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Why is scientific work in geohazard important - where does Geohazard fit in to oil business ?. Presented by James M. Strout. Assessment - Prevention - Mitigation. GEOHAZARDS, WHAT ARE THEY?

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Assessment - Prevention - Mitigation

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Assessment prevention mitigation

Why is scientific work in geohazard important - where does Geohazard fit in to oil business?

Presented by James M. Strout

Assessment - Prevention - Mitigation

Assessment prevention mitigation


“Events caused by geological conditions or processes, which represent serious threats for human lives, property or the natural environment”




Slides/debris flows




Slope instability



Shallow gas/hydrates


Assessment prevention mitigation

INTERNATIONAL CENTRE FOR GEOHAZARDSAssessment, prevention, mitigation and management

ICG vision:

Develop knowledge that can help save lives and reduce material and environmental damage.

To be, within 5 to 8 years, the world authority and the premier research group on geo-related natural hazards, with special emphasis on slide hazards, both on land and offshore.

Partners in centre of excellence



    • Norwegian Geotechnical Institute (NGI)


    • University of Oslo (UiO)

    • NTNU

    • Geological Survey of Norway (NGU)

    • NORSAR

Assessment prevention mitigation

Wave generation



Retrogressive sliding

Mud volcano

Debris flow

Gas hydrates or free gas

Gas chimney




Diapirism Doming


Offshore geohazards

Focus on underwater slope stability

Focus on underwater slope stability

  • Field development on the continental slopes

  • Enormous historic and paleo slides observed

  • Large runout distances, retrogressive sliding upslope/laterally and tsunami generation may threaten 3rd parties in large areas

The Ormen lange field illustrates the importance of a geohazard study

Assessment prevention mitigation

The Storegga Slide (8200 ybp)

Ormen Lange

Field development was contingent on the results of the geohazards study. It was necessary to:

- understand the Storegga slide

- survey, sample, test and monitor to characterise site

- develop failure mechanisms and models

- evaluate the present day stability conditions

These studies resulted in the conclusion that the present day slopes were stable, and the site was safe for development.

Headwall 300 km

Run-out  800 km

Volume  5.600 km3

Area  34.000 km2

Geohazards study elements

Geohazards study – elements

  • Site investigation (geophysical, geological & geotechnical)

  • Assess in situ conditions and material properties

  • Define relevant and critical geo-processes

  • Assess interaction of processes

  • Identify failure mechanisms

  • Identify trigger mechanisms

Geohazards study assessment

Geohazards study – Assessment

  • Overall geological understanding of site

  • Assessment of probability of occurence

  • Calculate/predict consequences

  • Uncertainties:

    • Limited site investigations, measurement and test data

    • Modelling of processes and mechanisms

Monitoring and measuring

Monitoring and measuring

  • Key parameters needed

    • Seismic survey and metaocean data

    • Geological structures, history, sedimentation rates

    • Pore pressure and mechanical behaviour of the soil

    • Inclination/movement/settlement/subsidence

    • Gas releases or seepages

    • Vibrations/earthquakes

    • + + +

  • Time dependent variable?

    • ’Snapshot’ measurement w/o time history

    • Monitoring w/ time history, e.g. to capture natural variations, or effects caused by construction/production activity

  • Timing: before, during and after field development

Closing comments

Closing comments

  • Consequences of geohazard events can be very large, in terms of both project risk and 3rd party risk

  • Thorough understanding of natural and human induced effects is needed in order to identify the failure scenarios relevant for field development

  • Geohazard assessment require multi-discipline geoscience cooperation and understanding

Purpose of geohazards research

Purpose of geohazards research

  • improve ourunderstanding of why geohazards happen.

  • assess the risks posed by geohazards.

  • prevent the risks when possible.

  • mitigate and manage the risks when it is not possible to prevent them.

Thank your for your attention

Thank your for your attention!

Overheads illustrating each element of a geohazard study

Overheads illustrating each element of a geohazard study

Geophysical investigation improved imaging techniques

Geophysical investigationImproved imaging techniques

Assessment prevention mitigation

In situ conditions and material propertiesCorrelation of geological, geotechnical, and geophysical parameters

Assessment prevention mitigation



Sealevel change









Stress/pressure: p, s, u, s’

Defining critical geo-processes1D Basin model for Pressure-Temperature time history during geological time

Deposition rate


p=hydr. water pressure

u=pore pressure

s=vertical soil stress

s’=eff. soil stress

Contributing processes interaction gas hydrate melting caused by climate change after deglaciation

BGHSZ at LGM sea level at -130m m

Potential zone of GH melting

BGHZ after intrusion

of warm atlantic surface water

BGHSZ after sea level rise

Contributing processes/interactionGas hydrate melting caused by climate change after deglaciation

Geothermal gradient 50C/km

Failure mechanism retrogressive sliding

Failure mechanismRetrogressive Sliding

  • Development of material and mechanical models required for explanation of failure on low slope angles

  • High excess pore pressure and/or strain softening (brittleness) required

  • Local downslope failure (slumping) need to be triggered for initation of large slide

Triggering mechanisms earthquake analysis





Depth belom mudline, m

Depth belom mudline, m

Max. pore pressure ratio after event, %

Max. displacement, cm

Triggering mechanisms Earthquake analysis

  • 1D site response analysis of infinite slope

  • Material model for cyclic loading includes pore pressure generation, cyclic shear strain, accumulated shear strain

  • Pore pressure redistribution and dissipation after earthquake

Overall geological understanding ormen lange the entire geo conditions leading to instability

Overall geological understandingOrmen lange: the entire “geo-conditions” leading to instability

Assessment prevention mitigation

Evaluate consequencesTsunami modelling and prediction

Evaluating probabilities

Evaluating probabilities

  • Variability/incompleteness of data

  • Modelling errors

  • Recurrence of triggering mechanisms

  • Presence of necessary conditions

  • + + +

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