slide1
Download
Skip this Video
Download Presentation
Assessment - Prevention - Mitigation

Loading in 2 Seconds...

play fullscreen
1 / 23

Assessment - Prevention - Mitigation - PowerPoint PPT Presentation


  • 111 Views
  • Uploaded on

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?

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' Assessment - Prevention - Mitigation' - zan


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
slide1

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

Presented by James M. Strout

Assessment - Prevention - Mitigation

slide2

GEOHAZARDS, WHAT ARE THEY?

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

Onshore

Volcanism

Earthquakes

Slides/debris flows

Floods

Avalanches

Offshore

Slope instability

Earthquakes

Tsunamis

Shallow gas/hydrates

Diapirism

slide3

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
PARTNERS IN CENTRE OF EXCELLENCE
  • HOST ORGANISATION
    • Norwegian Geotechnical Institute (NGI)
  • PARTNERS
    • University of Oslo (UiO)
    • NTNU
    • Geological Survey of Norway (NGU)
    • NORSAR
slide5

Wave generation

Tsunami

Tsunami

Retrogressive sliding

Mud volcano

Debris flow

Gas hydrates or free gas

Gas chimney

Earth-quake

Underground

blowout

Diapirism Doming

Overpressure

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

slide7

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.
slide16
In situ conditions and material propertiesCorrelation of geological, geotechnical, and geophysical parameters
slide17

h(t)

z

Sealevel change

time

Dt

s’

Du

p

u

s

T

Stress/pressure: p, s, u, s’

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

Deposition rate

T=temperature

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

0.05g

0.10g

0.20g

0.30g

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
evaluating probabilities
Evaluating probabilities
  • Variability/incompleteness of data
  • Modelling errors
  • Recurrence of triggering mechanisms
  • Presence of necessary conditions
  • + + +
ad