Exploitation of Ocean Predictions by the Oil and Gas ...godae-data/Symposium/GOV...Exploitation of Ocean Predictions by the Oil and Gas Industry GODAE OceanView Symposium 2013 Introduction

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?

Exploitation of Ocean Predictions by the Oil and Gas ...godae-data/Symposium/GOV...Exploitation of Ocean Predictions by the Oil and Gas Industry GODAE OceanView Symposium 2013 Introduction

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