New Innovative Anchor Solution for Deepwater Mooring Gravity Intalled Anchors Reduce Time and Costs of Marine Operations Jon Tore Lieng CTO

Transcription

1 New Innovative Anchor Solution for Deepwater Mooring Gravity Intalled Anchors Reduce Time and Costs of Marine Operations Jon Tore Lieng CTO Wokshop on Deepwater Subsea TieBack Damai Puri Resort & Spa, Kuching, Sarawak, Malaysia 24th26th January 2011

2 Technology developer and provider of innovative anchor solutions for floating structures Expertise in marine soil mechanics Located in Trondheim, Norway

3 Available Anchor Types

4 Anchor Types drag embedment VLA DENNLA Bruce Anchors STEVMANTA Vryhof

5 Anchor Types cont. Pump skid Suction anchor SEPLA Suction Embedded Plate Anchor D = 56.5m L = 2030m W dry = tons Soft sediments m

6 Pump skid Seabed Installation of Suction Anchors 1 Positioning Monitoring of verticality heading clearance Total time at seabed: 3 9 hours depending on anchor dimensions and sediments. 2 Monitoring of verticality diff. pressure penetration Evacuation of entrapped water 3 Recovery of pump skid lifting wire

7 Long Piles Hydraulic Pile hammer D = 23m L = 4060m W dry = tons Soft sediments

8 Criteria for Needed Deep Water Anchor as defined by Deepwater Technology program Norwegian Research Council 1995 Anchor installation must be simple and cost effective The anchor must not be complicated or too expensive to fabricate Allow for taut leg mooring

9 Deep Penetrating Anchor DPA Theoretical design

10 Deep Penetrating Anchor DPA Dry weight: tons Typical inclined capacities: 650 to 1450 tons 1218m Theoretical design

11 A Real Torpedo

12 Principles of Anchor Concept: Optimum fluid dynamic design to achieve high velocity and deep penetration. Huge kinetic energy derived through freefall no external energy source required. Soil remolding during penetration large friction resistance after consolidation

13 Installation may be installed with one vessel

14 Deep Penetrating Anchors for floating structures: FPSOs/FPSs SPARs Riser Buoys MODUs Offshore Energy Power Units Geographical areas of use: All areas where soft sea bed conditions are found No depth limitations

15 Keynote paper OTC (2004): Torpedo/DPA anchors appear to be the most promising option for improvement in cost reduction and simplifying installation. Technology Assessment of Deepwater Anchors Clarence J. Ehlers, et al. Sr. Facilities Engineer ChevronTexaco/Exploration & Production Technology Co. DPS/Floating Systems Unit/Anchors, Moorings & Risers Team

16 Suitable Geographical Areas

17 Technological Development Extensive theoretical research CFD & geotechnical Economical evaluation cost comparison with other solutions Small (1:25) lab and large (1:3) scale testing Troll Field Fullscale pilot at the Gjøa Field leading to a qualified anchor in Q4 2009

18 Anchor velocity, (m/sec): Anchor velocity vs travelled distance Anchor Velocity vs Drop Height 75ton DPA Terminal velocity: 37m/sec Assumed velocity 25m/sec at seabed (70% of terminal velocity) Drop height: minimum 50m Drop height, (m): No drag resistance Viscos drag on anchor & chain

19 Drop distance, (m): Hydrodynamic Stability monitored test Anchor Tilt, (dgr): sensor disturba 35 Final tilt ~ 1 dgr.

20 GJØA Full Scale Pilot & Qualification

21 Installation of two 80t DPA s at the Gjøa Field in the North Sea

22 Fabrication

23 Fabrication Nose

24 DPA s Ready for Transport to the North Sea

25 80t DPA as installed at the Gjøa Field Flukes 4m x 6m steel plates Characteristic capacity ~ 800t 13m 1.2m diam. shank Massive tip

26 Gjøa field layout NB! Not to scale. Satellite F Typical Mooring Scheme All Templates at orientation Template E NW N Template D NE Template C Gjøa Semi Template B Riser area location SW Anchor clusters SE

27 DPA Locations at Gjøa DPAs 1.5kM apart Template E DPA 1 Stiffer soil Template BCD Softer soil DPA 2 DPAs to be used for both Template sites

28 Loading Direction Limited loading direction Omnidirectional loading ±5 o

29 Installation Vessel Island Vanguard

30 Two DPA s on Deck

31 DPAs on Deck of Island Vanguard

32 Container for instrumentation

33 Markings on Chain and Retrieval Wire for Instrumentation

34 To stern roller Release point Anchor Drop Configuration Trailing chain length Permanent mooring line Loop height Drop height 5075m Instrumentation Installed anchor

35 As Installed DPAs at Gjøa DPA 1 (North) Stiffer soil seabed DPA 2 (South) Softer soil < 2 o 21m < 2 o estimated actual 24m 27.5m estimated 30m actual Accuracy in horizontal plane: ± 1.5m

36 Qualified Technolgy within Statoil

37 Available AHTS for Efficient Installation

38 Why DPA? Installation time and costs Standard Anchor Handling Vessel (AHTS) No external energy source required Precise horizontal positioning

39 Why DPA? Cont. Independent of water depth No proof loading required High utilization of deck storage area More cost effective