MCT METOCEAN Nov17 · 2017-11-20 · NORSOK N-002, DNV-RP-C205, DNV-OS-H101 and etc. Existing Standards & Guidelines 5 •RP 2MET Purpose General requirements for developing metocean

Metocean Criteria

DR. SHU ‐HAO CHANG, P.E. AT 台灣離岸風機研討會

MCT ENGINEERING, INC.HOUSTON, TEXAS, USA

Presentation Overview METOCEAN DATA AND APPLICATIONS

EXISTING STANDARDS & GUIDELINES

INTRODUCTION TO API RP 2MET

RESPONSE-BASED DESIGN

SUMMARY

2

• Meteorological Wind (velocity, direction, profile) Atmospheric pressure Temperature Others: precipitation, humidity, fog and etc.

• Oceanographic Waves (height, period, direction, energy) Currents (velocity, direction, profile) Others: marine growth, salinity, oxygen content and etc.

Metocean Data

3

• Site selection and field development feasibility• Engineering design (construction, transportation, installation and etc.)

• Operation and maintenance• Environmental impact assessment• Model validation

Metocean Data Applications

4

• Oil and gas standards ISO 19901-1 (2005):

General requirements for the determination and use of Metocean conditions for the design, construction and operation of offshore structures of all types.

API RP 2MET (2014):Home for all API RP metocean criteria, aligned with ISO 19901-1.

OTHERS:NORSOK N-002, DNV-RP-C205, DNV-OS-H101 and etc.

Existing Standards & Guidelines

5

• RP 2MET Purpose General requirements for developing metocean criteria

‒ Determining conditions‒ Translating conditions into design parameters

Clarify terms/definitions General guidance on regional phenomena Common metocean reference for all other RPs

‒ Indicative criteria, use may be allowed without metocean study for some 2A / 2SIM / 2SK applications

Introduction to API RP 2MET

6

• Evolution of RP 2MET


7

RP 2A-WSD Section 2.3(21st Edition, 2000)

ISO 19901-1 (2005)Bulletin 2INT-MET

(May 2007)

ISO 19901-1 / RP 2MET(Nov 2014)

RP 2MET(2011-12)

• Changes from 2A, 2INT-MET to 2MET General metocean study guidelines Wave / current interaction from 2A, estimating

extreme waves and crests Interim guidance on hurricane conditions in the

GOM Wave spectra / spreading More Gulf study indicatives:

‒ Winter storms‒ Loop current / eddy‒ TRWs


8

• Comparison of API RP 2MET (ISO 19901-1) with RP 2A Sections / 2INT-MET


RP 2MET Section (ISO 19901-1) RP 2A Section / 2INT-MET1. Scope2. Normative references3. Terms and definitions4. Symbols and abbreviated terms5. Determining the relevant metocean parameters 1.3.1 General Metocean Considerations6. Water depth, tides and storm surges 1.3.4 Tides7. Wind 1.3.2 Winds8. Waves 1.3.3 Waves; local wave crest from 2INT-MET9. Currents 1.3.5 Currents10. Other environmental factors 1.3.6 IceAnnex A: Additional information and guidanceA.1 ScopeA.2 Normative ReferencesA.3 Terms and DefinitionsA.4 Symbols and AbbreviationsA.5 Determining the Relevant Metocean ParametersA.6 Water Depth, Tides and Storm SurgesA.7 Wind 2.3.2 WindA.8 Waves 2.3.1 Waves; local wave crest from 2INT-META.9 Currents 2.3.3 CurrentsA.10 Other Environmental FactorsAnnex B: Discussion of wave frequency spectraB.1 The Pierson-Moskowitz spectrumB.2 The JONSWAP spectrumB.3 Comparison of P-M and JONSWAP spectraB.4 Ochi-Hubble spectraAnnex C: Regional informationC.1 GeneralC.2 Northwest EuropeC.3 West Coast of AfricaC.4 US Gulf of Mexico 2.3.4c, 2.3.4d, 17.6.2a GOM Conditions; hurricane site-specific guidance

and indicative conditions from 2INT-METC.5 US Coast of California 2.3.4e, 2.3.4f, 17.6.2b Other US WatersC.6 Other US Waters 2.3.4e, 2.3.4fC.7 East coast of CanadaBibliography

9

• Core Document – Key SectionsIntroduction to API RP 2MET

RP 2MET Section (ISO 19901-1)1. Scope2. Normative references3. Terms and definitions4. Symbols and abbreviated terms5. Determining the relevant metocean parameters6. Water depth, tides and storm surges7. Wind8. Waves9. Currents10. Other environmental factors

Extreme (10-2 / year) & abnormal (10-3~10-4 / year)Long-term distributionsNormal environmental conditions

Water depth: reference datum of water depth (e.g. MSL);Wind: mean and the standard deviation of speed (order of an hour), mean direction,

wind profile (10m above MSL as a reference);Waves: height, crest elevation , period and direction

wave energy spectra / surface elevation (t) for structural dynamic responsesea state (assumed to be 3 hours but depends);

Currents: total velocity, profile, blockage;Others: marine growth (may increase mass, dimension and Cd)

tsunamis, seiches, sea ice, snow and etc. 10


RP 2MET Section (ISO 19901-1)Annex A: Additional information and guidanceA.1 ScopeA.2 Normative ReferencesA.3 Terms and DefinitionsA.4 Symbols and AbbreviationsA.5 Determining the Relevant Metocean ParametersA.6 Water Depth, Tides and Storm SurgesA.7 WindA.8 WavesA.9 CurrentsA.10 Other Environmental FactorsAnnex B: Discussion of wave frequency spectraB.1 The Pierson-Moskowitz spectrumB.2 The JONSWAP spectrumB.3 Comparison of P-M and JONSWAP spectraB.4 Ochi-Hubble spectra

Annex A: more guidance on core topics

Appendix B: wave spectra formulas

11


RP 2MET Section (ISO 19901-1)Annex C: Regional informationC.1 GeneralC.2 Northwest EuropeC.3 West Coast of AfricaC.4 US Gulf of MexicoC.5 US Coast of CaliforniaC.6 Other US WatersC.7 East coast of Canada

Appendix C: regional information for various parts of the world, of different detail / quality

Houston

12

C.4: US Gulf of Mexico

• Extreme metocean parameters ( US GOM) Hurricanes; Winter storms; Loop current and loop current eddies (LCE); Combined loop current and storm events; Topographic Rossby waves (TRWs); Air and sea temperatures.


13

• Hurricane Guidance Guidance:

‒ Use 50-100 year data set, including through 2008

‒ Site pooling or averaging to account for track shift

‒ Use synthetic/deductive for long return periods

Indicative:‒ Three areas for “annual” conditions

‒ Central most severe


14Figure C.13 - Full Population Hurricane Areas of the Gulf

• “Sudden” Hurricane GuidanceGuidance:

‒ Develop using “watch circle” approach, time of arrival of storm conditions appropriate to operation considered

Indicative:‒ One set for GOM, representative of those storms bringing tropical storm-

force winds to sites north of 28 o N 24 hours after storm formation


15

• Seasonal Hurricane GuidanceGuidance:

‒ Can evaluate hazard as pre- and

post-peak periods

‒ Should not base on single months

‒ Consider other hazards (winter storm)

outside of hurricane peak

Indicative:‒ Two sets provided, West/Central and East, deepwater areas

‒ Early (May-July) and Late (October-November) season periods


16

• Winter Storm GuidanceGuidance:

‒ Important for operations, especially October-March

‒ Use measurements (NDBC buoys), hindcasts as appropriate

‒ Include 1980’s

‒ Highest observed ~ 9 m Hs

Indicative:‒ One set of conditions for deepwater


17

Infrared satellite images of the “Storm of the Century” (March 13, 1993) .Image credit: CIMMS Satellite Blog

• Loop Current GuidanceGuidance:

‒ Govern mooring design for some facilities, and riser/tendon design

‒ Use historical record through 2008, caution with pre-1985 years

‒ Site pooling and averaging

‒ Consider joint Loop-hurricane occurrence

Indicative:‒ Maximum surface current case

‒ Provided for 10- and 100-year


18

Figure C.29 — 10-year loop current/eddy surface speeds (m/s)

Figure C.30 — 100-year loop current/eddy surface speeds (m/s)

• Topographic Rossby Wave Guidance Guidance:

‒ TRW condition important for risers and drilling operations along Sigsbee Escarpment

‒ Ability to model evolving, recommend 1-2 years of measurements at site

‒ May be correlated to Loop proximity

Indicative:‒ 10- and 100-year conditions provided


19https://ars.els-cdn.com/content/image/1-s2.0-S0967064510001712-gr1.jpg

• Operational Operational Hs-Tp

‒ Data from NDBC 42001

‒ Set does not represent extreme events

Wind roses for June, December‒ From 42001

Sea, air temperature ranges‒ From industry, NDBC measurements


20Figure 31 — June/December wind roses — Northwest Gulf of Mexicohttp://www.ndbc.noaa.gov/images/stations/scoop.jpg

• US Gulf Annex Summary Site-specific criteria is always preferred – annex values do not

override a proper site-specific study

Select Gulf annex values may be used with 2A and 2SIM for depths less than 120 m, as mapped from L- and A- to appropriate return periods

May be used with 2SK for low consequence operations


21

• Metocean conditions for structural designResponse-Based Analysis

StructuralModel

WindWaveCurrentDirectionality

Operational: 1-yearExtreme: 100-year (10-2)Abnormal: 1000- ~ 10000-year(10-3 ~ 10-4)

WindWaveCurrentDirectionality

WindWaveCurrentDirectionality!

Fixed jacket

Floating system

Extreme: 100-year (10-2)Abnormal: 1000- ~ 10000-year(10-3 ~ 10-4)

Extreme: 100-year (10-2)Abnormal: 1000- ~ 10000-year(10-3 ~ 10-4)

22

• Metocean conditions for structural design Independent extremes (guideline)− API: extreme independent with associated conditions (API)

Response based conditions− Based on extreme response

− Long-term environmental dataset (30 years)

− Jacket model

Response-Based Analysis

Table C.28 — Factors for combining independent extremes into load cases in shallow water(10 m ≤ depth ≤ 50 m) 23

• Response of offshore structuresResponse-Based Analysis

https://wonderopolis.org/wp-content/uploads/2014/07/dreamstime_xl_22656707-custom.jpg

Metocean Environment

https://i.pinimg.com/originals/f4/cf/32/f4cf32dc2b9c6b9df8aa89cf4910283e.jpg

Offshore Structures

Response Based Metocean Design

ConditionsResponses

Extreme Value Analysis on Responses

Operatingbehavior Design Cases for

N-year responseN-year values for responses

Jobs for metocean specialists

24

• General procedure of RBA Response-Based Analysis

(1)• Develop a long-term metocean database

(2)• Use peak-over-threshold method to identify independent storm

(3)• Select sea states from identified storm that may cause critical response

(4)• Generate short-term responses for selected sea states

(5)• Choose the most critical response and associated sea state from each

storm event (multiple sea states)

(6)• Rank the selected peak responses of all storms and calculate their

probabilities

(7)• Fit peak response and probability and calculate the design response for

the N-year return period

(8)• Estimate the design environmental conditions likely to produce the

responses of a chosen N-year return period

(9)• Estimate the safety (load) factors required to ensure target reliability

25

• General procedure of RBA (cont.)Response-Based Analysis

(1) • Develop a long-term metocean database

(2)• Use peak-over-threshold method to identify independent storm






probabilities






26

• requires a long-term database of:Waves− wave height, period and direction or− directional wave spectrum or− wind-sea and swell

Winds− Speed and direction− Wind spectrum− Wind profile

Currents− current speed and direction− current profile


27

• General procedure of RBA (cont.)•



(2)• Use peak-over-threshold (POT) method to identify

independent storm






probabilities






28

• Peak-over-threshold (POT) filteringResponse-Based Analysis

Picture source from Shell Exploration and Production 29




(2)• Use peak-over-threshold (POT) method to identify independent storm

(3)• Select sea states from identified storm that may cause

critical responses





probabilities






30

• Selected sea states from a stormResponse-Based Analysis

31





(3)• Select sea states from identified storm that may cause critical

responses

(4) • Generate short-term responses for selected sea states




probabilities






32

• Short-term responseResponse-Based Analysis

33

• Long-term extreme response analysis methodResponse-Based Analysis

(Tromans and Vanderschuren, 1995)

34

• Effect of short-term variabilityResponse-Based Analysis

(Forristal, Larrabee and Mercier, 1991)35






responses


(5)• Choose the most critical response and associated sea

state from each storm event (multiple sea states)


probabilities






36

• Critical responses of fixed platform Displacement Shear force Bending moment


37






responses




(6)• Rank the selected peak responses of all storms and

calculate their probabilities






38

• Calculate the probabilities of selected sea statesResponse-Based Analysis

39






responses





probabilities

(7)• Fit peak response and probability and calculate the

design response for the N-year return period




40

• Fit peak response and probabilityResponse-Based Analysis

41






responses





probabilities



(8)• Estimate the design environmental conditions likely to

produce the responses of a chosen N-year return period


42

• N-year return periodResponse-Based Analysis

Hmps_100

Q(Hmps|n-years)

Q(Hmps|100-years)

43






responses





probabilities





(9)• Estimate the safety (load) factors required to ensure

target reliability 44

• Response of offshore structuresResponse-Based Analysis

https://wonderopolis.org/wp-content/uploads/2014/07/dreamstime_xl_22656707-custom.jpg

Metocean Environment

https://i.pinimg.com/originals/f4/cf/32/f4cf32dc2b9c6b9df8aa89cf4910283e.jpg

Offshore Structures

Response Based Metocean Design

ConditionsResponses

Extreme Value Analysis on Responses

Operatingbehavior Design Cases for

N-year responseN-year values for responsesJobs for

offshore structural engineer 45

• Design Cases for N-year responseJacket In-place Structural Analysis

100-year Extreme Storm wave, wind and current 5-year Operating Storm wave, wind and current

46

Thank you!

Questions?

Photo source from http://dudgeonoffshorewind.co.uknewsnewsimagesnews02-06-16-jacket-sail-away.jpg

47

MCT METOCEAN Nov17 · 2017-11-20 · NORSOK N-002, DNV-RP-C205, DNV-OS-H101 and etc. Existing Standards & Guidelines 5 •RP 2MET Purpose General requirements for developing metocean

Documents