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Geohazard Assessment for Deepwater Development –A Multi-Disciplinary, Integrated Approach
Stephen Wardlaw20 October 2011
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
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Deepwater Environment – East Coast India
3
Regional Bathymetry Regional Dip Map
After Bastia et al. (2011)
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Deepwater Geohazards – East Coast India
4
Submarine canyons and channels
Sediment Waves
After Bastia et al. (2011)Gas Hydrates (BSR)
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Deepwater Geohazards – East Coast India
5
Seismic Hazard
Monsoon Winds - July
Ocean Currents
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Deepwater Conditions – East Coast India
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Typical Deepwater Hazards
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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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Geohazard Assessment Sequence
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Desktop study
Black hole…Geophysics
CPT
BoreholesTestingIntegrated Interpretation
Engineering Design
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Geohazard Assessment Sequence
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Multi-Disciplinary Integration
10
Ground Model
Metocean
GIS Database
Analogous Sites/Previous Experience
Engineering Analysis
Geotechnical Data
Geophysical Data
Public Domain
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Geohazard Assessment SequenceRegional Desktop Studies
11
Geophysical /Public Domain Data
Regional Geohazard Inventory
Regional Favorability Chart
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Geohazard Assessment SequenceRegional Desktop Studies
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Metocean Desktop Study
Probabilistic Seismic Hazard Analysis (PSHA)
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Geohazard Assessment SequenceGeophysical Surveys
13
Bathymetry
AUV Surveys
Sub-bottom Profiler (SBP)
Side-scan Sonar (SSS)
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Geohazard Assessment SequenceGeotechnical Sampling/Testing
14
Drillship
Jumbo Piston Coring
Borings
In-situ Testing (CPT)
Box Cores
Laboratory Testing
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Geohazard Assessment SequenceIntegrated Interpretation
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Geohazard Assessment SequenceIntegrated Interpretation
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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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Geohazard Assessment SequenceRisk Assessment
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Risk Analysis Matrix
Mudflow Susceptibility MapImpact Assessment
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Geohazard Assessment SequenceEngineering Design (Pipeline Modeling)
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Soil-Pipe Interaction
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Geohazard Assessment SequenceEngineering Design (Suction Anchors)
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Geohazard Assessment Sequence
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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
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