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THE 4Gs IN PRACTICE: INVESTIGATING HOW THE 4Gs ARE APPLIED IN THE OIL & GAS INDUSTRY Society for Underwater Technology, Evening Technical Meeting 14 AUGUST 2013 GEOPHYSICS & PORT DEVELOPMENTS EXPLORING MARINE & TRANSITION ZONES

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THE 4Gs IN PRACTICE: INVESTIGATING HOW THE 4Gs ARE APPLIED IN THE OIL & GAS INDUSTRY

Society for Underwater Technology, Evening Technical Meeting 14 AUGUST 2013

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Commercial in Confidence – 2

GEOPHYSICS & PORT DEVELOPMENTS – EXPLORING MARINE & TRANSITION ZONES

Dr Kathleen McMahon

Senior Geophysicist, GroundProbe

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Commercial in Confidence – 3

SUMMARY

  • WHY USE GEOPHYSICS?
  • MARINE GEOPHYSICAL TECHNOLOGIES
  • THE PROS & CONS
  • EXAMPLE RESULTS & CASE STUDIES
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Commercial in Confidence – 4

WHY USE GEOPHYSICS?

Geophysics is a useful tool for pre-development investigations in the marine environment and within the

  • nshore/offshore transition zone
  • What? Dredging, Piling, Causeways, Reclamation,

Pipelines

  • When? Pre-planning, Pre- or post-drilling activities
  • Where? Near shore (shallow) marine, Land, Transition

zones

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Commercial in Confidence – 5

WHY USE GEOPHYSICS?

  • Why? Geophysics can assist with:
  • Determination of suitable locations for berths, turning

pockets and approach channels

  • Identifying dredgeable areas
  • Providing geotechnical or geohazard information –

e.g. impediments to dredging such as hard ridges

  • Providing layer information & depth to bedrock
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Commercial in Confidence – 6

WHY USE GEOPHYSICS?

  • Products:
  • Layer mapping of geophysical boundaries along

transects, and 3D surface modelling

  • Correlation with lithology data (borehole/vibrocore)
  • Geophysical unit characterisation – geophysical

properties, thickness/depth, dominant lithologies

  • Volume estimation
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Commercial in Confidence – 7

MARINE GEOPHYSICAL TECHNOLOGIES

  • Marine Surveying in Shallow (<30 m) Water:
  • Bathymetry & Side Scan Sonar
  • Magnetics
  • Seismic Reflection
  • Seismic Refraction
  • Electrical Methods
  • Transition Zone & Land-based surveying:
  • Seismic Methods – Refraction, MASW, Reflection
  • Electrical Methods – Electrical Resistivity Imaging (ERI)
  • Electromagnetic (EM) Methods – Shallow EM
  • And more…
  • Airborne Electromagentics
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Commercial in Confidence – 8

THE PROS & CONS

TECHNOLOGY TYPE OF METHOD POSITIVES NEGATIVES

Seismic Reflection (CSP – Continuous Seismic Profiling) Seismic Provides structural information (layers, depths) Fast acquisition Does not produce hardness information Seismic Refraction Seismic Established correlation between P-wave velocity and dredgeability Cannot detect velocity inversions (low velocity layers between higher velocity layers) MASW (Multi- channel Analysis of Surface Waves) Seismic Can detect velocity inversions . Horizontal resolution reduced Frequency- dependant Resistivity Electrical Maps porosity and clay variations Does not produce hardness information Low resolution

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Commercial in Confidence – 9

THE PROS & CONS

TECHNOLOGY TYPE OF METHOD POSITIVES NEGATIVES

Magnetics Potential Fields Detects iron (metallic objects) Can map magnetic geologic units Does not provide depth discrimination Side Scan Sonar Sonar Detects seafloor features e.g. sand structures, coral,

  • bstructions

Seafloor surface

  • nly

MBES (Multi-Beam Echo-Sounder) Bathymetry Provides detailed bathymetry . Seafloor surface

  • nly

SkyTEM Airborne Electromagnetics Fast coverage No hardness information Low resolution

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Commercial in Confidence – 10

MARINE SEISMIC

  • Seismic Reflection
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Commercial in Confidence – 11

MARINE SEISMIC

  • Seismic Refraction vs MASW
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Commercial in Confidence – 12

MARINE SEISMIC – PORT DEVELOPMENT CASE STUDY 1

  • Defining layers & stiffness/velocity variations
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Commercial in Confidence – 13

MARINE SEISMIC – PORT DEVELOPMENT CASE STUDY 1

  • Defining layers & stiffness/velocity variations
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Commercial in Confidence – 14

MARINE SEISMIC – PORT DEVELOPMENT CASE STUDY 1

80ms 0ms 0mBSL

≈10mBSL

0km 1km

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Commercial in Confidence – 15

MARINE SEISMIC – PORT DEVELOPMENT CASE STUDY 1

  • Dredgeability

P-WAVE VELOCITY DREDGING CHARACTERI STICS COLOUR (IN IMAGE)

1530 – 1900 Easily dredged with a TSHD1 GREEN 1900 – 2500 Easily dredged with a CSD2 YELLOW 2500 – 4000 Dredge with difficulty with a CSD2 ORANGE . > 4000 Blasting required RED

1TSHD - Trailing Suction Hopper Dredger 2CSD - Cutting Suction Dredger

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Commercial in Confidence – 16

MARINE SEISMIC – PORT DEVELOPMENT CASE STUDY 2

  • 3D Surfaces, Volumes, Layer Characterisation
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Commercial in Confidence – 17

MARINE SEISMIC – PORT DEVELOPMENT CASE STUDY 2

  • 3D Surfaces, Volumes, Layer Characterisation
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Commercial in Confidence – 18

MARINE SEISMIC – PORT DEVELOPMENT CASE STUDY 2

  • 3D Surfaces, Volumes, Layer Characterisation
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Commercial in Confidence – 19

SHALLOW MARINE AND NEAR SHORE RESISTIVITY

  • Onshore & Offshore Electrical Resistivity Imaging
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Commercial in Confidence – 20

AIRBORNE ELECTROMAGNETICS OVER MARINE- LAND TRANSITION

  • Mapping clays & fresh vs saline groundwater

Clay lens Fresh water saturated Saline water saturated

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Commercial in Confidence – 21

THANK YOU