Shackles General Location of Excessive Wear

25 Hanger Shackle Pin Wear

26 N. SEA FPSO CLUMP WEIGHTS

27 FPSO Midline Buoys Failure Loss on leeside lines Line 10, shackle buoy failed, 2001 Line 1, shackle buoy failed, 2004, sea bed wire corroded Line 2, buoy chain cracked & replaced Line 3, buoy chain failed

28 Girassol Buoy Mooring Failure Friction induced tension bending fatigue Implication for taut moored systems in deep water

29 Brent Spar Successs! 1976 to 1995 (19 years continuous service!)

30 Brent Spar Experience Localised wear on the chain, where it sat on the stopper Indentation from where the chain bears on the Stopper

31 Failure Detection Implications Failure to detect Or Reinstate Severe Weather Single Line Failure System Failure Gross Wear/ Degradation Multiple Line Failures Offset monitoring limited benefits unless deep water

32 Detecting Line Failure Hull-mounted Sonar: hard wired magnetically mounted sonar heads; single screen permanent display with built-in alarms; 5 second refresh rate; one head able to provide majority coverage (for redundancy) by cancelling time bar on displayed echoes; Need assessment of in field tests

33 Conclusions Past incidents & present concerns illustrate the need to guard against complacency Also cost of single mooring line failure high, 1.3M for bpd N. Sea FPSO to 7M for large W. African unit Break test data is needed on worn chains/wires/connectors High quality inspection is vital for ensuring long term integrity Think of moorings as relatively delicate primary structural members which in their 20 th year may need to withstand 100 year return survival conditions Is it realistic to expect moorings to last 20+ years, particularly when permanently locked off?

34 Mooring Integrity Future Still time to join & contribute to the survey and the JIP report Plans for Moorings User Group (MUG) meet annually as part of FPSO Forum MUG will review experiences from the last 12 months and commission new work as required

35 FPSO Forum, 27 th October 2004 TROPICAL FLOATING PRODUCTION - COLD WATER PIPE (CWP) RESEARCH PROPOSAL Martin G. Brown Principal Naval Architect Noble Denton Europe Ltd. Aberdeen, UK mbrown@nodent.co.uk Tel. +44 (0) Mobile +44 (0)

36 PRECURSOR TO AFTERNOON SESSION ON LNG FPSO LNG Tanker LNG Plant FLNG

37 Introduction Floating LNG & tropical FPSOs need lots of cold, pure sea water for process cooling This water available at 500m+ below you Number of process studies have assumed that this water is readily available because: Cold water gives substantial OPEX & CAPEX process cost reductions Shell s offshore LNG GameChanger TM relies on deep sea water cooling Girassol FPSO identified substantial saving on Water Injection sulphate ion removal process but too late to be incorporated

38 Cold Water Source Tropical oceans surface temperature > 28ºC at 700 to 1,000m about 4ºC all year round due to the thermocline Deep water is relatively pure and free of pathogens so biofouling of process equipment will be less

39 Possible Locations of future Offshore LNG Production Facilities Benign, continuous directional swell Hs 4 6 m, soft soils Nigeria Shell Sunrise Timor Sea (100 m) Benign, infrequent cyclones Hs 7 8 m, competent soils Offshore Indonesia Possible Prospect

40 Warm Surface Water

41 CWP Design Challenges Know from previous work on Ocean Thermal Energy Conversion (OTEC) that CWP have had problems Challenges of installing & maintaining 500+m long CWP for 20+ year operation Companies need to know that such a pipe is feasible & it will be reliable if works saves money & provides good GREEN publicity

42 CWP Dimensions CWP diameter depends on flow rate, 50,000 tonnes/hr Results in a diameter possibly in excess of 2m (6.6 feet). Ideally deployed CWP from the FPSO to save installation costs and also to make inspection & maintenance cheaper Tow & upend another possibility similar to Girassol riser towers

43 Environmental Aspects Artificial form of natural upwelling bringing up nutrient rich water from the depths Hawaii has been continuously pumping from depths since 1979 Aquaculture Beds Cold Water Pipe

44 French Pioneer Georges Claude L'énergie thermique des mers (ETM) or OTEC

45 French Pioneer Georges Claude 1917 developed a process for synthetic production of ammonia In 1930 s spent US$10M on ETM or OTEC Two land to sea steel CWPs installed offshore Cuba 1st lost during deployment, 2 nd in a hurricane

46 Claude s Work La Tunisie converted freighter deployed off Rio de Janeiro Steel cold water pipe buckled during installation

47 Offshore Brazil Anyone know where to find Claude s engineering drawings? Note safety hats!

48 CWP Design Proposal Undertake a research programme to develop an outline CWP design, including top joint, to give companies confidence it will work Use modern analysis packages (Orcaflex, Arianne, etc) to check out design

49 CWP Design Proposal Helpful if self installed & recovered pipe CWP recovered into hull for vessel dry docking/refit Design for in situ inspection, repair & maintenance

50 Scope Hopefully model test concept suitable vessel models should already exist

51 Next Stage Feedback from individuals/organizations who are interested in the concept Collaborate with organizations with complementary skills Identify best sources of funding

52 Provides Stepping Stone to Claude s Goal Helideck CWP recovery gantry Effluent discharge Warm water in Mooring line Electricity export Cold water in Fresh water expor

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