exploitation of ocean predictions by the oil and gas ...godae-data/symposium/gov...exploitation of...

Exploitation of Ocean Predictions by the Oil and Gas Industry

GODAE OceanView Symposium 2013

Introduction

Information needs

Challenges

Acknowledgements

• IMarEST/SUT Metocean Awareness Course

• Colleagues across the metocean services industry

Introduction

Information needs

Challenges

Offshore Lease Appraisal

• Identify technical & financial risks

• Estimate potential cost of field development

• Metocean information needs:

– Basic classification of metocean environment

– Highlight risks/hazards e.g. strong currents

Offshore Seismic & Site Surveys

• Seismic - initial exploration & 4D over field life

• Site Surveys – prior to drilling & for field development

• Metocean limitations - sea state and variable

currents

• Sea state - limits deployment & recovery, operations,

noise

• Cross-currents – feathering angle

– Optimise survey line orientation

– Variable angle with changes in current speed &

direction

Offshore Seismic & Site Surveys

• During the Survey:

– Site & application specific wind & wave forecasts

– Current forecasts where currents are an operational

constraint

Offshore Exploration & Appraisal Drilling

Feasibility:

• Initial Desk study to identify

– Metocean conditions &

processes

– Significant hazards (tropical

cyclones, strong currents)


Rig Selection, Mooring & Riser Design:

• Wind & wave monthly statistics – potential downtime

– Average, good and bad years

Significant Wave Height (Hs)

Percentage Exceedence


Rig Selection, Mooring & Riser Design:

• Extreme event criteria & current profile

– Selection of return period for mooring design


Drilling:

• Site-specific weather forecasts

• Current forecasts (in locations

where currents may be an

operational constraint, eg GoM)

Offshore Field Development Concept

Selection influenced by:

• Field characteristics

• Water depth

• Metocean conditions……

Source: Options to produce deepwater oil, gas to proliferate, Guntis Moritis, Oil &

Gas Journal, December 13, 1999.

Fixed Offshore Structures Limit State Design

• Wind, wave, current criteria:

• 1, 10, 50 & 100, return period

• Design: 100 yr with 1% annual probability of occurrence

• Over 30 year field life, 26% chance 100 yr value exceeded.

Accidental Limit State (ALS) design

• 1,000 and 10,000 yr return period values

• Also used to determine air gap

Response Based Design

• Joint wind/wave/current/surge criteria

• Equating to 100 yr load

Fatigue Assessment

• Wave height vs wave period scatter diagrams

• Directional frequency of occurrence

Towing & Installation of Offshore Structures

& Topsides

• Metocean Impact on:

– Installation method

– Barge selection

– Design of sea fastenings

– Tow route

• Hazards

– Long period waves

– Wave height

– Cross seas

– Strong currents

– Wind/wave/current

offsets


& Topsides

Operational Planning for Tow & Installation:

– Wind & wave monthly statistics – potential downtime

• Average, good and bad years

– Persistence analysis


& Topsides

Ocean Tow and Installation Design Aspects:

• Assess Metocean hazards en route & at

site

• Metocean criteria for tow route and

installation site

• Assessment of fatigue loading for tow &

installation

• Wind, wave and current data for float-over

vessel motion computations


& Topsides

Tow & Installation:

• Tow-specific and site-specific wind and

wave forecasting

• Real-time wind and directional sea state

monitoring

• Barge motion monitoring

• Current forecasting and real-time current

measurement where the flow regime is

complex

Floating Production Systems

Metocean Factors:

• Response to joint wind, wave &

current conditions

– Design

– Operability

– Tanker offloading

Floating Production Systems System Design/Selection - Conceptual design:

• Input: Winds, waves & currents (profile)

– Extremes by direction & month

– Operational statistics by direction & month

• Split directional wave spectra into wind-sea and

swell components

• Directional offsets between incident currents,

waves and winds

• Determine vessel alignment & motions using

response model

• Ambient and extreme sea temperatures through

the water column

Ship Heading

Wind

9.4 m/s

Wind-sea

3.0 m, 6.9 s

Swell

2.8 m, 12.7 s

Current

0.13m/s

Floating Production Systems

Offshore Installation:

• Wind, wave and current statistics for planning

– Monthly percentage exceedence


– by month in average, good and bad years;

• For subsea & mooring installation, & vessel hook-up

– Metocean measurements

– site-specific weather and current forecasts;

• Operation:

– Real-time current & wave measurements;

– Site-specific weather (& current) forecasts.

Subsea, Pipelines & Cables

Near-Shore and Landfall Design:

• Tide & Surge

• Shore approach design waves & currents

• Extreme wave run-up level at shoreline for bund design

• Assessment of sediment and coastline stability

• Extreme and ambient near-bed temperatures


Shallow & deepwater design:

• Extreme near bed wave-induced and

current velocities (directional)

• Joint wave and current data for response-

based design analysis

– Directional metocean criteria optimised on

on-bottom pipeline stability

• Bottom sediment stability

• Extreme and ambient near-bed

temperatures


Installation & repair:

• Wind, wave & current statistics for

planning and optimising pipelaying

barge selection:

– Monthly percentage exceedence


– Weather windows analysis

– by month in average, good and bad

years


Installation & repair:

• Real-time metocean data

• Site-specific weather (& current) forecasts.

Coastal Facilities Jetty Design:

• Wind, wave, current & water level

statistics by month

– average, bad and good years

• Long period wave energy

– Infra-gravity waves

• Vessel response to metocean conditions

– safety & potential downtime

• Sediment transport

– dredging & scour

• Extremes and for design

• Structure, deck elevation, piles

Coastal Facilities

Coastal Protection:

• Normal and extreme conditions:

– near-shore waves by direction

– water levels;

– Joint occurrence wave & water levels

Marine Cooling Water and Desalination

Systems:

• Monthly mean, maximum and minimum sea

water temperatures

• Local circulation

Offshore Operations (Logistics)

– Oil & Gas Production

– Aviation

– Vessels

– ROV/AUV operations

– Oil spill contingency

Metocean deliverables:

– Metocean Operational Planning

Statistics

– Real-Time Metocean Measurements

– Forecasts


Wind, wave & current statistics for planning & optimisation:

• by month in average, good and bad years

• downtime persistence

Significant Wave Height (Hs)

Percentage Exceedence matrix


Offshore Weather Forecasts:

Decommissioning

Metocean Requirements

• Design extremes

• Operational statistics

• Forecasts

Introduction

Information needs

Challenges

Ocean predictions and the oil & gas industry

• Ocean predictions have essentially three types of use:

– Reanalysis/hindcast products to support determining design criteria and particularly extreme design conditions

– Reanalysis products/hindcasts to support operational planning and evaluation of operational risks

– Forecasts to support real time operations, short term planning and emergency response

How useful are present ocean predictions? Ocean winds

• Generally acceptable quality for short term forecasts and as custom reanalyses for specific basins

• Challenges:

• Squall forecasts

• New basins

• Climate change

Shell’s Kulluk drilling rig grounded

just off the coast Sitkalidak Island,

near Kodiak Island, after running

loose when towed during a near

hurricane-strength storm on 27

Dec.2012

How useful are present ocean predictions? Waves

• Generally acceptable quality for both short term forecasts and as hindcast databases. Suitable calibration with measured data permits use for design studies and operability analyses.

• Challenges:

• Long period swells

• Internal waves

• New basins

• Climate change

How useful are present ocean predictions? Currents

• Hindcasts frequently miss peak events when compared to measured data. Some skill in certain regions on a climatological basis. Used with care by the industry, for design studies; often after calibration & adjustment

• Limited site specific forecast skill

• Challenges: • Hindcast skill improvements

sufficient to reduce need for site-specific measurements

• Improved forecast skill

How useful are present ocean predictions? Other variables

• Temperatures & Salinity

– Industry not a major user. Hindcast archives used for design (flow assurance issues – hydrate formation etc). Oil spill weathering issues

• Sea ice hindcasts/forecasts

– Growing importance with progressive moves towards increased Arctic exploration and production

Conclusions

• Wind and wave reanalysis/hindcast and short-term forecast products generally fit for purpose

• Moving towards sufficiently skilled current hindcasts for major oil and gas basins

• Challenges remain with delivery of adequate short-term current forecasts in some regions

• Need to address requirements in new exploration and production regions (eg Arctic/Southern Ocean)

• Challenges with effective use of climate projections

38

Questions Thank You

Questions?

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