session4 stephanwardlaw fugro [compatibility mode]
TRANSCRIPT
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Geohazard Assessment for Deepwater Development –A Multi-Disciplinary, Integrated Approach
Stephen Wardlaw20 October 2011
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OBJECTIVES
1. Review various geohazards that may impact deepwater development
2. Identify geoscience disciplines that can contribute to geohazard assessment
3. Illustrate idealized sequence of geohazard assessment tasks within project development process
Stephen Wardlaw
Geohazard Assessment for Deepwater DevelopmentA Multi-Disciplinary, Integrated Approach
2
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Stephen Wardlaw
Deepwater Environment – East Coast India
3
Regional Bathymetry Regional Dip Map
After Bastia et al. (2011)
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Stephen Wardlaw
Deepwater Geohazards – East Coast India
4
Submarine canyons and channels
Sediment Waves
After Bastia et al. (2011)Gas Hydrates (BSR)
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Stephen Wardlaw
Deepwater Geohazards – East Coast India
5
Seismic Hazard
Monsoon Winds - July
Ocean Currents
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Stephen Wardlaw
Deepwater Conditions – East Coast India
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Typical Deepwater Hazards
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Stephen Wardlaw
Deepwater Geohazard Register
7
Geologic Feature Potential Hazard/ConstraintSteep Slopes Unstable base, slope failuresActive Channels/Canyons Turbidity Flows, Debris FlowsRough seafloor topography Pipeline spans, unsuitable baseMobile sediments (sand waves)
Unstable base
Seafloor Currents Erosion, ScourGas Hydrates Dissociation leading to loss of soil strength,
foundation strain Hydrocarbon venting Unstable sediments, authigenic carbonate buildupEarthquakes Soil liquefaction, slope failure triggerActive faults Local shear, gas conduitStorms (wind/waves) Impact to risers/topsides, slope failure trigger
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Stephen Wardlaw
Geohazard Assessment Sequence
8
Desktop study
Black hole…Geophysics
CPT
BoreholesTestingIntegrated Interpretation
Engineering Design
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Stephen Wardlaw
Geohazard Assessment Sequence
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Stephen Wardlaw
Multi-Disciplinary Integration
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Ground Model
Metocean
GIS Database
Analogous Sites/Previous Experience
Engineering Analysis
Geotechnical Data
Geophysical Data
Public Domain
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Stephen Wardlaw
Geohazard Assessment SequenceRegional Desktop Studies
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Geophysical /Public Domain Data
Regional Geohazard Inventory
Regional Favorability Chart
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Stephen Wardlaw
Geohazard Assessment SequenceRegional Desktop Studies
12
Metocean Desktop Study
Probabilistic Seismic Hazard Analysis (PSHA)
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Stephen Wardlaw
Geohazard Assessment SequenceGeophysical Surveys
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Bathymetry
AUV Surveys
Sub-bottom Profiler (SBP)
Side-scan Sonar (SSS)
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Stephen Wardlaw
Geohazard Assessment SequenceGeotechnical Sampling/Testing
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Drillship
Jumbo Piston Coring
Borings
In-situ Testing (CPT)
Box Cores
Laboratory Testing
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Stephen Wardlaw
Geohazard Assessment SequenceIntegrated Interpretation
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Stephen Wardlaw
Geohazard Assessment SequenceIntegrated Interpretation
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Stephen Wardlaw
Geohazard Assessment SequenceSpecialist Analysis
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1
2
3
6
4
5
1
2
3
4
5
6
7
8
9
100
0
110
120
130
140
Oxygen IsotopeStage
M4 (~23.8 ka)
M3 (~22.5 ka)
M2 (~19.8 ka)
M1 (~14.9 ka)
M6 (~75 ka)
M5 (<24, > 75 ka)
1
2
3
6
4
5
1
2
3
4
5
6
7
8
9
100
0
110
120
130
140
125+5 ka
75+5 ka
59+4 ka
28+4 ka
13.7 ka
Ages of Low-to-High Sea Level
Transitions
Carbon-14 Sample Locations from a
Stratigraphic Reference Core
Fault History Analysis
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Stephen Wardlaw
Geohazard Assessment SequenceRisk Assessment
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Risk Analysis Matrix
Mudflow Susceptibility MapImpact Assessment
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Stephen Wardlaw
Geohazard Assessment SequenceEngineering Design (Pipeline Modeling)
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Soil-Pipe Interaction
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Stephen Wardlaw
Geohazard Assessment SequenceEngineering Design (Suction Anchors)
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Stephen Wardlaw
Geohazard Assessment Sequence
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Stephen Wardlaw
Geohazard Assessment Sequence
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CONCLUSIONS
1. Significant potential geohazards affecting deepwater development offshore India are widespread
2. Start process early in the project life cycle to have maximum cost-effective impact on project
3. Follow recommended sequence of tasks
4. Multi-disciplinary, integrated approach is key to success
Stephen Wardlaw
Geohazard Assessment for Deepwater DevelopmentA Multi-Disciplinary, Integrated Approach
23