June 2014 © Slide #1 McNeilan & Associates
DOE-DOI Offshore Wind
Workshop
Geophysical and Geotechnical Considerationsfor U.S. Offshore Wind Development
Workshop on Offshore Wind EnergyStandards and GuidelinesArlington, VA – June 2014
Tom McNeilan, McNeilan & Associates [email protected]
June 2014 © Slide #2 McNeilan & Associates
DOE-DOI Offshore Wind
WorkshopG&G Program Requirements & Uses
Required for:• Geologic hazards evaluations and definition of site suitability & risks• Engineering design (foundation type selection, foundation design,
cable routing and design)• Regulatory permitting (to obtain approvals of COP and FIP permits)• Predicting foundation & foundation installation costs (and schedule)• Defining installation requirements• Understanding & managing project riskLinkages to other siting studies• Environmental• Archaeological• Met-Ocean (wind, wave, current, and ice loads and hazards)Separate or Integrated?• Tasks• Through project lifetime
Integration allows 1 + 1 + 1 + 1 = 8
Different entities (owner, engineer, BOEM, etc.) place different priorities on these
different requirements
June 2014 © Slide #3 McNeilan & Associates
DOE-DOI Offshore Wind
WorkshopEuropean Experience
What are the lessons to be learned from OW in Europe?• Many early projects (in the early/mid 2000s) suffered from poor quality,
incomplete, or untimely AOS data Poor or inappropriate designs Couldn’t be installed with planned equipment Created delays (with associated cost increases) Optimum wind turbines not matched to local conditions Produced energy less than & more expensive than expected
• Significant improvements as industry matured, but …….• Crown Estate’s Offshore Wind Cost Pathway Studies continues to
advocate more investment for quality data earlier Suggest increasing pre-financial close investment by 5% for
earlier & more complete G&G studies can save up to 10 % to 20% of project capital cost
June 2014 © Slide #4 McNeilan & Associates
DOE-DOI Offshore Wind
Workshop
Northern Europe OW Industry+ open ocean experience+ offshore wind experience– lack of BOEM experience– not local
East Coast Marine Industry– waterfront, not open ocean– no offshore wind experience– no BOEM experience+ local
Gulf of Mexico O&G Industry+ open ocean experience– no offshore wind experience+ BOEM experience– not local
Conclusion:Experience from all 3
sides of triangle must be merged and integrated
Sources of Applicable Expertise
June 2014 © Slide #5 McNeilan & Associates
DOE-DOI Offshore Wind
WorkshopBOEM – GGARCH Guidelines
BOEM’s GGARCH Guidelines for Geophysical, Geotechnical & Archaeological Surveys• Derived from U.S. O&G and other offshore wind experience,
Guidelines & Standards
• Note what is missing – typical East Coast waterfront “marine” practices and methods
• Current November 2012 version due to be updated
June 2014 © Slide #6 McNeilan & Associates
DOE-DOI Offshore Wind
WorkshopBOEM – GGARCH Guidelines
BOEM’s GGARCH Guidelines for Geophysical, Geotechnical & Archaeological Surveys• Current version includes different approaches for different elements of
minimum expectations for G&G (& Arch) activities
• Guideline minimums are often are viewed as being “this is what is required.”
Guideline Element 100% Prescriptive
100% Performance
basedArchaeological Requirements Geophysical DataGeological Interp & ReportGeotechnical Data & ReportEngineering Analyses & Report
June 2014 © Slide #7 McNeilan & Associates
DOE-DOI Offshore Wind
WorkshopKey Considerations
Key Geological and Foundation Considerations• Seafloor Irregularity, Sediment Mobility & Scour
• Subsurface Variability & Channeling
• Dynamic Response of Turbine – Tower – Foundation System• Foundation Installation Uncertainties Much of Offshore Wind Project
Risks Lies in the Ground
June 2014 © Slide #8 McNeilan & Associates
DOE-DOI Offshore Wind
WorkshopGeophysical Surveys
What is required for a high quality & successful survey?• Suitable Vessel with appropriate line keeping and
Adequate berthing Adequate deck space and deployment systems Area for data collection, QA/QC, and archiving Acoustically quiet
• Appropriate systems Multi-beam bathymetry Side scan sonar and magnetometer Chirp sub-bottom profiler Mid-penetration seismic reflection system –
Sound source & Hydrophone (array)• Appropriate deployment geometry and operational sequencing• Skilled and experienced operators and data processers• Appropriate safety and marine mammal avoidance procedures
Systems geometry and firing timing are
underappreciated keys to high quality data
June 2014 © Slide #9 McNeilan & Associates
DOE-DOI Offshore Wind
WorkshopGeophysical Surveys
What are the most important geophysical data? Difference between “commodity data” & “value added data”
• MBES – Seafloor conditions & morphology. Sediment mobility.• SSS & Magnetometer – seafloor conditions, artifacts and target.• Chirp & Mid-penetration Seismic Reflection (boomer) – Sub-surface
geology and stratigraphy. Extrapolation between Borings.
System Relative Complexity Relative Value Relative Cost
MBES BathymetrySide Scan SonarMagnetometerChirp Sub-bottomMid-Pen Boomer
June 2014 © Slide #10 McNeilan & Associates
DOE-DOI Offshore Wind
Workshop
MBES Quality is determined by;• System Choice & Beam Pattern• Water Depth• Vessel Speed
Multi-beam Data Quality
June 2014 © Slide #11 McNeilan & Associates
DOE-DOI Offshore Wind
Workshop
MBES Data for Sediment Mobility• Fishermens Energy – NJ State Lands Project –
Comparison of Pre- and Post-Sandy Bathymetry
Multi-beam Data Examples
Pre- & post-Sandy data acquired by Alpine Ocean Seismic Survey under contract to Fishermens Energy
2011 profile across ridgePost-Sandy profile across the ridgePost-Sandy hydrographic contoursColors show bathymetric change
Legend for bathymetric change colors –—>
June 2014 © Slide #12 McNeilan & Associates
DOE-DOI Offshore Wind
Workshop
MBES Data for Sediment Mobility• Virginia WEA – Comparison between 2013 regional survey lines and
2011 full-coverage NOAA mapping
`
Multi-beam Data Examples
2013 data acquired by Fugro under contract to Virginia DMME and BOEM
2011 NOAA full-coverage data, bathymetry rendering
2013 MBES swath width showing elevation change
Color palette for elevation change shownat right:
June 2014 © Slide #13 McNeilan & Associates
DOE-DOI Offshore Wind
Workshop
Seismic Reflection Data Acquisition Process4.5m
Navigation
Antenna
CRP
24-Channel Hydrophone
Tail Buoy
(1.56 m Group Interval)
Single-Plate Boomer
SHORT ARRAY STREAMER
Tow Depth – 0.3 m
12.0 m6.25 m35.9 m
WATER
DENSE SAND
SOFT CLAY
“Boomer” seismic energy source “fires” ~ every 5 feet along vessel trackline Energy passes through water column and some reflects off seafloor and is recorded by hydrophonesOther energy passes reflects off deeper layers & is recorded by hydrophonesThese “reflections” appear as “reflectors” on the seismic data
Wavelet- +
American Polarity
Seismic Reflection Data Acquisition
June 2014 © Slide #14 McNeilan & Associates
DOE-DOI Offshore Wind
Workshop
Subsurface with “nested” paleochannelsNegative amplitude reflection
Slide 2
Positive amplitude reflections
Seismic Reflection Example
June 2014 © Slide #15 McNeilan & Associates
DOE-DOI Offshore Wind
Workshop
Geophysical Seismic Reflection Data Comparison • Comparison of typical single-plate, single-channel boomer data (left) &
multi-plate, multi-channel boomer data (right)
Minimum imaging depth required by BOEM
Seismic Reflection Data Examples
Vertical & horizontal scales of records are adjusted to be equalAqua arrows point to common locationYellow arrows point to water bottom multiplesTan arrowed bar shows depth of usable dataData are from Mid Atlantic OCS
Both are “boomer” data? how to specify what is required ?
June 2014 © Slide #16 McNeilan & Associates
DOE-DOI Offshore Wind
Workshop
Geotechnical Drilling Vessels and Platforms• Jack-up – suitable to possibly ~18m water depth• Four-point anchor vessel with center-well• Land drilling rig on barge (for comparison)
Photos are at approximately equal scale
Geotechnical Exploration
June 2014 © Slide #17 McNeilan & Associates
DOE-DOI Offshore Wind
Workshop
Geotechnical Sampling & Testing • In situ testing (left) & on-board lab testing (right) is standard procedure
• Down-hole systems(above) andtethered seafloorsystems (right)
Geotechnical Exploration
June 2014 © Slide #18 McNeilan & Associates
DOE-DOI Offshore Wind
Workshop
Geotechnical In Situ Testing• In Situ Testing is not explicitly required by
GGARCH, but is standard of practice in Europe
Geotechnical Exploration
I would rather have 60 CPTs and 10 borings
than a ~ equal cost 20 to 25 borings only
June 2014 © Slide #19 McNeilan & Associates
DOE-DOI Offshore Wind
Workshop
Interpretation Expectations• Maps and cross-sections that display conditions
& their variability to manage subsurface risks anddefine engineering properties & their variations
Integrated Interpretation
Virginia WEA Subsurface feature Map prepared by Fugro under contract to Virginia DMME and BOEM
June 2014 © Slide #20 McNeilan & Associates
DOE-DOI Offshore Wind
WorkshopEpilogue
Or as said in Europe ….all projects pay for a quality G&G program ̶
whether one is conducted …. or not
Data RiskUncertainty Cost
Increased knowledgereduces uncertainty toreduce cost and risk
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