Transcript West Africa Swell Project (WASP)

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
Metocean Committee
2002-4 activities
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
West Africa Swell Project (WASP)
•
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
Development of a Swell Event offshore
Nigeria
19 July 1998
1200
10
1400
Power (m2 sec)
8
1600
1800
6
2000
4
2
0
0.0
0.1
Frequency
0.2
Development of a Swell Event at Bonga
Distance to storm = 9000 km
25
Peak Period (sec)
20
15
10
5
0
0
20
40
60
Elapsed Time (hr)
80
100
120
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
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Directional Characteristics of Swell
•
Response Spectra
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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
winter
storm
Squalls are
thunderstorms
Squalls tend to form
along lines
squall
Squalls are short-lived
but 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
Bonga
EDOP
•
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
The EDOP flare bridge is an ideal “open structure” 370 m long
radar
30 m
24 m
27 m
21 m
18 m
•
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
mast
Existing
structure
guys
mast
Added cross piece
guys
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
Metocean committee activities 2002-4
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?