www.fugro.com

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

2

Stephen Wardlaw

Deepwater Environment – East Coast India

3

Regional Bathymetry Regional Dip Map

After Bastia et al. (2011)

Stephen Wardlaw

Deepwater Geohazards – East Coast India

4

Submarine canyons and channels

Sediment Waves

After Bastia et al. (2011)Gas Hydrates (BSR)

Stephen Wardlaw

Deepwater Geohazards – East Coast India

5

Seismic Hazard

Monsoon Winds - July

Ocean Currents

Stephen Wardlaw

Deepwater Conditions – East Coast India

6

Typical Deepwater Hazards

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

Stephen Wardlaw

Geohazard Assessment Sequence

8

Desktop study

Black hole…Geophysics

CPT

BoreholesTestingIntegrated Interpretation

Engineering Design

Stephen Wardlaw

Geohazard Assessment Sequence

9

Stephen Wardlaw

Multi-Disciplinary Integration

10

Ground Model

Metocean

GIS Database

Analogous Sites/Previous Experience

Engineering Analysis

Geotechnical Data

Geophysical Data

Public Domain

Stephen Wardlaw

Geohazard Assessment SequenceRegional Desktop Studies

11

Geophysical /Public Domain Data

Regional Geohazard Inventory

Regional Favorability Chart

Stephen Wardlaw

Geohazard Assessment SequenceRegional Desktop Studies

12

Metocean Desktop Study

Probabilistic Seismic Hazard Analysis (PSHA)

Stephen Wardlaw

Geohazard Assessment SequenceGeophysical Surveys

13

Bathymetry

AUV Surveys

Sub-bottom Profiler (SBP)

Side-scan Sonar (SSS)

Stephen Wardlaw

Geohazard Assessment SequenceGeotechnical Sampling/Testing

14

Drillship

Jumbo Piston Coring

Borings

In-situ Testing (CPT)

Box Cores

Laboratory Testing

Stephen Wardlaw

Geohazard Assessment SequenceIntegrated Interpretation

15

Stephen Wardlaw

Geohazard Assessment SequenceIntegrated Interpretation

16

Stephen Wardlaw

Geohazard Assessment SequenceSpecialist Analysis

17

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

Stephen Wardlaw

Geohazard Assessment SequenceRisk Assessment

18

Risk Analysis Matrix

Mudflow Susceptibility MapImpact Assessment

Stephen Wardlaw

Geohazard Assessment SequenceEngineering Design (Pipeline Modeling)

19

Soil-Pipe Interaction

Stephen Wardlaw

Geohazard Assessment SequenceEngineering Design (Suction Anchors)

20

Stephen Wardlaw

Geohazard Assessment Sequence

21

Stephen Wardlaw

Geohazard Assessment Sequence

22

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