Site Investigations for Offshore Wind

Transcription

1 Site Investigations for Offshore Wind A multi-disciplinary approach Mattijs de Lange Gardline Marine Sciences Limited My thanks to: Maarten Timmerman David Cerda Saltzman Sue Crothers Albert van der Hem Cliff Whatrup 1

2 Choose a Location Consents and Permitting considerations 2

3 Design your layout Turbine locations will be defined by: Wind directions/yield Water Depth Geology Shipping Lanes Access to Shore Bird Migration Paths Etc. Turbine Design considerations rotor hub nacelle RNA blade tower platform ladder boat landing transition piece support structure offshore wind turbine power J-tube scour protection mudline cable scour hole foundation pile 3

4 Forces on Foundations air wind waves & current sea soil Preliminary Site Assessment Review existing data and undertake a desk study. Consider Pre-Existing Geological data and key geological processes Preliminary met ocean conditions Identify geotechnical risks Identify areas of insufficient information Outline scope of survey 4

5 Preliminary Site Assessment Preliminary Site Assessment 5

6 Preliminary Site Assessment Preliminary Site Assessment 6

7 A Cautionary Note No recognised guidelines on survey practice for wind farms similar to those outlined for oil and gas by UKOOA An up to date replacement for SUT s OSIG 2005 guidance notes on Site Investigation for Offshore Renewable Energy Projects not yet published Client knowledge based upon previous experience in the design of offshore wind-farms has been very limited due to inexperience and lack of engagement with Oil & Gas sector. There is always a need to minimise survey costs. Funding to do a proper job of the survey only approved after completion of a formal acceptance of an Environmental Impact Assessment. but survey work is required for a comprehensive EIA archaeology, UXO and habitat assessments Site Investigations Need to ensure full swathe bathymetry t and sonar coverage over survey area Ensure sub-bottom profiler data below all probable turbine locations (piling locations), to anticipated pile depth Probable need to see below the multiple in shallow water, and map the refusal surface for foundation design. (Consider the use of multi-channel techniques) Detailed shallow penetration geophysics for cable routes and jack-up leg penetration Different tasks have different requirements: 7

8 Consider what you need from your data and / or Survey Scope Phase 1 - Geophysics Decide on the need for a reconnaissance or detailed IHO Order 1survey over the whole site Establish bathymetry using swathe systems Indentify and locate seabed hazards Determine geometry of subsurface layers Develop your scope for detailed survey or subsequent geotechnical investigations 8

9 The Right Survey Vessels The Right Equipment 9

10 The Right People Bathymetry 10

11 Sea Bed Features Sub-bottom Geology 11

12 Survey Scope Phase 2 - Geotechnics Thickness and properties of seabed layers Complexity of the geological model Presence and distribution of hazardous layers Variability and uncertainty in geotechnical parameters Number of CPT tests vs. Number of Boreholes The Right Drill Vessels 12

13 The Right Equipment The Right People 13

14 Geotechnical Surveys Provide Refined geological model Variation in ground conditions Idealised ground profile at foundation location Geotechnical parameters for foundation design Identification of geotechnical hazards Geotechnical Survey Results 14

15 Geotechnical Survey Results Refined Geological Model 15

16 Parameters for Foundation Design Metocean Data 16

17 Metocean Data Data Integration and Reporting Data comparison over time 17

18 Data Integration and Reporting Wind turbine suitability mapping: Data Integration and Reporting 3D visualisation example with data from different sources: 18

19 Foundation Design Length Diameter scour protection mudline scour hole Foundation Design 19

20 Foundation Design Questions Mattijs de Lange Gardline Marine Sciences Limited 20