Metocean – reducing risk in Construction Projects Mark Calverley R&D manager – Fugro Metocean Business Line Society for Underwater Technology (SUT) Lunch and Learn at Charles Taylor & Co. 26th March 2015 http://www.sut.org/ 1 SUT - Lunch & Learn at Charles Taylor & Co @Fugro GEOS Ltd www.fugro.com
Outline General Introduction • Considerations • Uncertainties Planning Execution Analysis 2 SUT - Lunch & Learn at Charles Taylor & Co @Fugro GEOS Ltd www.fugro.com
Measurement Considerations Instrument Sampling Installation Measurements Choice Strategy Regional Metocean Data Metocean Data Metocean Oceanography Requirements Analysis Engineering Marine Warranty Engineering Operations Schedule / Legislation 3 SUT - Lunch & Learn at Charles Taylor & Co @Fugro GEOS Ltd www.fugro.com
Where do the uncertainties lies? Hindcast Model reliability (atmospheric, Forecast Model reliability (atmospheric, waves, currents) waves, currents) Analysis Methods Metocean Awareness Response modelling Measurement QA Metocean processes not represented in models (temporal or spatially) 4 SUT - Lunch & Learn at Charles Taylor & Co @Fugro GEOS Ltd www.fugro.com
Metocean across the phases Planning Transport / Execution Analysis Data to support operational Ways to forecast / measure Quantification of downtime, planning. Metocean conditions for Accuracy of forecasts, etc. operational planning. Ways to characterise Metocean conditions for operational planning. Forecast considerations. 5 SUT - Lunch & Learn at Charles Taylor & Co @Fugro GEOS Ltd www.fugro.com
Planning Areas of Uncertainty • Hindcast Model reliability (atmospheric, waves, currents) • Analysis Methods • Response modelling • Metocean processes not represented in models (temporal or spatially) DNV Guidance note: For meteorological and oceanographic data a minimum of three to four years of data collection is recommended. Planning generally based on hindcast data: • Temporal and spatial resolution • Validation / verification 6 SUT - Lunch & Learn at Charles Taylor & Co @Fugro GEOS Ltd www.fugro.com
Temporal Considerations What is the temporal resolution of the model data? • 1-hourly • 3-hourly • 6-hourly What are the time scales of the Metocean processes? Some processes not well represented in models include: • Squalls • Solitons • Polar lows Use of complementary data, e.g. satellite data. 7 SUT - Lunch & Learn at Charles Taylor & Co @Fugro GEOS Ltd www.fugro.com
Temporal Considerations What is the temporal resolution of the model data? • 1-hourly • 3-hourly • 6-hourly What are the time scales of the Metocean processes? Some processes not well represented in models include: • Squalls • Solitons • Polar lows Use of complementary data, e.g. satellite data. 8 SUT - Lunch & Learn at Charles Taylor & Co @Fugro GEOS Ltd www.fugro.com
Temporal Considerations What is the temporal resolution of the model data? • 1-hourly • 3-hourly • 6-hourly What are the time scales of the Metocean processes? Some processes not well represented in models include: • Squalls • Solitons • Polar lows Use of complementary data, e.g. satellite data. 9 SUT - Lunch & Learn at Charles Taylor & Co @Fugro GEOS Ltd www.fugro.com
Spatial Considerations Model resolution 10 SUT - Lunch & Learn at Charles Taylor & Co @Fugro GEOS Ltd www.fugro.com
Spatial Considerations Model resolution 11 SUT - Lunch & Learn at Charles Taylor & Co @Fugro GEOS Ltd www.fugro.com
Spatial Considerations Can the models capture the spatial scales of the Metocean processes. For example polar lows. During planning can you rely on the geographic registration of frontal features? Do the models domains extend, at appropriate resolution, to topography / coastlines that might drive the wind forcing? 12 SUT - Lunch & Learn at Charles Taylor & Co @Fugro GEOS Ltd www.fugro.com
Cost impact of choice of analysis Assume an operation west of Shetland with £250k day rate. 1. Joint frequency distribution based on 4m threshold on significant wave height. 2. Joint frequency distribution based on 4m threshold on significant wave height and peak period below 10s 3. Persistence based on significant wave height and 18 hour duration. 4. Weather windows analysis based on • 18-hour duration • Operational threshold = 4m, Tp > 10s; 2.5m, Tp < 2.5s 13 SUT - Lunch & Learn at Charles Taylor & Co @Fugro GEOS Ltd www.fugro.com
Metocean Awareness? 14 SUT - Lunch & Learn at Charles Taylor & Co @Fugro GEOS Ltd www.fugro.com
Cost / downtime with Analysis August September Analysis Hs =4m Hs=4m, Hs=4, Tp<10s Durn>18hr Downtime days August 0.45 8.2 0.10 September 3.47 18.62 4.13 Downtime cost August 112,375 2,056,452 24,800 September 868,500 4,656,458 1,031,250 Sep-Aug 756,125 2,600,006 1,006,450 WOW (hours) Weather cost (£) August September Average 1.9 8.0 20,060 83,177 Maximum 54.0 96.0 562,500 1,000,000 P10 6.0 30.0 62,500 312,500 P20 0.0 12.0 - 125,000 P30 0.0 0.0 - - 15 SUT - Lunch & Learn at Charles Taylor & Co @Fugro GEOS Ltd www.fugro.com
Planning Summary • Know your regional Metocean conditions. • Know your installation’s dependence on the Metocean conditions, what are the limiting processes. • Know your data sources. Free is good but is it fit for purpose? • Know your analysis techniques. 16 SUT - Lunch & Learn at Charles Taylor & Co @Fugro GEOS Ltd www.fugro.com
Transport Fatigue potential is high. Compare Metocean design conditions of transport to those experienced. Directly measure fatigue. Identify potential issues for inspection prior to installation. 17 SUT - Lunch & Learn at Charles Taylor & Co @Fugro GEOS Ltd www.fugro.com
Execution Forecast Reliability Measurements Response Modelling Metocean Awareness 18 SUT - Lunch & Learn at Charles Taylor & Co @Fugro GEOS Ltd www.fugro.com
Forecast (Model) Reliability Weather Forecast Meteorologist rqd. Independent WF Maximum WF Level on site source interval Yes (1) 2 (2) 12 hours (3) A No (4) 2 (5) B 12 hours C No 1 12 hours 1. There should be a dedicated meteorologist, but it may be acceptable that he/she is not physically present at site. The meteorologist opinion regarding his preferable location should be duly considered. It is anyhow mandatory that the dedicated meteorologist has continuous access to weather information from the site and that he/she is familiar with any local phenomena that may influence the weather conditions. 2. It is assumed that the dedicated meteorologist (and other involved key personnel) will consider weather information/forecasts from several (all available) sources. 3. Based on sensitivity with regards to weather conditions smaller intervals may be required. 4. Meteorologist shall be conferred if the weather situation is unstable and/or close to the defined limit. 5. The most severe weather forecast to be used. DNV-OS-H101- Marine Operations, General How is the forecast generated? 19 SUT - Lunch & Learn at Charles Taylor & Co @Fugro GEOS Ltd www.fugro.com
Are all forecasts equal? • How is the forecast generated? • Which models support the forecast? • What other ‘guidance data’ supports the forecast? • Does the forecaster have regional experience? • Are observations available to the forecaster? • Are the synoptic difficult / easy to forecast? 20 SUT - Lunch & Learn at Charles Taylor & Co @Fugro GEOS Ltd www.fugro.com
Alpha Factors WF Operation WF WF WF starts Estimated time for the operation Contingency T POP (Basis for selecting α -factor) T C T R Required weather window with OP WF = α x OP LIM α Design Hs = 2m Design Hs = 4m T POP A B C A B C ≤12 0.76 0.80 0.95 0.83 0.87 1.00 ≤24 0.73 0.77 0.84 0.80 0.84 0.87 DNV-OS-H101- Marine Operations, General ≤36 0.71 0.75 0.77 0.77 0.80 0.80 21 @Fugro GEOS Ltd www.fugro.com SUT - Lunch & Learn at Charles Taylor & Co
Alpha Factors Reliability No requirement for 2 nd forecast to be forecaster driven, many companies use model driven forecasts • to reduce cost. • Potential for underlying models to be similar, e.g. public domain models such as WW3 or ECMWF. • No consideration of ensemble forecasting • Reliability of site specific forecasts not addressed. • No consideration of reliability of models and forecasting under different synoptic conditions. • No consideration of personnel competency 22 SUT - Lunch & Learn at Charles Taylor & Co @Fugro GEOS Ltd www.fugro.com
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