Geohazard Assessment for Deepwater Development A Multi-Disciplinary, Integrated Approach Stephen Wardlaw20 October 2011

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Geohazard Assessment for Deepwater Development A Multi-Disciplinary, Integrated ApproachOBJECTIVES 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

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Deepwater Environment East Coast India

After Bastia et al. (2011)

Regional BathymetryStephen Wardlaw

Regional Dip Map3

Deepwater Geohazards East Coast IndiaSubmarine canyons and channels

Gas Hydrates (BSR)

After Bastia et al. (2011)

Sediment WavesStephen Wardlaw

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Deepwater Geohazards East Coast IndiaMonsoon Winds - July

Ocean Currents

Seismic Hazard

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Deepwater Conditions East Coast India

Typical Deepwater HazardsStephen Wardlaw

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Deepwater Geohazard RegisterGeologic Feature Steep Slopes Active Channels/Canyons Rough seafloor topography Mobile sediments (sand waves) Seafloor Currents Gas Hydrates Hydrocarbon venting Earthquakes Active faults Storms (wind/waves) Potential Hazard/Constraint Unstable base, slope failures Turbidity Flows, Debris Flows Pipeline spans, unsuitable base Unstable base Erosion, Scour Dissociation leading to loss of soil strength, foundation strain Unstable sediments, authigenic carbonate buildup Soil liquefaction, slope failure trigger Local shear, gas conduit Impact to risers/topsides, slope failure trigger7

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Geohazard Assessment Sequence

Desktop study Black hole

Geophysics

Engineering Design Integrated Interpretation Boreholes Testing

CPT

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Geohazard Assessment Sequence

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Multi-Disciplinary IntegrationPublic Domain Metocean

Ground Model GIS Database Geophysical Data

Geotechnical Data Engineering Analysis Analogous Sites/ Previous Experience

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Geohazard Assessment Sequence Regional Desktop StudiesGeophysical /Public Domain Data

Regional Geohazard Inventory

Regional Favorability Chart

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Geohazard Assessment Sequence Regional Desktop StudiesMetocean Desktop Study

Probabilistic Seismic Hazard Analysis (PSHA)

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Geohazard Assessment Sequence Geophysical SurveysSub-bottom Profiler (SBP)

AUV Surveys Side-scan Sonar (SSS)

Bathymetry

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Geohazard Assessment Sequence Geotechnical Sampling/TestingBox Cores

Drillship

Borings

In-situ Testing (CPT)

Jumbo Piston Coring

Laboratory Testing

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Geohazard Assessment Sequence Integrated Interpretation

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Geohazard Assessment Sequence Integrated Interpretation

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Geohazard Assessment Sequence Specialist AnalysisAges of Low-to- 0 High Sea Level Transitions 1 Oxygen Isotope Stage

1 2

M1 (~14.9 ka)

13.7 ka2

28+4 ka

M2 (~19.8 ka) M3 (~22.5 ka)

3 4

35

M4 (~23.8 ka)

59+4 ka 75+5 ka

6 7 8 9 100

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Carbon-14 Sample Locations from a Stratigraphic Reference M5 ( 75 ka) CoreM6 (~75 ka)

5110 120

125+5 ka130 140

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Fault History AnalysisStephen Wardlaw

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Geohazard Assessment Sequence Risk Assessment

Risk Analysis Matrix

Mudflow Susceptibility Map

Impact AssessmentStephen Wardlaw

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Geohazard Assessment Sequence Engineering Design (Pipeline Modeling)

Soil-Pipe Interaction Stephen Wardlaw

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Geohazard Assessment Sequence Engineering Design (Suction Anchors)

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Geohazard Assessment Sequence

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Geohazard Assessment Sequence

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Geohazard Assessment for Deepwater Development A Multi-Disciplinary, Integrated ApproachCONCLUSIONS 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

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