Metocean Committee 2002-4 activities

Chris Shaw

Chairman OGP Metocean Committee

Shell International E&P

Metocean Committee

Application of (new) metocean technology in the (offshore) oil and gas industry

Balance economic benefits with appropriate safety margins

Develop standards and guidelines

Meets twice/year, in Europe and USA

WASP (West Africa Swell Project)

Current turbulence measurement GOM

Squall measurement & analysis programme

Safety guidelines for metocean surveys

New version OWP Weather Forecasting

Handbook

Programmed satellites for metocean data

collection

Metocean Committee2002-4 activities

• Better discrimination of low frequency end of wave spectrum is one of most pressing problems for design and analysis of floating systems

• Floating systems very sensitive to peak periods and the shape of the spectrum

• West Africa is particularly important area

West Africa Swell Project (WASP)

Development of a Swell Event offshore Nigeria

19 July 1998

Frequency

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Distance to storm = 9000 km

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Development of a Swell Event at Bonga

WASP: Project status

• Seven participants signed up

• Data assembled - being processed to calculate directional spectra and partition into sea and swell components

• Preliminary results in May 03; Final in Q4 03

Analyses

• Comparison of Measurements and Hindcasts

• Scatter Plots of Hs and Tp

• Joint Environmental Contours

• Shape of the Swell Peak in the Power Spectrum

• Directional Characteristics of Swell

• Response Spectra

• Stationarity of the sea state

• Infragravity Waves

Ocean Turbulence Measurements

• Almost no full scale data on turbulence scales of interest

• Spar Responses on 60 - 600 seconds are of interest

• Associated Turbulence Scales are about 60 - 600 m

• Current turbulence data typically is on the scale of 10s to 100s of km, or on very small (mm) scale.

• 15 min current averaging is standard … all turbulence information of interest is lost!

• Ocean Model Basins have difficulty generating low turbulence currents

Ocean Turbulence Measurements

DeepStar Turbulence Program

• Workshop held in Houston November 6-7/02

• Strategies for measurement program identified

• Request for planning letters sent to interested investigators

• Field program planned this year, results in Q1/04

ADCPs & CT sensors on towed fish (RGL Victoria BC)

              

Squall Measurement and Analysis Project

Squalls are thunderstorms

Squalls tend to form along lines

squallwinter storm

Squalls are short-livedbut intense

• Determine the mooring line size for spread moored FPSOs offshore West Africa

• Pose an operational hazard for connecting tankers to CALMS and FPSOs offshore West Africa

• Determine the maximum offset for floating production systems offshore West Africa

• Pose a potential fire hazard due to lightning strikes

Principal knowledge gaps

• Lateral coherence of gusts is unknown

• Assume gusts longer than 1 minute are coherent over the entire length of an FPSO or tanker (conservative?)

laterally coherent gust

laterally uncorrelated gust

Proposed project

• Jointly funded industry project (uniform industry-wide database and procedures)

• Two-year measurement program at EDOP

• Measurements with fine resolution in time and space

• Squall climate at EDOP should be similar to that at Bonga.

• expect 25+ days with significant squall events

• expect at least 10 events with winds > 20m/s

BongaEDOP

The EDOP flare bridge is an ideal “open structure” 370 m long

• Measure horizontal coherence with 5 sensors over 250 m

• Measure vertical profile over most critical elevation range

• High sample rate (1Hz) to resolve all pertinent time scales

• Doppler weather radar to track squall lines

radar

27 m21 m

30 m24 m

18 m

mast

mast

guys

Added cross piece

guys

Existing structure

Cross-sectional view of bridge with notional set up of instrument masts

Original Schedule• Jun 2002 - select consultants, make reconnaissance

trip

• Jul 2002 - issue ITT to bidders

• Aug 2002 - select contractor

• Sep 2002 - submit firm proposal to OPTS

• Oct 2002 - declare project a “go” and award contract

• Jan 2003 - install instruments

• Dec 2004 - complete measurements

• Mar 2005 - complete analyses and deliver report

Safety Guidelines for metocean surveys

• Issues:

• Reduce near-misses while working on vessels

• Sea-worthiness of vessels of opportunity

• Provide level playing field for suppliers

• Help improve standards for companies without metocean engineers

• LIP financed by 6 oil companies

• Developed jointly with companies and suppliers

• In final form, ready for publication as OGP document later Q2/03

WASP (West Africa Swell Project)

Current turbulence measurement GOM

Squall measurement & analysis programme

Safety guidelines for metocean surveys

New version OWP Weather Forecasting

Handbook

EU project: new configuration for altimeter

satellites

Metocean committee activities 2002-4

Not the end - other issues?

Metocean committee activities 2002-4