WP4 INITIAL CONSIDERATIONS REGARDING FUNCTIONAL REQUIREMENTS

1. WP4 INITIAL CONSIDERATIONS REGARDING FUNCTIONAL REQUIREMENTS

2. WP4 structure & Progress • Tasks: • Define Worst Case Scenario • Formulate initial analysis model • Define & agree of functional specifications • Issue detailed workplan • Define functional specs values • Write Deliverables DIFIS PROJECT-WP4

3. INITIAL MODELS DIFIS PROJECT-WP4

4. Simplified Riser Flow Models I • The pipe is solid • The density of oil is smaller than the density of water • The dynamic viscosity of oil is very high. • The surface tension is neglected • The oil spill is considered as a solid cylinder • The flow is continuous ρw water density ρoiloil density R radius of equivalent sphere Re Reynolds number of the flow Ψ orbicularity CD drag coefficient • In order to perform flow calculations for a cylinder with dimensions d, H, is considered as a sphere, with it’s drag coefficient CD, is varied by the Reynolds number (Re) and orbicularity • Orbicularity: The external area of a sphere which has the same volume with the cylinder DIFIS PROJECT-WP4

5. Simplified Riser Flow Models II • The pipe is solid • The density of oil is smaller than the density of water • The dynamic viscosity of oil is very high. • The surface tension is neglected • The oil spill is considered as a solid cylinder • The flow is continuous New variables introduced λfcoefficient of frictiongiven by a Moody diagram DIFIS PROJECT-WP4

6. Parametric Study • As expected : • A larger riser diameter results into higher rising velocities • Lower density oil will have higher rising velocity DIFIS PROJECT-WP4

7. Mass flow rates for model I The diameter of the rising oil column was kept that small for reasons of protecting the flow from contact with the riser walls. Appropriate design can allow for larger diameters DIFIS PROJECT-WP4

8. Comments on the models • Model I represents an upper limit, while model II a lower limit • These models do not take into account the deformation of the riser due to wave forces • The separation of the oil spill by a water column inside the riser tube will be advantageous in the rising velocity. This leads to the following (possible) design requirements • Control of leaks by introducing/sealing holes with an ROV • Adoption of a high diameter riser tube • Introduction of densities as functions of depth and temperature • Introduction of surface tension • Consideration of one liquid (2-phase flow) • Bent riser flow model DIFIS PROJECT-WP4

9. Anchoring model (by Peter Davies et al-IFR) • 100 tons buoyancy : 1400 m lateral displacement (50 tons /anchor) • 1000 tons buoyancy: 320 m lateral displacement (high anchoring loads) Deformable Model Results DIFIS PROJECT-WP4

10. DIFIS Dimensioning procedure Initial considerations • The whole wreck’s length must be covered by the inverted funnel. • The funnel must not come in contact with the vessel ULCC dimensions DIFIS PROJECT-WP4

11. DIFIS Dimensioning From trigonometric relationships DIFIS PROJECT-WP4

12. Other Scenarios taken into account In order to achieve a first estimation of a minimum value for angle θ, the dome’s baseline length and the ship are assumed to have the same horizontal length l. DIFIS PROJECT-WP4

13. DIFIS Procedures I(Pre intervention) • Contact with competent local authorities for intervention approval-coordination • Contact with ship-owner for acquisition of vessel’s schematics and cargo data (if available • Contact with ROV operators for ROV leasing • Contact with DIFIS logistics system for acquisition/preparation of raw materials/buffer bell • Definition of exact wreck position • Funds Acquisition (call for tender, use of emergency budget contact with cargo/vessel owner) DIFIS OPERATOR • Deployment of sensor arrays for ROV positioning • Sea-bed Mapping • Sea-bed Soil sample acquisition • Oil sample Acquisition • Wreck Monitoring ROV OPERATOR DIFIS PROJECT-WP4

14. DIFIS Deployment Procedures II(Pre intervention) • Initial dimensioning process-Initial models • Anchoring analysis – Contact with anchoring operator for design and availability of anchoring system • Risk-benefit analysis • Initial cost estimate analysis- Funds acquisition • Transport of data to anchoring operator-coordination of anchoring design • Acquisition of access to vessels required for DIFIS deployment DIFIS Operator • ROV operating vessel • DIFIS deployment vessel(s) • Tanker vessels availability DIFIS PROJECT-WP4

15. DIFIS Intervention/Sustenance Intervention • Arrival of Vessels on site • Deployment of Anchoring system • DIFIS Deployment • Initial inspection/ implementation of the monitoring system Sustenance • Tanker vessels for transport of oil • DIFIS status monitoring • Possible repair/maintenance procedures • Procedures for removal of DIFIS • Post inspection of reusable components DIFIS PROJECT-WP4

16. Design Considerations Anchoring • VLAs or DEAs are more prominent as anchoring systems (low cost, easily retrievable) Dome- Riser Construction • Initial Study by Ifremer pointed out that high buoyancy is required to keep the buffer bell under low lateral displacements. • High strength materials must be used for the whole setup Reinforcement rings must be used to protect keep the riser-dome interface shape circular • The same solution should be considered for the riser • Maybe two or three DIFIS along a ULCC should be considered DIFIS PROJECT-WP4

17. Design Considerations II • Buffer Bell Material Choise • Steel buffer is cheaper than a GFRP one • GFRP buffer bell allows for : • Higher reusability • Lower weight on deployment • Lower need for monitoring of corrosion. Post deployment inspection • Both technologies well-proven in marine constructions Caution points on Mooring Lines • UV protection near surface • Foreign Object Damage protection near the seabed DIFIS PROJECT-WP4

18. Worst case scenario definition • Tanker : VLCC = 300000 tons of cargo, 415 m length • Geographical Location : AREA 1 (max depth 4000 m) • Weather Conditions (Month :February) • Cargo: High density crude or refined oil Average Wave Height Average Wave Period DIFIS PROJECT-WP4

19. Proposal for deployment • The anchors are installed by the anchor operator in positions determined by the anchoring study preceding deployment • The whole DIFIS setup is assembled on board, with the riser and dome being folded. • The folded DIFIS system is lowered into the water, with suitable ballast so that two provisions are satisfied: • The buoyancy of the buffer bell and the whole system is nullified • The velocity achieved due to the ballast must be such that it will allow for already deployed ROVs to make small adjustments during vertical motion towards the sea-floor • The DIFIS mooring lines are secured on anchoring points by the ROVs • Ballast is removed and the riser commences unfolding due to the buoyancy of the buffer bell. Buffer bell depth is controlled by mooring lines’ length and tension due to buoyancy • ROVs unfold the dome and secure it in designed dimensions DIFIS PROJECT-WP4

20. DIFIS Retrieval • Pyrotechnic cutters cut the mooring lines, near anchoring points. (the buoyancy forces are high and such a work could prove dangerous for an ROV) • The buffer bell surfaces along with the dome and riser and is retrieved by surface vessels • The anchors are removed by the anchor operator DIFIS PROJECT-WP4

21. General functional specifications • Minimum & Maximum operational depth (4000m) • Minimum & Maximum oil properties (NOAA database minimums & Maximums) • Time to intervention (as soon as feasible) • Operational environmental conditions • Deployment environmental conditions • Cost of intervention DIFIS PROJECT-WP4

22. Sub-systems of the DIFIS setup 1 2 3 4 DIFIS PROJECT-WP4

23. 1.Buffer Bell • Inherent Buoyancy (to be determined) • Construction Material (steel or GRP) • Strength of Anchoring Points (determined by anchoring calculations) • Operational Depth (initial idea from proposal Part B: 30~50m) • Shuttle Tanker Interface (Submerged buoy-bearing to allow for weathervaning) • Ballast & Stability system (determined by buoyancy) • Maximum Capacity • initial idea: (Part B): 1600 m3 (oil density 950 kgr/ m3)= 14630 tons => 20 trips to unload the oil for a VLCC • Lifetime: REUSABLE • DAQ & misc electronics for monitoring system DIFIS PROJECT-WP4

24. 2&3Riser tube and Funnel RISER • Construction Material • Diameter (~2m, dependant of oil flow calculation limits) • Length: Dependent of wreck depth • LIFETIME: Preferably REUSABLE FUNNEL • Construction Material • Dimensions • Operational Depth (see initial calculations) • LIFETIME: Preferably REUSABLE DIFIS PROJECT-WP4

25. 4. Anchoring system Anchors • Type (VLA/DEA) • Maximum pullout force • Anchorage deployment requirements (env. conditions by ALV) • Geotechnical Applicability (dependant of accident site) • Installation time • LIFETIME: REUSABLE/LEASED Mooring Lines • Material • Dimensions • Strength (static and fatigue) • Number • LIFETIME: Dependant of Anchoring operator specs DIFIS PROJECT-WP4

26. Support Systems Oil Recuperation Tanker • Weather conditions (2-3 knots currents) • Capacity (one buffer bell= 14630 tons) • Mooring system (turret mooring, either internal/external) • Cost of leasing • Availability • Specifications (depth speed sensors) (WP3 SoTA) • Type • Manipulation Procedures Required & Equipment • Deployment conditions • Time of Use • Cost ROVs DIFIS PROJECT-WP4